Phytoremediation A Novel Strategy for the Removal of Toxic Metals from the Environment Using Plants

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重金属污染英语

Heavy metal pollution refers to the environmental pollution caused by heavy metals or their compounds.It tend to be enrichment.And it is hard to be broken down in the environment.
what happened these years in China ？
Q：Where does it come from？
A: Pollution by emission
Pollution from industry emission is the main source of heavy metal pollution in China. In coal burning areas, the different contents of heavy metals in the coal have affected the emission of heavy metals into the atmosphere.
Arsenic: is one of the components of arsenic（砒霜）, highly toxic and can cause person quickly die. Long-term exposure to small amounts, can cause chronic poisoning（慢性中毒）. There are also carcinogenic（致癌）。
In 2010,many children were found to blood lead levels.( 血铅超标)
In 2011，over 300 people were found to blood lead leavels because of the local battery enterprises pollution.(当地电池企业污染)

英语环境科学英语40题

英语环境科学英语40题1. Which of the following is a renewable resource?A. CoalB. OilC. WindD. Natural gas答案：C。

本题考查可再生资源的概念。

选项 A 煤炭、选项 B 石油和选项 D 天然气都是不可再生资源，而选项 C 风能是可再生资源。

2. What causes air pollution?A. PlantsB. Clean waterC. Factory emissionsD. Beautiful scenery答案：C。

本题考查造成空气污染的原因。

选项A 植物有助于净化空气；选项 B 清洁的水与空气污染无关；选项 D 美丽的风景也不会导致空气污染；而选项C 工厂排放物会造成空气污染。

3. Which of the following is not a way to save water?A. Taking short showersB. Leaving the tap runningC. Fixing leaky faucetsD. Using a bucket to wash the car答案：B。

本题考查节约用水的方法。

选项 A 缩短淋浴时间、选项 C 修理漏水的水龙头和选项 D 用桶洗车都是节约用水的方式；选项B 让水龙头一直开着会浪费水。

4. What is the main cause of deforestation?A. Planting more treesB. Building housesC. WildfiresD. Logging for wood答案：D。

本题考查森林砍伐的主要原因。

选项A 种植更多树木是保护森林；选项B 建造房屋不是主要原因；选项C 野火可能导致部分树木受损，但不是主要的砍伐原因；选项D 为获取木材而伐木是导致森林砍伐的主要原因。

5. Which of the following is a greenhouse gas?A. OxygenB. NitrogenC. Carbon dioxideD. Hydrogen答案：C。

植物对河道污染沉积物中重金属的修复

植物对河道污染沉积物中重金属的修复李红霞;赵新华;马伟芳【摘要】针对河道沉积物中的重金属污染问题,采用温室栽培试验研究了黑麦草对河道污染沉积物中重金属Ni,Cu和Cd的修复效果.结果表明:3种重金属在黑麦草地上部分的累积量均小于地下部分,其中Ni地上部分为63.014mg·kg-1,为沉积物中Ni总量的1/3;Cu地上部分为92.356mg·kg1,约占Cu总量的1/5;Cd地上部分为1.449 mg·kg-1,占Cd总量的1/4.地上部分累积的重金属量与离子交换态量有相关性.沉积物中的微生物种类和数量在种植前后有较大变化,种后沉积物中多酚氧化酶和过氧化氢酶活性均有所增加.【期刊名称】《中北大学学报（自然科学版）》【年(卷),期】2010(031)002【总页数】5页(P145-149)【关键词】黑麦草;河道沉积物;重金属;植物修复【作者】李红霞;赵新华;马伟芳【作者单位】天津大学,环境科学与工程学院,天津,300072;天津创业环保集团股份有限公司,天津,300381;天津大学,环境科学与工程学院,天津,300072;天津大学,环境科学与工程学院,天津,300072【正文语种】中文【中图分类】X530 引言随着电镀、化工等工业经济的蓬勃发展,重金属被广泛地使用,作为各类污染物的主要排入场所,城市河道积累了大量污染物,尤其是一些痕量重金属的释放,极大地危害了人类健康.因此,有效去除或修复重金属是当前十分迫切的任务,开发新的污染治理和环境修复技术亦成为当前环境领域的研究热点[1-3].生物修复技术中的植物修复是利用植物及共存的微生物体系有效清除环境中的污染物,是解决受污染河道沉积物中重金属问题的较为经济有效的途径[4-5].本文通过栽培试验研究了种植黑麦草以后,河道污染沉积物中 Ni,Cu,Cd等重金属污染的修复情况,包括黑麦草对沉积物中重金属的吸收和去除,沉积物中微生物的种类和数量的变化,沉积物中酶活性的变化等.1 材料和方法1.1 材料沉积物取自华北某市排污河,其部分基本理化性质如下：阳离子交换量 49.59 cmol(+)◦kg-1;有机质160.4 g◦ kg-1;pH 7.24;全氮50.33 g◦ kg-1;速效磷 65.09 mg◦ kg-1;矿物油 3.86%.重金属总量和不同形态重金属数量见表 1.表1 重金属总量和不同形态重金属含量Tab.1 Heav y metals concentration and different forms in dredg ed sewage river sediment(mg◦kg-1)重金属不同形态离子交换态碳酸盐结合态铁锰结合态有机结合态残渣态总量Ni 8.512 51.092 61.974 50.751 16.714 189.043 Cu 4.208 0.313 1.0185 9.942 396.301 461.782 Cd - - - - 5.796 5.796注：-表示未检测出将过 2 mm筛的沉积物(风干土)混和均匀后装箱,每箱装 75 kg,栽培装置为长方形PVC箱(尺寸为0.6 m× 0.5 m× 0.4 m),底部设通气孔;将箱中沉积物用去离子水调至 50%～ 60% 持水率(W HC),温室栽培,2 d后将黑麦草种子播入,生长一周后间苗,每箱 60株,种植约 60 d(5月 31日～7月 31日)后收获,沿土面剪取地上部分,并挖出根部,分别用去离子水洗净,在105℃下杀青 0.5 h,80℃烘干 2 h,称地上部和根的干重,每个实验设 3个重复,加一个对照.1.2 方法1.2.1 理化性质测定各项理化性质的测定方法参照土壤理化分析[6].1.2.2 重金属总量测定称取 0.2000～ 0.5000 g沉积物样品置于 50 m L聚四氟乙烯坩埚中,用水润湿后加入 10 mL盐酸(d=1.19 g/mL),在通风橱内电热板上低温加热,使沉积物初步分解,待蒸发至约 3 m L时取下稍冷;加入 5 mL硝酸(d=1.42 g/mL),5 mL氢氟酸(d=1.49 g/mL),3 mL高氯酸(d=1.68 g/mL),加盖后电热板上中温加热,定时搅拌防止沸腾,加热至冒浓厚白烟,待坩埚内壁黑色沉积物分解至样品呈粘稠状时,取下稍冷;用蒸馏水冲洗坩埚盖和内壁,并加入 1 mL硝酸溶液,温热溶解残渣,将样品转移至50 m L容量瓶中,加入 5 mL硝酸镧溶液(质量分数为 5%),冷却后定容至 50 mL,摇匀备测.1.2.3 植物中重金属测定称取植物样品约 0.3000 g置于 100 mL聚四氟乙烯坩埚中,加入 10 mL逆王水,冷消化一天,然后热消化,使溶液接近 3 mL;再加入 5 mL HClO4(d=1.68 g/mL),冒白烟后加入适量 HNO3(d=1.42 g/mL),蒸馏水定容至 25 mL,摇匀备测.1.2.4 重金属各形态测定采用 Tessier[7]法测定重金属的 5种不同形态：可交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态.1.2.5 重金属元素的仪器测定采用电感偶合等离子体原子发射光谱仪(日本岛津公司).2 结果与讨论2.1 植物对重金属的吸收图1是黑麦草不同部位累积的重金属数量.表 2是种植黑麦草后沉积物中重金属总量和不同形态重金属的含量.表2 种植黑麦草以后(含对照)沉积物中重金属总量和不同形态重金属含量Tab.2 Heav y metals concentration and different forms in dredg ed sewage river sediment after planting(mg◦kg-1)重金属不同形态离子交换态碳酸盐结合态铁锰结合态有机结合态残渣态Ni 75.912± 1.106 8.044± 0.214 42.683± 0.574 37.944± 0.242 24.460± 1.572 Ni对照29.041± 0.104 34.165± 0.216 59.216± 0.402 47.011± 1.003 39.61± 0.95 Cu 38.23± 0.87 0.07± 0.01 0.63± 0.023 30.88± 0.13 391.972± 1.012 Cu对照9.524± 0.102 0.294± 0.009 0.994± 0.007 54.119± 0.305 396.851± 0.814 Cd - - - - -Cd对照1.207± 0.125 - - - 4.589± 0.119注：-表示未检出黑麦草体内各部位吸收和累积的重金属种类和数量不同,重金属在植物体内各部位的分布情况也有差异.植物积累的重金属被植物根部吸收后运送至地上,其运送能力与多种因素有关,且累积过程与多种防御机制有关[8],植物从土壤中累积的重金属优先贮存在叶表皮细胞中.由图 1可知,黑麦草地上部分积累的重金属Ni,Cu和 Cd量均小于地下部分,其中Ni 地上部分为63.014 mg◦ kg-1,为沉积物中总量的 1/3;Cu地上部分为92.356 mg◦ kg-1,约占 Cu总量的1/5;Cd地上部分为1.449 mg◦ kg-1,占 Cd总量的 1/4.各处理之间无显著性差异(P＞0.05).由表 2可以看出,重金属总量在种植植物前后没有改变,但不同形态重金属数量产生了较大变化,可交换态的迁移性最强,毒性也最强;种植黑麦草以后,离子交换态的 Ni含量由种植前的8.512 mg◦kg-1变为75.912 mg◦ kg-1,主要是因为碳酸盐结合态不稳定,易受 pH值变化的影响,在酸性条件下会向可交换态转化. 的碳酸盐结合态和铁锰结合态在种植之前含量较少,铁锰氧化物结合态和有机结合态都比较稳定,但在一定氧化还原电位和 pH值条件下也会缓慢向可交换态转化;种植黑麦草以后,Cu的两种结合态的含量有所增加,种植之后检测到少量以离子交换态形式存在的 Cd.残渣态在环境中极为稳定,一般不具有毒性和危害. 图1 黑麦草不同部位累积的重金属数量Fig.1 Amount of heavy metals accumulated in different parts of Lolium multiflorum Lam2.2 根际微生物的变化植物根际是根系影响下的一种特殊生态环境,直接影响着根际微生物的种类和数量,为微生物提供营养物质,根际微生物数量比非根际多[9].黑麦草根际的细菌为1.5×106个 /g,比非根际的细菌数低 2个数量级,但都比种植前高 2个数量级;种植后根际真菌为5.4×105个 /g,比根际低 2个数量级,比种植前高出2个数量级.根系分泌物包含的有机酸可以降低根际沉积物的 pH值,使碳酸盐态的重金属转化为生物有效性强的离子交换态或水溶态,促进了重金属在植物体内的累积.实验 15 d后,根际微生物主要是细菌、真菌、藻类等低等生物,根系微生物对重金属的活化提高了重金属的生物有效性,对重金属表现出较高的耐性,有利于重金属向植物体内转移.实验进行 45 d后,黑麦草根际出现了大量丝状菌及其和细菌、真菌的团聚体,它们通过吸附转移、离子交换等累积机制将重金属颗粒累积至植物体内,并通过吸收根际分泌物中的有效成分,与重金属离子络合解毒[10].2.3 酶活性的变化酶是土壤中一切生物过程的重要参与者,其来源于动植物及其残体以及微生物的分泌物;酶活性是生态系统物质循环和能量流动过程中最活跃的生物活性物质,它表征了土壤中物质代谢的旺盛程度;土壤酶活性是土壤生产力和土壤环境质量的重要评价指标[11].测定酶活性有助于判断土壤中重金属污染的程度以及对植物生长的影响.图2为沉积物中多酚氧化酶和过氧化氢酶的活性随着黑麦草生长的动态变化曲线.由图 2可知,多酚氧化酶活性随着时间的推移整体呈现较稳定的线性变化趋势,种植黑麦草之前沉积物中多酚氧化酶活性很低,由于部分有机物得到转化,酶活性的上升速度较快,20 d以后曲线上升幅度增加,30～ 40 d之间变化趋势有所减弱,60 d时呈现最大值,约为 0.10 mg/g土.多酚氧化酶可以将土壤中的多元酚氧化为醌,促进土壤的腐殖化进程.种植黑麦草前过氧化氢酶的活性为 4.85 mL/g土;0～20 d之间基本处于平稳状态,变化幅度不超过 1.00 mL/g土;20 d以后多酚氧化酶活性开始上升,并保持较稳定的上升趋势,60 d时达到最大,为 9.78 mL/g土.过氧化氢酶活性与土壤有机质含量和微生物数量有关,它既参与生物呼吸代谢,又可以分解代谢产生的对生物体有毒害作用的过氧化氢.黑麦草生物量的增加及其根际分泌物、微生物等的共同活化作用,加快了黑麦草修复受污染沉积物中重金属等污染物的进程.图2 酶活性的动态变化Fig.2 Variations of enzyme activity3 结论1)黑麦草对沉积物中不同重金属均有累积效应,植物体内积累的重金属数量与离子交换态的重金属数量有直接关系.2)根际微生物数量在种植黑麦草前后变化较大.实验前期主要是一些低等微生物,实验后期观察到一些较高等级的生物.3)沉积物中多酚氧化酶活性和过氧化氢酶活性均有增加.参考文献：[1]周启星.污染土壤修复的技术再造与展望[J].环境污染治理技术与设备,2002,3(8)：36-40.Zhou Qixing.Technological reforger and prospect of contaminated soil remediation[J].Technique and Equipment for Environmental Pollution Control,2002,3(8)：36-40.(in Chinese)[2]Salt D E,Blaylock M,Kumar P B A N,et al.Phytoremediation：a novelstrategy for the removal of toxic metals from the environment usingplant[J].Biotechnology,1995,13：468-474.[3]骆永明,滕应,过园.土壤修复-新兴的土壤科学分支学科 [J].土壤,2005,37(3)：230-235.Luo Yongming,Teng Ying,Guo Yuan.Remediation-a new branch discipline of soil science[J].Soils,2005,37(3)：230-235.(in Chinese)[4]张太平,潘伟斌.根际环境与土壤污染的植物修复研究进展[J].生态环境,2003,12(1)：76-80.Zhang Taiping,Pan Weibin.Progress in the research of rhizosphere and phytoremediation of contaminated soils[J].Ecology and Environment,2003,12(1)：76-80.(in Chinese)[5]张蕾,李红霞,马伟芳,等.黑麦草对复合污染河道疏浚底泥修复的研究[J].农业环境科学学报,2006,25(1)：107-112.Zhang Lei,Li Hongxia,Ma Weifang,etal.Phytoremediation of complex contaminations in dredged sewage river sediment by lolium multiflorum lam[J].Journal of Agro-Environment Science,2006,25(1)：107-112.(in Chinese)[6]中国土壤学会.土壤农业化学分析方法 [M].北京：中国农业科技出版社,2000.[7]Tessier A.Campbell P G C,Bisson M.Sequential extraction procedure for the speciation of trace metals[J].Anal.Chem.,1979,51：844-851.[8]Jan Mertens,Pieter Vervaeke,An De Schrijver,et al.Metal uptake by young trees from dredged brackish sediment：Limitations and possibilities for phytoextraction and phytostabilisation[J].Science of the Total Environment,2004,326：209-215.[9]何章莉,潘伟斌.受污染土壤环境的植物修复技术[J].广东工业大学学报,2004,21(1)：56-62.He Zhangli,Pan Weibin.Phytoremediation to contaminated soil[J].Journal of Guangdong University ofTechnology,2004,21(1)：56-62.(in Chinese)[10]杨晔,陈英旭,孙振世.重金属胁迫下根际效应的研究进展[J].农业环境保护,2001,20(1)：55-58.Yang Ye,Chen Yingxu,Sun Zhenshi.Progress on effects of heavy metal pollution in rhizosphere[J].Agro-Environmental Protection,2001,20(1)：55-58.(in Chinese)[11]Burns R G,Dick R P.Enzymes in the Environment： Ecology,Activity and Applications[M].New York：Marcel Dekker,Inc.,2001.。

重金属的植物修复

重金属的植物修复摘要本文综述了重金属植物修复的基本机理、目前的进展和展望。

目前植物修复重金属主要包括了植物提取、植物挥发、植物固化和根系过滤等几种技术，通过在植物体吸收转化、与植物体内物质络合和转化为挥发性物质进入大气等机理减轻重金属的污染程度。

重金属种类及其形态、温度、pH 和根系微生物等因素都会影响植物修复的效率。

植物修复与传统的修复技术相比，具有很大的优越性，但同时也有其局限性。

关键词：重金属污染，植物修复，超积累植物引言随着工业的发展，土壤和水域的重金属污染已成为全球一个严峻的问题。

据统计，我国约有3万多hm2土地受汞的污染，有1万多hm2土地受镉的污染，每年仅生产“镉米”就达5万t以上，而每年因污染而损失的粮食约1200万t⑴。

重金属污染具有稳定性高、不可逆和后果严重等特点至今没有找到理想的治理方法，而传统的工程、物理和化学等手段因耗资大、易产生二次污染等原因限制了其在修复重金属上的应用，因此需要探索在不破坏生态环境的情况下治理重金属污染的新途径 1 2。

植物修复(Phytoremediation )是利用绿色植物来转移、容纳或转化土壤或水体中的污染物使其对环境无害3。

植物修复的对象是重金属、有机物或放射性元素污染的土壤及水体。

植物修复是一种很有潜力、正在发展的清除环境污染的绿色技术,也是一门正在崛起并涉及土壤学、植物学、分子生物学、基因工程学、环境工程等多门学科的新兴边缘学科。

它具有成本低、不破坏土壤和河流生态环境、不引起二次污染等优点。

自20 世纪90 年代以来,植物修复成为环境污染治理研究领域的一个前沿性课题4。

植物固化指的是利用植物根际的一些特殊物质使土壤中污染物转化为相对无害物质的一种方法，从而减少其对环境和人类健康的风险。

在这过程中土壤重金属的含量并不减少，只是暂时将其固定，其中包括分解、螯合、氧化还原等多种过程。

Salt D. E.等人在1995通过实验证明植物能将六价铬转变为三价铬，从而减小了伤害性。

Phytoremediation

Case study
- A liquid fertilizer was supplied weekly to the plants - grow time 4 weeks - Adding selected soil amendments - Plants were harvested 1 week after adding amendments - Shoots were washed - Were dried in an oven at 70°C - Analyzed for U by ICP-AES
Case study
Desorption to soil solution
200 fold increase from 1.2 to 240 mg pH was reduced by 0.5 to 1 unit
Case study
Case study
Case study: Results
- B. juncea is the best plant to accumulate U -Citric acid is the best acid to increase the U uptake of plants -U accumulation is associated with a stronger Pb accumulation -Even in one species there are differences in U uptake -For remediation, the soil has to be washed first with acid to desorp from soil particles - Hyperaccumulation is rapid

超富集植物叶用红菾菜( Beta vulgaris var.cicla L.)及其对Cd的富集特征

农业环境科学学报２０ｃｒ７，２６（４）：１３８缸１３明Ｊ０啪ａＩｏｆＡ驴Ｅｌｌｌ，ｉＩ删匝即ｌｓｃｉｅｎ∞超富集植物叶用红慕菜及其对Ｃｄ的富集特征（晚尬钐Ｍ枷函秒矾ｃＺｅｋＬ．）李玉双，孙丽娜，孙铁珩，王洪（沈阳大学沈阳环境工程重点实验室，辽宁沈阳１１００４４）摘要：超富集植物是重金属污染土壤植物提取修复的基础．超富集植物的筛选一直都是污染土壤植物修复研究的热点及前沿。

采用盆栽实验对７种农作物积累Ｃｄ的特征进行研究，结果表明，叶用红恭菜对Ｃｄ具有较高的富集系数和转移系数。

在此基础上，采用盆栽浓度梯度试验对叶用红恭菜对Ｃｄ的富集潜力及富集特征进行了系统研究。

结果表明，在Ｃｄ污染水平为２０ｚｎｇ·ｋｇ。

１条件下，叶用红恭菜地上部ｃｄ含量超过了１００ｍｇ·ｋ一这一国际公认的Ｃｄ超积累植物应达到的临界含量标准；且其对Ｃｄ的富集系数和转移系数均大于ｌ；同时，与对照相比，植物的生长未受到抑制，这表明叶用红恭菜是一种Ｃｄ超积累植物，为Ｃｄ污染土壤的植物修复提供了一种新的种质资源。

关键词：叶用红恭菜；植物提取修复；镉；超富集植物中图分类号：ｘ１７２，Ｘ５３文献标识码：Ａ文章编号：１６７２－２０４３（２（忉）０４－１３８６－０４Ｃａｄ眦眦Ｉｂ睥瑚ｃ咖ｍａｔ盯助砌ｌ，Ｈ咖廊＇憾＾ｃ幻缸Ｌ．舳ｄｌｔｓＡｃ伽岫ｔｉｌ嗜ａ嘲嗡ｃｔ时ｉ娟娼ＵＹｕ喝ｈｕ锄ｇ，ＳＵＮⅡ－ｎａ＇ＳＵＮＴｉｅ－ｈｅＩｌｇ，ＷＡＮＧＨｏｎｇ（ｓｈｅｎｙ蚰ｇｌ（ｅｙｂｂ哪ｔｏｒ）ｒｏｆＥｎｖｉＭ册ｅｎｔａｌＥｎｇｉＩｌｅ硝ｎｇ，ＳｈｅｎｙａＩｌｇＵｌｌｉｖｅ瑙ｉｔｙ，ｓｈｅｎｙ蚰ｇ１１００４Ｊ４，Ｃ垴豫）Ａｈｔｍｃｔ：ＨｙｐｅｍｃｃｕｍＩｌｌａｔｏ玛ａ他ｍｅｂ鹊ｅ０ｆｐｈｙｔｏｅｘｍ帕ｔｉｏｎ．ｎｉｓｄ逾ｉｃｕＩｔｔｏｓｃ他邮蛐ｔｉｄｅａｌｈｙｐ啊∞ｃ岫ｌｌｌａｔｏ玛ｔｈ砒ｃ蛐ｍｍｅｄｉａｔｅｓｏｉｌｃ伽ｔａＩＩＩｉｎｇｔｅｄｗｉｍｈｅａｖｙｍｅｔａｌ８ｅ雎ｃｔｉｖｅｌｙ．Ａｐｏｔｅｘｐｅｒｉｍ即ｔｗ∞ｃ∞ｄｕｃｔｅｄｔ０ｉｎｖｅ８ｔｉｇ砒ｅｔｌｌｅｃｈ啪ｃｔｅｒｉ８ｔｉｃｓｏｆ∞ｃ岫蝴ｎｇＣｄｂｙｃｒ叩８．，Ｉｋｒｅｓｕｌ协８ｈ０Ｗｅｄ山ａｔＣｄｉｎ８ｈ∞ｔｏｆ＆缸口Ｈ冶硎ｓ伽ｒ．ｃ记缸Ｌｗ舶ｔｌｌｅｌＩｉ咖ｅｓｔ枷∞ｇａｌｌｐｈＩｌ协，舳ｄＣｄｃｏｎｃｅｎ嘣ｉ帆ｉｎｓｈｏｏｔｏｆ＆船分“细嘛口矾ｃ记如Ｌｗ鹊ｈｉｇＩｌｅｒｔｌｌ明ｔｌｌａｌｉＩｌ瑚ｔ．ＡｎｏｔｌＩｅｒｐｏｔｅｘｐｅＩｉｍ髓ｔｗ羽锄ｎｇｅｄｗｉｍｖａｒｉｏｕ８Ｃｄｃ∞ｃｅｎｔｌ丽ｏｎ８ｔｏＢｔＩｌｄｙＣｄ∽ｃｕｎｍｈ＿ｔｉ册，ｔｏｌｅ砌ｃｅｏｆ＆船口以ｇ喇ｓ口矾ｃ如缸Ｌ蚰ｄｉｔ８ｐｏｔｅＩｌｔｉａｌｆｏｒｐｈｙｔ０怫ｍｅｄｉ鲥ｏｎ．弧ｅａＶｅ豫ｇｅｃｏｎｃｅｎ咖ｏｎｏｆＣｄｉｎｓｈｏｏ协０ｆ＆组口ｕ２奢咖口矾ｃ幻如Ｌ．缸ｅａｔｅｄ访ｔｌｌ２０ｍｇ·ｋｇ－１（Ｃｄ）ｗ鹊ｍｏｒｅｔｌｌ肌ｔｌｌｅ∞ｃｅｐｔｅｄｃ觚ｃａｌｃｏｎｃｅｎ打ａｔｉ彻ｏｆ１００ｎｌｇ·ｋｇ一．７ｎ屺Ｃｄｅ嘶ｃｌｌｍｅｎｔｃｏｅｆｆｉｃｉｅｎｔ圆ｃ）肌ｄ饥ｍ８ｌｏｃａｔｉ鲫ｆａｃｔｏｒ（ＴＤｏｆ＆缸口“４卿ｓ口矾ｃ如如Ｌｗｅ陀ｈｉｇｈｅｒｔｌＩ锄１．Ｍｏｒ∞ｖｅｒ，ｃｏｍｐａｒｅｄｗｉｔｌｌｍｅｃｏｎｎＤＩ，ｔｈｅ伊州ｍｏｆ点醣地口“扛ｇＨ凡伽ｎｃ幻陆Ｌ．ｉｎｔｌｌｅｈ℃咖ｅｍｏｆ２０ｍｇ．ｋｇ一１（Ｃｄ）ｗ鹊ｎｏｔｉｎｈｉｂｉｔｅｄ，∞，点ｋ纽口叫ｇ捌ｊ口仉ｃ记缸Ｌｗ鹊ａ∞ｄ扣血吼ｈｙｐ哪ｃｃｌ】ｍｕｈｔｏｒ肌ｄｃｏｕｌｄｂｅ印ｐｌｉｅｄｔｏｐｈｙｔｏｒｅｍｅｄｉａｔｅ（温一ｃｏｎｔａｌ！Ｉｌｉｎａｔｅｄ舳ｉｌｓ．豳羽ｒｏｒｄｓ：＆缸ｔ，“弛疏ｔＩ戤ｃｆｃ缸Ｌ；ｐｈ皿慨唿ｃ硒ｎ；明ｄｎ衄ｍ；ｈｙ岬ｃ∞珊ｌｌ姗土壤是人类赖以生存的主要自然资源之一．也是人类生态环境的重要组成部分。

砷超富集植物蜈蚣草及其对砷的富集特征(1)

砷超富集植物蜈蚣草及其对砷的富集特征(1)篇一:全世界已发现的重金属超富集植物有5_多种全世界已发现的重金属超富集植物有5_多种,其中360多种是Ni的超富集植物.韦朝阳,陈同斌等[_]通过野外调查和栽培实验,发现了砷超富集植物蜈蚣草.其叶片含As可达5_0 mg/kg,在含砷9 mg/kg的正常土壤中,蜈蚣草地下部和地上部对砷的生物富集系数分别高达71和80.韦朝阳等[_]发现了另一种As的超富集植物大叶井口边草,其地上部分平均含As量为4_ mg/kg,最大含As量可达694 mg/kg,生物富集系数为1.3～4.8.杨肖娥.龙新宪等[_]发现了一种新的Zn的超富集植物东南景天,天然条件下东南景天的地上部分Zn平均含量为45_ mg/kg.营养液培养试验表明,其地上部分含量最高值可达_674 mg/kg.李华和姜理英[_]等研究了耐性植物海洲香薷对Cu的吸收和积累,指出虽然地上部分Cu积累水平未达到超富集植物的要求,但由于其生物量大,根系能超富集Cu,植株Cu总积累较高,可考虑将其用于Cu污染土壤的植物修复.李红艳等[_]报道菊科植物艾蒿和滨蒿对Cu也表现出高的富集能力,其中艾蒿地上部分的Cu 含量为91-698 mg/kg,滨蒿为42～259 mg/kg.范稚莲,莫良玉[_]在对典型矿区进行调查后发现,生长在锰矿区的狗牙根,香附子和菜蕨中Mn的含量分别达到275_,__4和_5_ mg/kg,相应的富集系数为_.4,6.7和4.8.这3种植物均达到Mn 超富集植物的相关标准,是潜在的Mn超富集植物.柯文山等在温室砂培盆栽条件下对十字花科芸薹属5种植物芥菜,芥兰,鲁白,竹芥,甘蓝进行铅吸收和耐性的研究,认为鲁白,芥菜不仅生长快,生物量高,且其地上铅的含量超过1_0 mg/kg,迁移总量和迁移率都很高,是很好的潜在修复铅污染的材料.近期对Pb富集植物品种的筛选的研究还有,聂俊华等对生长于铅锌尾矿区的36种植物进行了筛选,以叶片叶绿素含量,株高,植株含Pb量为Pb富集植物的筛选指标进行实验筛选.筛选出6个富集Pb的植物品种,分别是香根草.绿叶苋菜,裂叶荆芥,羽叶鬼针草,紫穗槐和苍耳.吴双桃等人首次报道了土荆芥是一种铅超富集植物,其茎叶Pb质量分数高达3888 mg/kg.杨远祥在四川汉源县普陀山铅锌矿区筛选到了铅和锌的超富集之物小鳞苔草,其地上部分锌最大积累量91.85 mg/kg,铅最大积累量1_3.23 mg/kg;铅,锌转运系数分别为1.961和0.996.铅,锌胁迫处理发现,小鳞苔草根部和地上部分对铅含量最高分别可达_95.96 mg/kg和_34._ mg/kg,对锌含量最高分别可达483.93 mg/kg和4_.23 mg/kg;植株对铅富集系数最高可达3.1,对锌则富集系数最高可达4.76.篇二:环境工程湖南省重金属污染及其修复摘要:最近二十年,随着经济列车的不断加速,我国进入了环境高风险时期,各种环境污染事件层出不穷,尤其是最近十年,环境污染事件的发展规模.损害后果.污染类型等都日趋扩大.这里搜集整理了湖南省_年至_年最近十年的重大重金属环境污染事件,并在综合评价湖南省主要有色金属矿区土壤重金属污染现状的基础上,通过对矿区周边优势植物物种进行现场实地筛选和研究,论述了利用累积和超累积植物修复矿区重金属樗染土壤的可行性．从而为矿区土壤重金属樗染治理.土地复垦和生态植被恢复提供了科学依据,也希望能以这些沉重的纪录,打捞那些并不遥远的惨痛记忆,催生起共同保护家园的意识和行动. 关键字:重金属污染事件后果植物修复一.有色金属矿区重金属污染对周边生态环境的破坏效应湖南省有色金属矿藏十分丰富,素有〝有色金属之乡〞之称．迄今为止,在湖南境内已发现有色金属(含贵金属)矿产_种,已探明有色金属矿床340多处【1】.有色金属矿产的大规模开发一方面给湖南省带来巨大经济效益,另一方面又加重了对矿区周围生态环境的污染和破坏．有色金属矿由于品位低.提取工艺复杂,固体废弃物产量大,破坏和压占了大量土地．多年积累下来,面I临的土地复垦与生态恢复问题十分严重．有色金属矿产的开采会导致大量尾矿的产生．据统计,平均每开采l t矿石将产生O．92 t尾矿砂,其中包含的高浓度重金属对绝大多数植物的生长发育都将产生严重抑制和毒害作用．矿区周边地区的生态环境破坏几乎都是直接或间接的由矿山开采所排放的大量酸性矿井水和尾矿砂中所包含的高浓度重金属造成的,其中尤以土壤重金属污染危害最大．土壤重金属污染主要通过以下途径对环境产生危害:(1)土壤中的重金属通过雨水淋溶作用向下渗透,可能导致地下水的污染．(2)受污染的土壤直接暴露在环境中,通过土壤颗粒物等形式直接或间接地为人或动物所吸收．(3)外界环境条件的变化如酸雨.施加某些土壤添加剂等因素提高了土壤中重金属的生物可利用性,使得重金属较容易为植物吸收利用而进入食物链,对食物链级上的生物产生毒害．(4)有毒重金属进人土壤后不易分解而转化或富集,所以它所产生的污染过程具有隐蔽性,长期性和不可逆性的特点,对环境和生物的潜在危害极大．在湖南省境内土壤重金属污染表现为以Pb.Zn 2种重金属为主,同时伴生着Cd.Cu.As 3种重金属复合污染为主要特征,极大地增加了重金属污染土壤治理和土地复垦的难度．二.污染事件（一）湖南岳阳砷污染事件_年9月8日,湖南省岳阳县城饮用水源地新墙河发生水污染事件,砷超标_倍左右,8万居民的饮用水安全受到威胁.经调查,造成此次污染的祸首是上游3家化工厂,因日常性排放工业污水,致使大量高浓度含砷废水流入新墙河【2】.（二）湖南浏阳镉污染事件_年,湖南省浏阳市镇头镇双桥村通过招商引资引进长沙湘和化工厂,次年4月,该厂未经审批建设了1条炼铟生产线,并长期排放工业废物,在周边形成了大面积的镉污染,进而导致植被大片枯死,部分村民因体内镉超标出现头晕.胸闷.关节疼痛等症状,两名村民因此死亡._年7月29日.30日,当地上千名村民因不堪污染之害,围堵镇政府.派出所.事后,与制造污染有关的企业负责人.政府官员等受到刑事追究.停职等处理【2】.（三）〝有色金属之乡〞饮水告急_年有调查报告披露,被称为〝有色金属之乡〞的湖南,采选.冶炼.化工等企业多分布于湘江流域,由此导致了严重的重金属污染.多年以来,湖南的汞.镉.铬.铅排放量位居全国第一位,砷.二氧化硫和化学耗氧量(COD)的排放量居全国前列.湘江流域鱼类大幅减少,数以千亩的农田无法耕种,相当地域的鱼类.粮食.蔬菜不能食用,4_0万人口的饮用水安全受到威胁【2】.三.湖南省境内累积和超累积植物的调查.筛选及可行性分析（一）重金属污染土壤的植物修复技术植物修复技术是以植物忍耐和超量积累某种或某些化学元索的理论为基础,利用植物及其共存微生物体系清除环境中的污染物的一门环境污染治理技术,它是一门新兴起的应用技术,已被当今世界迅速而广泛接受,正在全球应用和发展【3】.该项技术根据其作用过程和机理可分为植物提取.植物挥发(PhytoV0latilization).植物稳定或固化.植物根系过滤等．与传统方法相比,植物修复具有治理效果的永久性.治理过程的原位性.治理成本的低廉性.环境美学的兼容性.后期处理的简易性等优点,在一定程度上弥补了传统修复方法的不足.（二）湖南省境内具有修复潜力植物物种的筛选利用植物吸收并通过收割以去除重金属元素,是治理土壤中这类污染物的根本途径．不管是植物提取.挥发还是植物稳定.植物根滤作用,植物本身的特性是决定污染治理效率的关键．因而,累积.超累积植物对于土壤金属污染修复具有异乎寻常的意义.,通过对湖南省部分有色金属矿区周边优势植物物种的筛选和其对重金属复合及单一污染抗性的研究,取得了一些突破性研究成果:现已在湖南省某铅锌矿区发现雀稗.双穗雀稗.黄花穗.银合欢4个优势种植物能够成功地在铅锌尾矿上定居.．另外,在超累积植物的发掘方面也取得了一些进展,例如薛生国等人在湖南省发现了一种锰超累积植物——商陆【4】;陈同斌等在湖南常德发现了超富集砷的风尾蕨植物——蜈蚣草【5】;中科院韦朝阳等人在湖南发现砷超累积植物——大叶井口边草【6】;湖南农业大学曾清如等人在湖南郴州东坡铅锌尾矿砂的严重污染区发现并种植了对重金属有明显抗性的杨树【7】.（三）.可行性分析利用累积或超累积植物修复矿区重金属污染土壤具有物理.化学和其他生物修复方法无可比拟的优势．具体表现在以下几个方面:(1)利用植物的吸收.富集.提取和挥发可以永久地解决土壤重金属污染问题．(2)修复植物的稳定作用可以绿化污染土壤,使地表稳定,防止污染土壤因风蚀或水土流失而带来的污染扩散问题．(3)可以尽可能减少由于土壤清洁造成的场地破坏,对环境扰动少,减少来自公众的关注和担心．(4)经植物修复过的土壤,其有机质含量和土壤肥力都会增加,一般适用于农作物种植,符合可持续发展战略．(5)修复植物的蒸腾作用可以防止污染物质对地下水的二次污染．(6)重金属超累积植物所累积的重金属在技术成熟时可进行回收,从而也能创造一些经济效益．(7)植物修复的过程也是绿化环境的过程,易被社会所接受．(8)植物修复成本低,可以在大面积污染土壤上使用．植物修复的以上众多优点证明了利用超累积植物修复重金属污染土壤在实际应用中的可行性.尽管利用植物修复和复垦矿区污染土壤存在众多优势并具有实践可行性,然而目前仍然存在一些技术上的难点.这些难点仍需要做进一步的研究.四.讨论利用累积或超累积植物修复有色金属矿区重金属污染的土壤,无论从技术上还是从实践应用方面都是切实可行的,尽管目前这种技术还不十分成熟和完善,然而其以其它修复方法无可比拟的优势逐渐引起了人们的重视,成为了当今国内外学术界相关领域研究的热点．目前在湖南省用累积或超累积植物治理和复垦重金属污染土壤虽然还主要集中在试验和尝试性阶段,但不乏也有一些成功的工程应用实例．例如王凯荣等人在湖南安化镉污染严重的铀矿区调整农田种植制度,建立新的生产经营模式,应用种桑养蚕.种植纤维作物,达到了镉污染土地的安全高效利用,农民.政府.矿区三满意的效果【8】 ;曾清如等人在湖南郴州东坡铅锌尾矿砂的严重污染区种植对重金属有明显抗性的杨树,利用该种树生长快.富集土壤中的重金属和净化土壤的特点,不仅美化了环境,净化了土壤,且利用该树材质来生产火柴,可产生明显的经济效益等【7】.在对矿业废弃地复垦中, 不但要求在废弃地上重新种上植物,而且还要使废弃地可以重新利用来进行农业生产．这就需要逐渐将基质中的重金属浓度减少到可接受的水平,这时候累积或超累积植物就可以极大地发挥其富集高浓度重金属的修复潜力了．为了在有毒金属矿区的土地上建立一个可自我维持的植被,可以先选择一些能够同时耐受特定金属.干早和低营养水平胁迫的先锋植物．在这些耐性先锋种生长过一段时间或经一定程度修复后的金属污染地上种累积或超累积植物将更有助于把重金属从污染地中清除.加快矿区土地的复垦.生态植被恢复和减少地下水的污染,从而将重金属对环境和生物的危害减小到最低限度.五.结束语人们为了眼前的利益,大量的开采矿产,从而对矿区周围的居民.生物及环境造成了严重危害.现在国家.政府以及一部分人已经意识到环境污染的严重后果,环境保护的重要性.国家.人们正采取一些措施对重金属污染的地区以及其他污染地区进行修复,并提倡以后要走经济稳定发展.保护环境的可持续发展道路.参考文献【1】谢炳庚,李晓青．湖南有色金属矿产资源及其地域开发研究[J]．经济地理．_96,_(4):79—82.【2】民主与法制周刊,近年来重大环境污染事件记录,环保资讯,_-_-_.【3】Salt D E．Blaylock M,Kumar N P B A,et a1．PhytoremediationIa novel strategy for the removal of to_icetals from the environment using plant [J]．Bio—technology．_95,_:468～474.【4】薛生国．中国首次发现的锰超积累植物一商陆[J]．生态学报．_t23(5);935—937.【5】陈同斌,韦朝阳,黄泽春,等．砷超富集植物蜈蚣草及其对砷的富集特征 [J]．科学通报,_,47(3);2_—2_.【6】Wei C Y,Chen T B,Huang z C,eta1．Cretan Brake(Pteris cretica L．)j a Arsenic—accumulating Plant[J]．Acta Ecological Sinica,_, _(5):777—778.【7】曾清如,杨仁斌．铁柏清,等,郴县东西河流域重金属污染农田的防治技术和生态利用模式[J]．农业环境保护,_,_(5)z428-432.【8】王凯荣,陈朝明,龚惠群,等．工矿污染农田生态整治与安全高效利用模式研究[J]．中国环境科学,_98,_(3):97-1_.篇三:富集金属的植物与普通植物相比,学术界认为,超富集植物一般应具备4个基本特征:首先,临界含量特征,即植物地上部如茎或叶重金属含量应达到一定的临界含量标准,如锌.锰为_ _0毫克/千克;铅.铜.镍.钴.砷均为1 _0毫克/千克;镉为1_毫克/千克;金为 1毫克/千克. 其次,转移特征,即植物地上部重金属含量大于根部重金属含量. 第三,耐性特征,即植物对重金属具有较强的耐性.其中对于人为控制试验条件下的植物来说,是指试验中与对照相比,植物茎.叶.籽.实等地上部分的干重没有下降.对于在自然污染状态下生长的植物来说,是指植物的生长从长相来看没有表现出明显的毒害症状. 第四,富集系数特征,即植物地上部富集系数（定义:指某种元素或化合物在生物体内的浓度与其在的环境中的浓度的比值）大于1.一般来讲,植物体内重金属含量随土壤中含量的增加而提高.世界上已发现超富集或具有超富集性质的植物多达几百种,涉及十字花科.凤尾蕨科.菊科.景天科.商陆科.堇菜科.禾本科.豆科.大戟科等.在我国,科研人员已经发现了蜈蚣草.东南景天.龙葵.宝山堇菜.商陆.圆锥南芥.李氏禾等砷.锌.镉.锰.铅.铬等超富集植物,转移系数（translocation factor）是地上部元素的含量与地下部同种元素含量的比值,即:转运系数﹦地上部植物中元素含量／地下部植物中元素含量.用来评价植物将重金属从地下向地上的运输和富集能力.转移系数越大,则重金属从根系向地上器官转运能力越强滇白前 .调查,表明其地上部中含Zn.Pb 和Cd 平均为（_ _3±3 537）.（1 546±1 _4）和（391±_6）mg·kg -1 ,富集系数（地上部和土壤金属质量分数之比）分别为 0.35.0._ 和 1._,转运系数（地上部和根中金属质量分数之比）均超过1,均值分别为8._.3.90 和8.36.野外调查数据表明,滇白前是一种Pb/Zn/Cd 共超富集植物.滇白前对Zn. Pb 富集系数小于1,主要是由于其对应土壤中Zn.Pb 质量分数太高（平均分别为（45 778±32 8_）.（_ 5_±_ 6_）mg·kg -1 ）所致.李氏禾李氏禾(Leersia He_andra Swartz)是中国境内发现的第一种铬超富集植物.通过水培实验,评价了李氏禾对水中Cr.Cu.Ni的去除潜力.结果表明,李氏禾能够有效去除水体中的Cr.Cu.Ni污染物,重金属初始浓度分别为_和_ mg·L-1的营养液,_ d 后Cr浓度降低到原子吸收分光光度法检出限以下,_ d后Cu浓度降低到 1._ mg·L-1和1.25 mg·L-1,_ d后Ni浓度降低到1._和2._mg·L-1.收获的植物根.茎.叶中重金属含量均较高,根中重金属含量显著高于茎.叶.单株生物量的比较结果表明,含Cr培养液中生长的李氏禾生物量与对照相比无显著减少(P 0._),含Cu.Ni营养液中生长的李氏禾生物量均显著低于对照(P 0._),表明李氏禾对Cr的耐性强于Cu和Ni.李氏禾适宜于湿生环境中生长,能对多种重金属产生大量富集,对Cr.Cu.Ni等重金属污染水体的修复表现出较强的潜力.宝山堇菜通过野外调查和温室试验,发现并证实宝山堇菜(Viola baoshanensis)是一种Cd超富集植物.自然条件下,宝山堇菜地上部Cd平均含量为_68 mg/kg,变化范围为465～23_ mg/kg;地下部Cd平均含量为981 mg/kg,变化范围为233～_46 mg/kg.地上与地下部Cd含量比值变化范围0.41～2._,平均为1.32.Cd生物富集系数变化范围为0.7～5.2,平均为2.38.营养液培养试验研究表明,宝山堇菜地上部Cd 含量随生长介质中Cd浓度的增加而呈线性增加.营养液Cd浓度为50 mg/L时,地上部Cd平均含量达到4825 mg/kg,在Cd浓度为30 mg/L时,生物量达到最大值;地上与地下部Cd含量的比值变化范围为1._～2._,平均为1.67,显示宝山堇菜不仅可以超量吸收Cd,而且可以从地下向地上部有效输送.宝山堇菜的发现将为Cd超富集植物的生理.生化.遗传和进化及其在Cd污染土壤修复方面的研究提供新的重要材料.圆锥南芥随着Cd添加浓度的增加,圆锥南芥的生物量.叶片数.直径长以及Cd含量均呈增加趋势.Cd添加浓度为240mg kg-1时,生物量增加了_7%,叶片数增加了1._倍,直径较对照增加了_0%,叶片中Cd含量达到451mg kg-1.NO3--N和NH4+-N呈先降低后升高的变化趋势,在Cd浓度为240mg kg-1时,达最大值东南景天形态特征多年生草本;茎基部横卧,着地生根;花茎高１０－２０厘米,有分枝;叶互生,下部叶常脱落,条状楔形.匙形至匙状倒卵形,长１.２－３厘米,顶端钝,有时微缺,基部狭楔形,有距;蝎尾状聚伞花序花多,苞片似叶而小;花无梗,直径１厘米;萼片条状匙形,不等长,基部有距;花瓣黄山;鳞片５,匙状正方形,长１－２毫米,顶端钝截形;心皮５,卵状披针形,直立,基部合生;骨突果斜叉开.环境作用东南景天是近年在浙江衢州.湖南郴州古老的铅锌矿区发现的一种锌.镉.铅超积累植物,能将镉.锌.铅等较多地吸收到植株的地上部,有效减轻土壤重金属污染. 东南景天不仅对土壤过量的锌.镉.铅具有强忍耐能力和超积累特性,并具有多年生.无性繁殖.生物量较大及适于刈割的特点.同时,它适应性强,耐瘠薄.干旱及强光等恶劣生境,观赏性强,是实施植物修复与生态绿化的优良植物.以下列举了一些常见的可作修复重金属元素污染的超富集植物.这种植物具有很强的超富集能力,其叶片含碘量可达千分之八,能够抵受含碘量为 3%的受污染环境.它的富集能力随着生长发育不断增强,超富集特性还可以遗传给下一代.在我国南方的湖南.广西等地大面积存在,其生长旺盛,个体高大. 紫茬苜蓿对铅有很强的富集能力,其根.茎.叶的富集能力依次为根〉茎〉叶,紫茬苜蓿的生物量很高,可大面积种植.芥（gai）菜不仅可吸收铅,也可吸收并积累铬.镉.镍.锌和铜等重金属元素,春天时在野外大面积生长,是一种野生植物.凤眼莲素称水葫芦,是一种浮生植物,每公顷凤眼莲 1 天可从污水中吸收银1.25 千克,吸收金.铅.镍.镉.汞等有毒金属2. _5 千克.除了以上这些植物,一些其它的水生和沼生植物如水浮莲.水风信子.菱角.芦苇和蒲草等都能从污水中吸收金.银.汞等多种总金属元素.地榆达到对Cd.Cu具有超富集能力,其富集系数分别为1.78和1._;苦荬菜对Cd.Zn的富集系数分别为2.76和1.37;白花败酱对Cd和Pb的富集系数分别为1._和1._.种群爆发种群爆发（Population outbreaks ）,是指动物密度比平常显著增加的现象.合适的气候条件和食物条件.天敌控制的解除.种群内部机制等常为爆发的原因.多种农作物害虫.森林害虫都具有突然爆发的特征,一旦发生,如果控制措施跟不上就会形成严重虫灾.像红蜘蛛.蝗虫.松毛虫等都可能经过相当时间低密度期以后,在某一特别有利的时间突然大爆发,造成大面积虫害.大面积单一种植易于引起虫害大爆发.农药的滥用造成天敌减少以后也容易引起害虫大爆发. 植物也有形成严重危害的例如,贯叶金丝桃,多年生有毒杂草,欧亚大陆.__年被带入美国加洲北部,到 _44年,扩展到80万公顷._67年,新疆北部农区小家鼠种群大发生,波及3个专区_多个县,粮食损失达1.5亿kg. 小家鼠有特别强大的生殖潜能,但其潜能的发挥受到其自身种群密度和多种环境因素的制约.种群密度的改变可导致个体极显著的生理变化和行为改变,在高密度的种群中,观察到肾上腺皮质增生,幼体胸腺萎缩和雌雄个体生殖腺的萎缩,表现出繁殖受到强烈的抑制.加上气候.农业收成和疾病的影响,使得小家鼠种群动态十分复杂多变.在个别年份,其数量可猛增千倍左右.如新疆天山北麓于_67年,伊犁谷地于_70年,都曾发生过小家鼠的大暴发,造成极大的危害.小家鼠数量的年间变化幅度也很大,并无一定周期,但并非没有规律.如在高数量年后,一般紧接着一个或几个低数量年,而且前一年数量越高,随后的数量越低,影响越久.根据其数量水平和危害特点,可将小家鼠的数量分为大暴发年.小暴发年.中暴发年和低数量年..（1）数量高各主要栖息地捕获率均超过50%.由于夹日法的固有缺点,不能反映高密度种群的数量,所以其实际密度更高.（2）发生早,持续期长,消退急骤两大暴发年5月份鼠密度很高,6～_月份成群危害,到下第一场雪时则突然消失.（3）行为改变集结流窜,白天也活动,无所不食.（4）危害烈,破坏力特强可以成片毁灭庄稼,咬毁室内各种物品,酿成地区性特大灾害.（5）鼠个体趋小,抗逆性变弱数量中常年份小家鼠平均体重_.2g,每千克58只,大暴发年平均体重不足_g,每千克72只.中常年份雪后小家鼠仍很活跃,在野外也能保持相当数量,大暴发年的头场雪后鼠群骤逝,表明其耐寒性极弱.（6）生理改变生殖腺萎缩,_月上旬即全部停止繁殖,雌成鼠无一怀孕.（7）种群崩溃大暴发后次年种群数量必降至最低点,即种群〝爆炸〞以后出现〝崩溃〞现象. _57年,索马里蝗灾,蝗虫约_0亿只,总重5万吨. _-_年,锡盟发生蝗灾,造成严重损失蝗虫属直翅目,昆虫纲.蝗科.虫体一般绿色或黄褐色.咀嚼式口器.后足大,适于跳跃.不完全变态,幼虫称为〝蝻〞,主要以禾本科植物为食.蝗虫种类很多,世界上共有1万余种,我国有3_余种,如飞蝗.稻蝗.竹蝗,意大利蝗.蔗蝗.棉蝗等.蝗虫是农林业的主要害虫.人类很早就注意到严重的蝗灾往往和严重旱灾相伴而生.我国古书上就有〝旱极而蝗〞的记载.近几年来非洲几次大蝗灾也都与当地的严重干旱相联系.造成这一现象的主要原因是,蝗虫是一种喜欢温暖干燥的昆虫,干旱的环境对它们繁殖.生长发育和存活有许多益处.因为蝗虫将卵产在土壤中,土壤比较坚实,含水量在_%～_%时最适合它们产卵.。

环境工程英语翻译原文

Evaluation of the eﬀect of small organic acids on phytoextraction of Cu and Pb from soilwith tobacco Nicotiana tabacumMichael W.H.Evangelou *,Mathias Ebel,Andreas SchaeﬀerInstitut fu ¨r Biologie V,RWTH Aachen,Worringerweg 1,52056Aachen,Germany Received 1February 2005;received in revised form 23August 2005;accepted 24August 2005Available online 6December 2005AbstractPhytoremediation,the use of plants to extract contaminants from soils and groundwater,is a promising approach for cleaning up soils contaminated with heavy metals.However its use is limited by the time required for plant growth,the nutrient supply and,moreover,by the limited metal uptake capacity.Synthetic chelators have shown positive eﬀects in enhancing heavy metal extraction,but they have also revealed several negative side-eﬀects.The objective of this study was to investigate the use of three natural low molecular weight organic acids (NLMWOA)(citric,oxalic,and tartaric acid)as an alternative to synthetic chelators.Slurry-,column-,toxicity-and phytoextraction experiments were per-formed.For the phytoextraction experiment the three NLMWOA were applied to a copper-and a lead-contaminated soil respectively.A signiﬁcant increase in copper uptake was visible only in the citric acid treatment (67mg kg À1)in comparison to the EDTA treatment (42mg kg À1).The NLMWOA application showed no enhanced eﬀect concerning the lead phytoextraction.A possible explanation for this lack of signiﬁcance could be the rate of the degradation of NLMWOA.This rate might well be too high for these heavy metals with low mobility and bioavailability such as lead.The amounts of NLMWOA applied to the soil were very high (62.5mmol kg À1of soil)and the eﬀect was too little.In this respect EDTA,which was applied in very small amounts (0.125mmol kg À1)was more eﬃcient.Thus making NLMWOA unsuitable to enhance phytoextraction of heavy metals from soil.Ó2005Elsevier Ltd.All rights reserved.Keywords:Phytoremediation;Heavy metals;Organic acids;Chelate assisted;Tobacco1.IntroductionPhytoremediation is deﬁned as the use of green plants in removing pollutants from the environment,or render-ing them harmless (Raskin et al.,1997).Phytoremedia-tion can be used to remove organic as well as inorganic pollutants.As compared to other remediation technologies,such as land ﬁlling,ﬁxation and leaching,it is cost-eﬀective,and as it does not adversely alter the soil matrix;it causes only minimal environmental distur-bance.The sites are usually aesthetically pleasing and therefore more readily accepted by the public.The Ger-man phytoremediation sites in Leipzig has for instance,been well received by the inhabitants of the immediate vicinity.0045-6535/$-see front matter Ó2005Elsevier Ltd.All rights reserved.doi:10.1016/j.chemosphere.2005.08.042*Corresponding author.Tel.:+492418026686;fax:+492418022182.E-mail address:evangelou@bio5.rwth-aachen.de (M.W.H.Evangelou).Chemosphere 63(2006)996–1004/locate/chemosphereAlthough all plants have the potential to extract met-als from soil,some plants have shown the ability to extract,accumulate and tolerate high levels of heavy metals.Such plants are termed hyperaccumulators, which are taxonomically widespread throughout the plant kingdom.Metal hyperaccumulation is an ecophys-iological adaptation to metalliferous soils(Maywald and Weigel,1997).The potential for application of hyperac-cumulators in bioremediation is limited by the fact that they are slow growing and have a small biomass.These characteristics are contrary to the ones proposed by Robinson et al.(2000)who suggested that a plant used for phytoremediation should be fast growing,deep-rooted,easily propagated and accumulating the target metal.According to Ro¨mkens et al.(2002)it should also have a high biomass production.For these reasons the tobacco plant,Nicotiana tabacum is suitable for phyto-remediation,in the areas of Latin and South America.Chelators have shown an ability to enhance phyto-remediation of heavy metals from contaminated soil, an ability that could balance the characteristics of the hyperaccumulating plants.Although synthetic chelators, such as EDTA,have shown positive eﬀects on the enhancement of phytoextraction of metals from soil, their use has disadvantages:EDTA is non-selective in extracting metals(Barona et al.,2001)and has poor bio-degradability(Wasay et al.,1998).It has also the eﬀect of decreasing the plant growth severely(Chen and Cut-right,2001)even at very low concentrations.An alterna-tive to synthetic chelators could be found in naturally occurring chelating agents,the so called biochelators. Biochelators,such as humic acids,have already been shown to have positive eﬀects on the phytoextraction of heavy metals from soil(Evangelou et al.,2004). Another possible alternative is natural low molecular weight organic acids(NLMWOA),which are exudated by plants into the soil.It is known that exudation of organic compounds by roots may inﬂuence the solubility of essential and toxic ions indirectly and directly;indirectly,through their eﬀects on microbial activity,rhizosphere physical prop-erties and root growth dynamics and,directly,through acidiﬁcation,chelation,precipitation and oxidation–reduction reactions in the rhizosphere(Uren and Reisenauer,1988;Marschner et al.,1995).Of these com-pounds,NLMWOA are of particular importance due to their complexing properties,which play a signiﬁcant role in heavy metal solubility(Mench and Martin,1991; Krishnamurti et al.,1997;Nigam et al.,2000)and the mobilization of mineral nutrients(Zhang et al.,1989; Jones et al.,1996),even more important than the pH of the soil(Huang et al.,1998).The objective of this research was to investigate the ability of NLMWOA in enhancing the phytoextraction of copper and lead from soil by the use of tobacco plants under laboratory conditions.The potential of NLMWOA in replacing compounds such as EDTA or other synthetic chelators as enhancing agents for the phytoremediation of heavy metal contaminated soils was assessed.2.Materials and methods2.1.Soil characterizationA silty–loamy sand agricultural soil,USDA(Soil Survey Manual,1995),was collected from0to30cm surface layer of the Melatenﬁeld in Aachen,Germany. The soil was air-dried at room temperature,sieved through a2-mm sieve and characterised as follows. The sand,clay and silt fractions of the samples were determined by the hydrometer methods(Bouyoucous, 1952).Organic matter content was determined by the Walkley–Black method(Nelson and Sommers,1996). The pH was measured by the CaCl2-method(Lewan-dowski et al.,1997).The initial total copper and lead content of the soil,as determined by the aqua regia method after DIN38414Teil7,Copper and lead analy-sis in theﬁltrate was performed byﬂame AAS(Perkin–Elmer1100B).Standards for the AAS calibration were prepared in the extraction solution by the addition of appropriate quantities of copper and lead respectively. The soil properties are listed in Table1.2.2.Pot experiments2.2.1.Soil preparationThe pot experiments were conducted in a greenhouse from March to April.Four-hundred grams of air-dried and sieved soil wasﬁlled in0.5l plastic pots with six small holes at the bottom.The plastic pots were pre-washed with dilute nitric acid to eliminate any adsorbed metals.A pot-plate was placed under each pot.To each pot the following amounts of fertilizer were applied: 674.4mg Ca(NO3)2Æ4H2O,175.6mg KH2PO4,resulting in a concentration of200and100mg kgÀ1respectively. Table1Selected properties and heavy metals concentrations of the used soilParameters ContentpH 6.8Organic matter(%) 3.5Soil fractionsSand(%)49.4Clay(%)42.1Silt(%)8.5Copper(mg kgÀ1)21.8Lead(mg kgÀ1)48.7M.W.H.Evangelou et al./Chemosphere63(2006)996–10049972.2.2.Seedling preparation and plant growthTobacco plants(N.tabacum SR-1)were used for the pot experiments.This selection was based on the plantÕs ability to produce a relative great biomass in a very short time.Seeds of tobacco plants were germinated in a peat/ sand mixture.After3weeks,seedlings with similar bio-mass were used for the pot experiments.All tobacco plants were grown under controlled envi-ronmental conditions with a16h light period(light intensity of320l mol mÀ2sÀ1),a25/20°C light/dark temperature regime,and60%relative humidity(Walch-Liu et al.,2000).2.2.3.Toxicity pot experimentThe experiment included the control treatment(no additional chelating agents),and treatments with62.5, 125,and250mmol kgÀ1for the NLMWOA and0.125, 0.25,0.25,62.5,125,and250mmol kgÀ1for EDTA.On the day of the chelating agentsÕapplication,seedlings with similar biomass were transferred into the pots containing the metal and NLMWOA spiked soil.One seedling was planted into each pot,thereafter,the experiment was ini-tiated.The experiment was performed in triplicates.The toxicity eﬀects were observed with the aid of the dry mass.2.2.4.Phytoextraction pot experimentsThe experiments included the control treatments(no additional heavy metals),and treatments with225and 450mg kgÀ1copper applied as CuCl2and300and 600mg kgÀ1lead applied as Pb(NO3)2.Each treat-ment was performed in triplicates.One day after the application of copper or lead,the fertilizers,and 62.5mmol kgÀ1NLMWOA(citric,oxalic,and tartaric acid)or0.125mmol kgÀ1EDTA were applied and sub-sequently one seedling was placed on each pot,thereaf-ter the experiment was initiated.All seedlings used had similar biomass.In order to avoid the leaching of copper and lead from the soil the distilled water,which was used for watering the plants was never added directly to the soil surface,but into the pot-plate.2.2.5.Plant harvest and analysisPlants used in the pot experiments were harvested after approximately3weeks of growth.During harvest, plants were cut short above ground,and separated into stem and leaves.The subsequent steps were performed according to Jones and Case(1990).Plant samples(stem and leaves)were rinsed brieﬂy in deionised water,dried between Kleenex tissues to remove surface contamina-tion,and oven dried at70°C to a constant weight. The dry weight was determined and the samples were homogenised in particle size by grounding in a ball mill.After milling,200±5mg of dried plant tissue were weighed into a15ml high form porcelain crucible.The plant tissue was ashed at500°C for5h in a muﬄe fur-nace and cooled down.At60°C,2ml of15%HCl were added and evaporated.At room temperature,2ml of 15%HCl were again added.The ash was suspended with the assistance of a glass stick,and the suspension subse-quentlyﬁltered through a quantitativeﬁlter paper(595, Schleicher and Schuell Filters,pore size4l m).Theﬁl-trate was adjusted to20ml with deionised water and analysed for copper and lead by AAS.2.3.Slurry experimentOne gram of the agricultural soil was weighed into a 50ml polypropylene copolymer centrifuge tube.The centrifuge tubes were pre-washed with dilute nitric acid to eliminate any adsorbed metals.The soil was suspended with15ml of a62.5mM solution containing, either,citric acid,oxalic acid,tartaric acid or0.125mM EDTA.Each suspension was performed at three diﬀer-ent pH values,9,7,and5adjusted with1M NaOH. The tubes were shaken for18h at70rpm,and subse-quently the tubes were centrifuged at14.000g for 10min.Each sample was thenﬁltered through a quanti-tativeﬁlter paper(595,Schleicher and Schuell Filters, pore size4l m).In order to conserve the samples 100l l of65%HNO3was added to each of them.The copper and lead content in the solution was performed by AAS.Each treatment was performed in triplicates.2.4.Column experimentGlass columns(24mm inner diameter and140mm in length)were used in this study.The columns were pre-washed with dilute nitric acid to eliminate any adsorbed metals.Spiked soil,25g containing450mg kgÀ1of cop-per applied as CuCl2and600mg kgÀ1of lead applied as Pb(NO3)2,was packed into the column.The soil was spiked3months before the column experiment,and it was achieved by the application of large volumes of dis-solved CuCl2and Pb(NO3)2at low concentrations in order to achieve an equal distribution.The pore volume of the column,which was determined after DIN19683-13was56%,which equals14ml.The solution was ponded,about6cm above the soil surface,on the column and maintained during the leaching.The eﬄuentﬂow rate was kept at an average of1pore volume hÀ1 (14±1ml hÀ1).Each column was eluted with60–100ml of62.5mM citric acid,oxalic acid,tartaric acid, 0.125mM EDTA,or10mM CaCl2solution respectively. The solution level varied slightly according to leachate ﬂow.At the bottom of the columns,the leachates were collected in14ml aliquots and measured at the same day.To avoid pH dependent eﬀects chelating agentsÕsolu-tions were adjusted to a pH value of6.8with1M NaOH, which is the soilÕs pH value.The solution of10mM CaCl2 has comparable ionic strength to the natural soil solutions (Shuman,1990).CaCl2serves as a control and to give hints for the later phytoextraction experiment.Each solu-998M.W.H.Evangelou et al./Chemosphere63(2006)996–1004tion-column experiment was performed inﬁve replicates. The copper and lead content was determined by AAS.2.5.Statistical analysisEach copper and lead concentration and each chelat-ing agent concentration was performed in triplicates (n=3)except for the column experiment,which was performed inﬁve parallels(n=5).The diﬀerence between speciﬁc pairs of means was identiﬁed by t-test (P<0.05).Statistical analysis of the data was performed by using Excel XP(Microsoft).3.Results3.1.Toxicity pot experimentDry matter yields of the shoots(sum of leaves and stem)are shown in Fig.1.The application of NLMWOA to the soil did not adversely aﬀect dry matter production of the plants at a concentration of62.5mmol kgÀ1,but toxicity symptoms such as lower dry weight and chlorosis were visible for higher concentrations of these chelating agents.Citric acid showed already signiﬁcant(P<0.05) toxicity eﬀects at a concentration of125mmol kgÀ1.Tar-taric acid and oxalic acid showed only slight toxicity at this concentration.EDTA did not show any adverse eﬀects at a concentration of<0.125mmol kgÀ1.At 1.25mmol kgÀ1of EDTA(Fig.1b)the leaves showed necrotic lesions and the dry weight was negligible.At a concentration of0.25mmol kgÀ1EDTA the dry weight is only slightly lower but the standard deviation is higher in comparison to the0.125mmol kgÀ1application.3.2.Phytoextraction pot experimentFig.2shows that copper and lead concentrations in the shoots,increased with increasing copper and lead concentrations in the soil.The uptake of copper in the shoots was particularly enhanced with citric acid.The treatment with62.5mmol kgÀ1citric acid caused a sig-niﬁcantly(P<0.05)higher concentration of copper in the shoots as compared to the control,and the other NLMWOA and EDTA applications.In the case of citric acid application copper concentrations in the shoots reached67mg kgÀ1.The eﬀect of oxalic and EDTA additions on copper plant uptake was less prominent, but nevertheless showed an increase in comparison to both the control and tartaric acid.Tartaric acid addition on copper plant uptake showed no enhancing eﬀect.In the case of lead only EDTA showed an enhancing eﬀect, and the shoots contained approximately63mg kgÀ1of lead.The application of the NLMWOA had no signiﬁ-cant(P<0.05)eﬀect,and the uptake of lead averaged to the same order of magnitude as the control.3.3.pH changeThe pH-values at the beginning and at the end of the phytoextraction experiments are shown in Table2.At the beginning of the experiment the pH value of the con-trol soil was0.3lower than its native pH,probably through the application of fertilizers.The application of copper and lead further decreased the pH.At the end of the experiment the control soil reached its native pH.In the case of EDTA,the pH changes were similar as in the case of control.The application of NLMWOA lowered the pH to an average value of5.6at the begin-ning of the experiment.At the end of the experiment the pH reached values in average around7.7,which is0.9 higher than the native pH of the soil.3.4.Slurry experimentFig.1shows the copper and lead mobilisation in percentage,of the natural contaminated soil,whichM.W.H.Evangelou et al./Chemosphere63(2006)996–1004999contained 21.8and 48.7mg kg À1copper and lead respectively.The mobilised copper by the NLMWOA was signiﬁcantly (P <0.05)higher in comparison to that of EDTA.The amounts mobilised by the diﬀerent NLMWOA were in the same order of magnitude.The NLMWOA mobilised approximately 20–25%of copper (Fig.3a)and approximately 8%of lead (Fig.3b)refer-ring to the initial concentrations.Whilst the diﬀerence between the NLMWOA and EDTA in the mobilisation capability of copper was very high,mobilisation of lead amounts was of the same order of magnitude.Only citric acid at pH 5stands out with a lead mobilisation of approximately 36%.The amounts mobilised by milli-pore water (control)approximately 1%copper and 0.5%lead have been subtracted.3.5.Column experimentFig.4depicts copper and lead mobilised from a soil spiked with 450copper and 600mg kg À1lead respec-tively,through a column experiment,in percentage of the total amount of copper and lead in the soil.The cop-per mobilised by NLMWOA was to a signiﬁcant (P <0.05)extent higher than by EDTA.EDTA mobi-lised approximately 0.4%more than CaCl 2but both average out at the same order of magnitude.In compar-ison to the NLMWOA,the control with CaCl 2and EDTA mobilised negligible amounts of copper.Citric acid mobilised the most in the ﬁrst fraction,approxi-mately 25%.The mobilised amounts declined with the number of pore volumes.Oxalic and tartaric acid reached their maximum at the fourth pore volume,but mobilised only approximately 9%and 3%respectively.Table 2The soil pH before and after the growth of tobacco plants for 3weeks in soil spiked with copper (panel A)and lead (panel B)and treated with NLMWOA and EDTA Application Control Cu 225Cu 450pH start pH end pH start pH end pH start pH end Panel A Control 6.46±0.09 6.79±0.08 6.23±0.02 6.67±0.02 6.18±0.01 6.64±0.14Citric acid 5.65±0.077.45±0.06 5.54±0.047.44±0.08 5.48±0.117.45±0.04Oxalic acid 5.66±0.057.64±0.06 5.42±0.017.73±0.11 5.42±0.017.73±0.11Tartaric acid 5.72±0.037.45±0.10 5.62±0.037.71±0.01 5.53±0.037.76±0.09Na 2EDTA6.40±0.09 6.83±0.106.36±0.03 6.67±0.036.36±0.03 6.67±0.03Control Pb 300Pb 600pH startpH end pH start pH end pH start pH end Panel B Control 6.46±0.09 6.79±0.08 6.41±0.03 6.73±0.03 6.19±0.01 6.91±0.07Citric acid 5.65±0.077.45±0.06 5.48±0.037.41±0.00 5.34±0.04 6.91±0.07Oxalic acid 5.66±0.057.64±0.06 5.55±0.087.59±0.08 5.54±0.017.68±0.12Tartaric acid 5.72±0.037.45±0.10 5.65±0.047.80±0.07 5.65±0.047.71±0.10Na 2EDTA6.40±0.096.83±0.10 6.38±0.146.90±0.01 6.40±0.016.78±0.151000M.W.H.Evangelou et al./Chemosphere 63(2006)996–1004The lead mobilised by NLMWOA,EDTA,and CaCl 2ranged at the same order or magnitude,between 0.5%and 2%.In comparison to oxalic and tartaric acid,citric acid showed a diﬀerent extraction curve in the extraction of lead and copper.In the extraction of lead the curve reached its maximum in the second pore volume.4.DiscussionThe phytotoxicity experiments depicted a great diﬀer-ence between NLMWOA and EDTA concerning their toxicity to plants.EDTA showed a very high toxicity (Fig.1b),as reported by Chen and Cutright (2001),and revealed a decreased plant growth at the concentra-tion of 1.25mmol kg À1in soil.At EDTA concentration of 0.125mmol kg À1in soil the plants showed no toxicity symptoms and had a very small variation among the triplicates.At 0.25mmol kg À1,the dry weight is similar to that of the control,but the standard deviation is very high,so that a lower concentration was chosen for the phytoextraction experiments (Fig.1b).The NLMWOAapplication of 62.5mmol kg À1showed no adverse eﬀects on the dry matter production of the shoots,and even a slight increase in shoots yield is visible (Fig.1a),as a consequence this concentration was chosen for the phytoextraction experiment.Higher concentrations of NLWOA resulted in biomass decrease,probably due to the destruction of the physiological barrier by NLMWOA in roots which controls the uptake of solutes (Vassil et al.,1998).NLWOA may damage the plasma membranes which are normally stabilised by Ca 2+and Zn 2+ions (Pasternak,1987;Kaszuba and Hunt,1990)and may confer random metal complexes of soil–solu-tion access to root xylem and to the shoot via the tran-spiration stream (Vassil et al.,1998).Prior to the organic acid toxicity tests,copper and lead toxicity experiments were performed.These showed no apparent harmful eﬀects of copper or lead on the plants for a soil copper content of 450mg kg À1and a soil lead content of 600mg kg À1(data not shown).The analysis of plant material indicated that citric acid (62.5mmol kg À1)and EDTA (0.125mmol kg À1)M.W.H.Evangelou et al./Chemosphere 63(2006)996–10041001treated soil signiﬁcantly(P<0.05)increased the concen-trations of copper in the shoots by2.3and1.1-fold respectively in comparison to the control plants (Fig.2).The increase by the addition of EDTA and NLMWOA was not as high as stated by Schmidt (2003)and Gramss et al.(2004)respectively.Although tartaric acid showed mobilisation potential equal to that of citric acid,at all pH values,(Fig.3)it did not increase the copper concentrations in the shoots(Fig.2).Oxalic acid increased the copper concentration in the shoots in the same order of magnitude as EDTA.The plant analysis,revealed that the NLMWOA had no enhancing eﬀect in the uptake of lead into the plants,although NLMWOA treatments showed higher mobilisation capabilities in slurry(Fig.3b)and column experiments (Fig.4b)than EDTA.EDTA showed an approximately 3-fold increase of lead concentration in the shoots (Fig.2),which is still lower from that stated by Grcman et al.(2001).Regarding that the concentration of NLMWOA in the soil used in the phytoextraction experiment was250times higher than EDTA the eﬀect was minimal even for copper spiked soil.At the dosage used in phytoextraction,EDTA is equally ineﬀective. EDTA is only eﬀective at rates where toxic eﬀects are visible and leaching losses exceed plant uptake.In the slurry experiments the addition of62.5mM NLMWOA showed an enhanced mobilisation of copper in comparison to by the addition of0.125mM EDTA (Fig.3a),while the addition of NLMWOA showed very little eﬀect in the mobilisation of lead than EDTA (Fig.3b).Only citric acid(Fig.3b)at pH5mobilised a lot more lead than EDTA and oxalic and tartaric acid. One reason could be a combination of the low pH value and the salt carriage,as a result of the pH adjustment, which would result in higher heavy metal mobilisa-tion.Copper solubility increases with decreasing pH (Schmidt,2003).This individual experiment was repeated several times and the results were always the same.The column experiment underlined the great diﬀer-ence between the two metals copper and lead concerning their extractability by NLMWOA and the diﬀerence between the complexation capabilities of the NLMWOA tested.Lead mobilisation by NLMWOA was very low (Fig.4b).This supports the lead phytoextraction results that only EDTA was able to enhance the uptake.Cop-per mobilisation by NLMWOA,especially citric acid, was signiﬁcantly(P<0.05)higher than the copper amounts extracted by EDTA(Fig.4a).Regarding the potential of NLMWOA as shown in the column experiments,and in combination with the fact that the spiked soil used in the phytoextraction experiment had not passed a normal wet-dry cycle (2months),the uptake had to be much more enhanced. This indicates that this technique will probably fail underﬁeld conditions.The lack of high eﬃciency of the method was probably attributed to biodegradation of the NLMWOA.Which is reﬂected by the increase in pH,resulting from consumption of H+from carbox-ylic acids and liberation of OHÀand CO2(Gramss et al., 2004).This results in the lacking of complexing agents and a pH increase,which reduce the bioavailability of copper and lead.Copper is more mobile in soil than lead and therefore extracted from the plants before degrada-tion of the organic acids.To explain the ineﬃciency for the technique,the lacking access into the plant is ruled out,because,as in the case of EDTA(Grcman et al., 2001),their complexes are translocated via xylem from the roots to the shoots(Senden et al.,1990;Guo, 1995).The eﬃciency of the technique could be raised if the NLMWOA would be applied a few days before har-vest.But regarding the fact that approximately6g of cit-ric acid had to be applied on each pot makes the method rather expensive.Additionally,the bioavailability of metals is connected to the pH of the soil(Schmidt, 2003)and theﬁnal pH of the soil where NLMWOA were applied was approximately7.7,thus reducing the bioavailability of copper and lead.Therefore,making a continuous application of NLMWOA unsuitable for a clean up over several years.Alternatives to NLMWOA could be other biode-gradable chelating agents as nitrilo-triacetic acid (NTA)(Bolton et al.,1996)and[S,S0]-ethylenedia-mine–disuccinic acid(EDDS)(Jones and Williams, 2001).NTA is a very strong chelating agent compared to NLMWOA(Elliot and Denneny,1982),but neverthe-less the enhancement by a factor of2.5compared with the controls is insuﬃcient for phytoremediation applica-tions(Kulli et al.,1999).EDDS,a naturally occurring substance,isolated from Amycolatopsos orientalis (Nishikiori et al.,1984)has shown potential but the con-centrations achieved in Grcman et al.(2003)were still very far away from the concentrations required for eﬃ-cient phytoextraction.5.ConclusionNLMWOA,especially citric acid had a positive eﬀect on copper bioavailability and enhanced the copper uptake2.3-fold.In addition,they do not have the nega-tive eﬀects caused by phytotoxic EDTA such as the severe decrease in shoot biomass at very low concentra-tions in the soil.However,not only were they ineﬃcient in lead phytoextraction,but also the amounts of NLMWOA,which had to be applied to the soil before any eﬀect was visible,were high.In this aspect EDTA was much more eﬃcient.It is probable that the ready biodegradation of the NLMWOA was responsible for this lack of eﬃciency.They are probably degraded much too quickly to have the desired eﬀect NLMWOA are therefore not suitable for the enhancement of phytoex-traction,and will not serve as an economic alternative1002M.W.H.Evangelou et al./Chemosphere63(2006)996–1004to synthetic chelators.We will continue research in investigating other natural chelators to replace synthetic chemicals for this purpose.AcknowledgementsWe would like to thank the technical assistants,for their technical help during the research period and Ingolf Schuphan,Rong Ji,Philippe Corvini,Shelley Obermann,for their invaluable help.ReferencesBarona,A.,Aranguiz,I.,Elias,A.,2001.Metal associations in soils before and after EDTA extractive decontamination: implications for the eﬀectiveness of further cleanup proce-dures.Environ.Pollut.113,79–85.Bolton,H.,Girvin Jr., C.C.,Plymale, A.E.,Harvey,S.D., Workman,D.J.,1996.Degradation of metal–nitriloacetate complexes by Chelatobacter heintzii.Environ.Sci.Technol.31,860–865.Bouyoucous,G.J.,1952.A recalibration of hydrometer for making mechanical analysis of soils.Agron.J.43,434–438. Chen,H.,Cutright,T.,2001.EDTA and HEDTA eﬀects on cadmium,Cr,and Ni uptake by Helianthus annuus.Chemosphere45,21–28.Deutsches Institut fu¨r Normung e.V DIN19683Teil13,1997-03. Deutsches Institut fu¨r Normung e.V DIN38414Teil7,1983-01. Elliot,H.A.,Denneny,C.M.,1982.Soil adsorption of Cd from solutions containing organic ligands.J.Environ.Qual.11, 658–663.Evangelou,M.W.H.,Daghan,H.,Schaeﬀer, A.,2004.The inﬂuence of humic acids on the phytoextraction of cadmium from soil.Chemosphere57,207–213.Gramss,G.,Voigt,K.D.,Bergmann,H.,2004.Plant availabil-ity and leaching of(heavy)metals form ammonium-, calcium-,carbohydrate-,and citric acid-treated uranium-mine-dump soil.J.Plant Nutr.Soil Sci.167,417–427. Grcman,H.,Velikonja-Bolta,S.,Vodnik,D.,Kos,B.,Lestan,D.,2001.EDTA enhanced heavy metal phytoextraction:metal accumulation,leaching and toxicity.Plant Soil235, 105–114.Grcman,H.,Vodnik,D.,Velikonja-Bolta,S.,Lestan,D.,2003.Ethylenediaminedissucinate as a new chelate for environ-mentally safe enhanced lead phytoextraction.J.Environ.Qual.32,500–506.Guo,Y.,1995.Genotypic Diﬀerences in Uptake and Translo-cation of Cadmium and Nickel in Diﬀerent Plant Species.Verlag Ulrich E Grauer,Stuttgart.Huang,J.W.,Blaylock,M.J.,Kapulnik,Y.,Ensley,B.D.,1998.Phytoremediation of uranium-contaminated soils:role or organic acids in triggering uranium hyperaccumulation in plants.Environ.Sci.Technol.32,2004–2008.Jones,J.B.,Case,V.W.,1990.Sampling,handling and analyz-ing plant tissue samples.In:Westerman,R.L.(Ed.),Soil Testing and Plant Analysis,third ed.,Soil Science Society of America Book Series,vol. 3.Soil Science Society of America,Madison,WI,pp.389–427.Jones, D.L.,Darrah,P.R.,Kochian,V.L.,1996.Critical evaluation of organic acid mediated iron dissolution in the rhizosphere and its potential role in root iron uptake.Plant Soil180,57–66.Jones,P.W.,Williams,D.R.,2001.Chemical speciation used to asses[S,S0]-ethylenediamine–disuccinic acid(EDDS)as a readily-biodegradable replacement for EDTA in radiochem-ical decontamination formulations.Appl.Radiat.Isot.54, 857–893.Kaszuba,M.,Hunt,G.R.A.,1990.Protection against mem-brane damage:a H NMR investigation of the eﬀect of Zn2+ and Ca2+on the permeability of phospholipid vesicles.J.Inorg.Biochem.40,217–225.Krishnamurti,G.S.R.,Cieslinski,G.,Huang,P.M.,Van Rees, K.C.J.,1997.Kinetics of Cd released from soils as inﬂuenced by organic acids implication in cadmium avail-ability.J.Environ.Qual.26,271–277.Kulli,B.,Balmer,M.,Krebs,R.,Lothenbach,B.,Geiger,G., Schulin,R.,1999.The inﬂuence of nitrilotriacetate on heavy metal uptake of lettuce and ryegrass.J.Environ.Qual.28, 1699–1705.Lewandowski,J.,Leitschuh,S.,Kob,V.,1997.Schadstoﬀe im Boden.Springer-Verlag,Heidelberg.Marschner, B.,Henke,U.,Wessolek,G.,1995.Eﬀects of meliorative additives on the adsorption and binding forms of heavy-metals in a contaminated topsoil from a former sewage farm.Z.Pﬂanz.Bodenkunde158,9–14. Maywald,F.,Weigel,H.J.,1997.Biochemistry and molecular biology of heavy metal accumulation in higher plants.Landbauforsch.Volk.47,103–126.Mench,M.,Martin,E.,1991.Mobilization of cadmium and other heavy metals from2soils by root exudates of Zea-Mays L.,Nicotiana-Tabacum-L.and Nicotiana-Rustica L.Plant Soil132,187–196.Nelson,D.W.,Sommers,L.E.,1996.Total carbon,organic carbon,and organic matter.In:Sparks,D.L.,Page,A.L., Helmke,P.A.,Loeppert,R.H.,Soltanpour,P.N.,Tabata-bai,M.A.,Johnson,C.T.,Sumner,M.E.(Eds.),Methods of Soil Analysis:Part 3.Chemical Methods.,SSSA Book Monograph,vol.5.SSSA,Madison,WI.Nigam,R.,Srivastava,S.,Prakash,S.,Srivastava,M.M.,2000.Cadmium mobilisation and plant availability—the impact of natural organic acids commonly exuded from roots.Plant Soil230,107–113.Nishikiori,T.,Okuyama, A.,Naganawa,H.,Takita,T., Hamada,H.,Takeuchi,T.,Aoyagi,T.,Umezawa,H., 1984.Production by actinomycetes of(S,S)-N,N0-ethylene-diamine–disuccinic acid,an inhibitor of phospholipase.C.J.Antibiot.37,426–427.Pasternak,C.A.,1987.A novel form of host defense:membrane protection by Ca2+and Zn2+.Biosci.Rep.7,81–91. Raskin,I.,Smith,R.D.,Salt,D.E.,1997.Phytoremediation of metals:using plants to remove pollutants from the environ-ment.Curr.Opin.Biotechnol.8,221–226.Robinson,B.H.,Millis,T.M.,Petit,D.,Fung,L.E.,Green, S.R.,Clothier,B.E.,2000.Natural and induced cadmium-accumulation in poplar and willow:implications for phyto-remediation.Plant Soil227,301–306.Ro¨mkens,P.,Bouwman,L.,Japenga,J.,Draaisma,C.,2002.Potentials and drawbacks of chelate-enhanced phytoreme-diation of soils.Environ.Pollut.116,109–121.M.W.H.Evangelou et al./Chemosphere63(2006)996–10041003。

香根草在土壤修复中的研究及应用

深处,能够与土壤紧密固结等优势,被认为是治理水
量、速效磷量、微生物量及酶的活性,具有土壤改良的
土流失的首选植物之一,也被称之为 “ 世界上具有最
作用。曹红梅等 [ 22] 利用人工种植香根草修复铜尾矿
长根系的草本植物。
废弃地发现香根草能不断富集重金属铜,直至达到饱
中的污染物也有一定的富集作用,因此被广泛地应用
香根草的适应性,同时也可增强香根草的修复效果。
水土保持项目及土壤修复等领域中,尤其是对各种废
利用垃圾( 占比为 25% ~ 50% ) 来改良铅
弃的矿山及垃圾填埋场等土壤修复。香根草不仅可
锌尾矿,结果发现适当地添加垃圾改良尾矿不仅能提
土矿山修复技术之一。
李冰等
[ 15]
mg / L 时,其叶绿素含量及各种酶的活性均比对照组
变高,超过 500 mg / L 时,它们才有所下降,这也表明
了香根草对铅离子具有较强的耐抗性。杨雪艳等 [ 24]
利用双耐细菌与香根草相结合来修复铅镉复合污染
2. 2 土壤修复
和,且多数集中在香根草根部,同时也增加了其基质
2. 2. 1 稀土矿山的修复
中的微生物数量及酶活性,认为香根草是一种良好的
目前开采离子型稀土矿山使用的浸出剂为硫酸
具有修复铜尾矿废弃地潜力的植物。
铵,在浸出过程中会残留大量的铵盐和少量的稀土元
林杰等 [ 23] 研究了铅离子浓度对香根草叶片膜及
植在矿山上,由于矿山具有贫瘠性等特点,限制了其

2024届陕西省榆林市高三下学期第四次模拟考试英语试题

2024届陕西省榆林市高三下学期第四次模拟考试英语试题一、阅读理解Making tiny furniture is no piece of cake. In this course, join Amanda Kelly, who is now pursuing her Master’s degree of Fine Arts in Sculpture at Radford University, to learn how to create realistic furniture from the beginning. While students who have taken this course are highly encouraged to sign up, students of all levels are welcomed!Course OverviewThis course includes five sessions, each lasting for 2 hours on five Tuesdays beginning on July 9.Session 1 (Tuesday, 7/9, 7 — 9: 00 PM) Foundations and ScaleSession 2 (Tuesday, 7/16, 7 — 9: 00 PM) Making the Side TableSession 3 (Tuesday, 7/23, 7 — 9: 00 PM) Making the BedSession 4 (Tuesday, 7/30, 7 — 9: 00 PM) One Person’s Waste Is Another’s Tiny Treasure Session 5 (Tuesday, 8/6, 7 — 9: 00 PM) Sharing Your Creations Pricing OptionsIn addition to full-price tickets of $ 225, a limited number of no-pay tickets are available for this course. Please note that these tickets are reserved for those who would not otherwise be able to take this course and who expect to attend all sessions. No-pay tickets are distributed via a random drawing two weeks before each course begins. For more information and to apply for a no-pay spot, please click here.What Else to KnowThis is an interactive, small-group workshop. Students are encouraged to participate in discussions and work on assignments outside of class. Due to the interactive nature of this course, we strongly recommend students attend as many live sessions as possible. If students are unable to attend the live sessions, after each session they will receive access to a recording of the live session, which they can watch for up to two weeks after the course concludes.1．In which section will students make the bed?A．Session 2.B．Session 3.C．Session 4.D．Session 5. 2．What can students do if they miss a live session?A．Reach out to other students.B．Email the instructor immediately.C．Watch the recorded class within 14 days.D．Make up for the class within 72 hours.3．Which of the following is TRUE?A．The course will last for about two months.B．A large number of no-pay tickets are available for the course.C．Only experienced students can join the course.D．Students can get more information about the course on a website.On Nov 7, 52-year-old French author Jean-Baptiste Andrea secured the famed Goncourt Prize for his novel Watch Over Her. With a history of 120 years, the Goncourt Prize stands as one of the most important literary awards in France.Described as “extremely refreshing”, the book offers readers a break from a sad new cycle, according to Didier Lecoin, the jury (评委会) president of the Goncourt Prize. Philippe Claudel, another member, said it was “high-quality popular literature”. “And that is what the Goncourt is about,” he added.Watch Over Her develops as a love story between a young poor sculptor and a local noble young woman in 20th -century Italy, during the rise of fascism (法西斯主义). The account skillfully combines their story of love with explorations of Italian history and political structures.Andrea mentioned that he crafted the story of Watch Over Her because he desired to reconnect with Italy, “the country of my ancestors”, and because he firmly believed in the power of popular fiction.Andrea, a former screenwriter and director who turned to novel writing in his 40s, expressed that writing novels allowed him to rediscover the joy of writing lost in filmmaking. For him , writing is a means of taking control of his life, representing a return to his childhood passion for storytelling.While some critics suggested that Watch Over Her might challenge the traditionally elite (精英) image of the Goncourt Prize, Andrea thought differently in an interview with France Inter, stating, “I feel that today we’ve left the privilege of telling stories to cinema... as if telling a story excluded depth. But I think we can be popular and at the same time deep, and give different levels of reading to different types of readers and generations.”4．What is the purpose of the first paragraph?A．To lead into the topic of the passage.B．To introduce a new literary award.C．To present one of the major views of the society.D．To draw readers’ attention to writing.5．What do people think of Watch Over Her?A．It is highly thought of by all.B．It offers an escape from sorrow.C．It elevates high-quality literature.D．It provides access to science fiction. 6．Why did Andrea return to novel writing?A．He is interested in exploring storytelling methods.B．He hopes to find a sense of inner peace.C．He needs to seek further inspiration for filmmaking.D．He wants to fulfill his childhood dream.7．What do we know about Watch Over Her?A．It is a short story set in 19th-century Italy.B．It is a historical exploration of French politics.C．It represents Andrea’s way of revisiting his roots.D．It involves a young sculptor and a poor woman.Philippine pineapple farmers used to be bothered by pineapple leaves. Fortunately, their trouble has been removed by Carmen Hijosa, a Spanish researcher who spent eight years developing a new textile (纺织物) she calls Pinatex. This kind of new cloth materials, made from pineapple leaf fibres which are harvested and stripped from pineapple leaves by farmers, are very fine and strong and flexible. These characteristics make them quite popular.Since launching commercially in the mid-2015, Pinatex has been used by about 500 producers including a recent cooperation with fashion house Hugo Boss on a pair of vegan sneakers. Smaller fashion companies have been inspired by its unique look and feel.Timothy Turner, creative director for fashion brand Altiir whose entire collection of biker style jackets are made from Pinate x says, “it’s got a unique texture. I’ve worn this for about a year, and it ages to your body really gracefully and shapes to your body when it gets wet; it dries like leather, and it behaves like leather in every way except it’s completely sustainable.”The long fibre is pulled out through a process called decortication (去皮), which is done atthe plantation by the farming community. Ananas has developed the first automated decorticating machine to assist with this process, allowing farmers to use greater quantities of their waste leaves. Once the leaves have been stripped of fibre, the leftover biomass can be used as a nutrient-rich natural fertilizer or a biofuel, so nothing is wasted. The fibre then gets degummed (脱胶) and undergo an industrial process to become a non-woven material, which forms the base of Pinatex.The rolls of non-woven materials are then transported to Spain for specialised finishing. This unique process is what gives Pinatex its leather-like appearance, creating a textile that is soft and flexible, yet very strong. The finished textile is distributed to designers directly by Ananas Anam, who uses it as a sustainable alternative to leather in footwear and fashion accessories, clothing, interior furnishing and automotive cushions.8．What does the author intend to do in Paragraph 2?A．To promote a new product from Hugo Boss.B．To call for cooperation between companies.C．To provide evidence of Pinatex’s popularity.D．To inspire smaller fashion industries.9．What is Pinatex’s advantage over leather?A．It’s stronger and more flexible.B．It is environmentally friendly.C．It is more popular in industries.D．It consumes more pine leaves.10．What is the main idea of Paragraph 4?A．How is the machine developed.B．How is the leftover dealt with.C．How is the new textile produced.D．How is fibre stripped from leaves. 11．What is the best title for the passage?A．A Textile Made from Leaves B．An Annoyance of FarmersC．A Low-carbon Lifestyle D．A Revolution in AgricultureThe rate of childhood obesity in the U. S. has tripled over the past 50 years. The American Academy of Pediatrics (AAP) made waves this year by recommending that doctors put obese kids as young as two years old on intensive, family-oriented lifestyle and behavior plans. It also suggested prescribing weight-loss drugs to children 12 and older and surgery to teens 13 and older. This advice reflects the organization’s adoption of a more active position on childhood obesity.Yet the lifestyle programs the AAP recommends are expensive, inaccessible to most children and hard to maintain. Few weight-loss drugs have been approved for children. And surgery has potential risks and few long-term safety data. Furthermore, it’s not clear whether interventions in youngsters help to improve health or merely add to the psychological burden overweight kids face from the society.Rather than paying close attention to numbers on a scale, the U. S. and countries with similar trends should focus on an underlying truth:we need to invest in more and safer places for children to play where they can move and run around, climb and jump, ride and skate.Why is it so hard to get kids moving? Experts blame the problem on the privatization of sports — as public investment in school-based athletics dwindles, expensive private leagues have grown, leaving many kids out. In addition to fewer opportunities at school, researchers cite increased screen time and a lack of safe places for them to play outside the home. New York City, for example, had 2,067 public playgrounds as of 2019 — a very small amount for its large population. In Los Angeles in 2015, only 33 percent of youths lived within walking distance of a park.Kids everywhere need more places to play. Public funding to build and keep up these areas is crucial, but other options such as shared-use agreements can make unused spaces available to the public. These opportunities aren’t primarily about changing children’s waistlines — they’re how we keep childhood healthy and fun.12．What can we learn from the first two paragraphs?A．Childhood obesity is well under control in recent years.B．Weight-loss surgery are recommended to children 12 and older.C．AAP plays a more active role in fighting against childhood obesity.D．Expensive as it is, lifestyle programs are practical for most children.13．What does the underlined word “dwindles” in Paragraph 4 probably mean?A．Decline.B．Quit.C．Increase.D．Develop.14．In the author’s opinion, what measure should be taken to create more safe areas?A．Preparing fitness equipment at home.B．Living within walking distance of a park.C．Promoting investment in private athletics.D．Opening up playgrounds when school’s out.15．Where can we probably read the passage?A．In a biography.B．In a newspaper.C．In a chemical paper.D．In a sports magazine.As a psychologist with more than 15 years of experience, I’ve seen how “hustle (忙碌) culture” can have a harmful effect on people. But a2 ,000 - year - old Chinese concept, “wu wei”, can help us lead more balanced, fulfilling and successful lives. “Wu wei” emphasizes taking action when necessary, but not pushing yourself with excessive effort and tension. 16 , while increasing satisfaction and overall well-being. Here’s how to make “wu wei” part of your daily routine.17 .Let’s say you’re throwing a big party. Instead of worrying about every detail, practicing “wu wei” means understanding that things may not go exactly as planned. When you face a challenge, ask yourself whether you have complete control over the outcome. If you don’t, make peace with it and move on.Embrace imperfection.Allow things to unfold in their own natural way, without forcing the outcome. Know that nothing is ever perfect. If you’re learning a new language or playing an instrument for the first time, prepare to make mistakes. 18Perform mindfulness.19 . Take notice of all the little details around you. How does the sun feel on your skin? Listen to the sounds of nature, like the birds and rustling leaves, or observe the shapes and colors of the flowers. “Wu wei” comes much easier when you pay attention to what’s happening in the present moment, in a friendly and curious way.Lao Tzu, an ancient Chinese philosopher and the founder of Taoism, once said: “If you are depressed, you are living in the past. If you are anxious, you are living in the future. 20 , you are living in the present.”A．You’ll learn from themB．Mind those catching your attentionC．Here’s some advice on how to be effortlessD．Mindfulness means being aware of your thoughts and feelings without judgement E．Accept things as they areF．If you are at peaceG．Research has shown that it can help lower stress and anxiety二、完形填空Mike Huddleston had flown from Maryland to San Francisco and 21 to get to a rental car agency. But 22 a neuromuscular(神经肌肉的) disease that weakens his muscles, he wouldn’t be able to 23 the stairs of the shuttle bus. As he was walking outside to meet his ride, he fell and couldn’t 24 .Due to his 25 , Huddleston needed something to push up on, like a bench or a chair. But there was nothing around that fit that 26 .“Out of nowhere, I hear in my left ear, ‘What can I do to 27 ? ‘” Huddleston turned his head to see a man in his late thirties 28 behind him. Huddleston described what the man could do to help him get off the 29 . Once he got him up, the man 30 Huddleston’s baggage, which had rolled a few feet away when he 31 .This encounter 32 Huddleston because of the way the man offered that kindness. He took a(n) 33 to ask Huddleston how he could help. “Different people may need 34 in different ways,” Huddleston 35 . “So asking them how you can help them is amazingly 36 . It allows the individual who’s in need of assistance to maintain a sense of 37 , to maybe feel a little less helpless, and maybe even a little less weak.”It’s been more than 20 years, but Huddleston 38 to think about it to this day. “His willingness to help me — and the love and sympathy he showed in a very 39 situation — for me is something I will 40 forget.”21．A．warned B．needed C．judged D．remembered 22．A．because of B．instead of C．rather than D．more than 23．A．climb B．notice C．forget D．blame 24．A．show off B．move in C．get up D．hold back25．A．insight B．position C．movement D．condition 26．A．description B．comment C．instruction D．adaptation 27．A．request B．save C．help D．promote 28．A．raising B．standing C．jumping D．holding 29．A．bus B．ride C．ground D．track 30．A．touched B．fetched C．sold D．gained 31．A．broke B．left C．slept D．fell 32．A．excited B．motivated C．puzzled D．struck 33．A．moment B．seat C．risk D．effort 34．A．guidance B．comfort C．protection D．assistance 35．A．defended B．explained C．argued D．sighed 36．A．difficult B．unusual C．helpful D．convincing 37．A．independence B．self C．trust D．relief 38．A．fails B．refuses C．intends D．continues 39．A．boring B．supportive C．challenging D．inspiring 40．A．never B．always C．often D．usually三、语法填空阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

提高学生学习成绩的方法

分分
分分
分分
①每周一、三、五，各写两个汉语成语，不要求背会，但必须写明日期、周几和序号。 ②每周一、三、五，各做一道数学题，并保存草演纸。 ③每周二、四、六，通过一句话记忆一个英语单
初一（一）中（二）末
初二（一）中
词（学过了但不会的也可以）。 ④每周二、四、
（二）末
六，各做一道理综题，且保存草演纸。 ⑤每周周末写一篇总结或周记，不应少于半页。 1．1．2 制定拟写计划的简捷办法
1．3．2 填表意义认真分析自己本次考试成功或失败的原因，具体落实到每一门课
上去总结经验和教训。弄清今后应抓什么课和怎么抓的关键问题。确定今后要赶上谁的奋斗目标，还要谨防谁超过自己；变成人与人的竞争后，个人会产生毅力和决心，班级将掀起你追我赶学习高潮。
2 培养毅力以提高成绩
通过知识与技能、过程与方法结合的貌似机械的实践操作，开展一计划两表技术训练，旨在培养学生顽强进取毅力、诚实积极态度、不屈不挠作风，确立正确的人生观和价值取向。从而达到有志学生活学活用技术的思想和方法，现在能苦学加巧学，提高学习成绩，为圆大学梦而不懈拼搏；将来能走出大山，融入社会，为实现伟大中国梦而尽绵薄之力！
表 4 曹妃甸地区优势植物的富集系数（BAC）
植物种类
Cu
As
Pb
Cd
八宝景天
0.5
0.096
0.498
0.37
野山楂
0.43
0.11
0.296
0.76
蒲公英
0.62
0.23
0.492
0.41
从表 4 可以看出，曹妃甸地区优势植物中，对 Cu、As、Pb、Cd 从何伏击能力较强的是蒲公英，其次是八宝景天，最后是野山楂。但是他们的富集系数均没有超过 1。

英国文学史及选读Chapter1

英国文学史及选读Chapter1英国文学史及选读Chapter1发布人：圣才学习网发布日期：2010-08-16 17:32 共270人浏览[大] [中] [小]The Anglo-Saxon PeriodI. Fill in the blanks.1.After the fall of the Roman Empire and athe withdrawl of Roman troops from Albion，the aboriginal __ population of the larger part of the island was soon conquerered and almost totally exterminated by the Teutonic tribes of ____，_____ ，and _____ who came from the continent and settled in the island，naming its central part a，or England.2.For nearly ______ years prior to the coming of the English，British had been a Roman province. In _____，the Rome withdrew their legions from Britain to protect herself against swarms of Teutonic invaders.3.The literature of early period falls naturally into teo divisions，and ____.The former represents the poetry which ____the Anglso-Saxons probably brought with them in the form of _____ ，the crude material out of which literature was slowly developed on English soil；the later represents the writings developed under the teaching of ______ .4._____can be justly termed England’s national epic and its hero _____---one of the national heros of the English people.5.The Song of Beowulf reflects events which took place on the ______ approximately at the beginning of the_____century，when the forefathers of the Jutes lived in the southern part of the _____ and maintained close relations with kindred tribes，e.g.with the ______ who lived on the other side of the straits.6.Among the early Anglo-Saxon poets we may mention______ who lived in the latter half of the ______ century and who wrote a poetic Paraphase of the Blible.7.____ is the first known religious poets of England. He is known as the father of English song.8.The didac tic poem “The Christ” was produced by ________.II. Choose the best answer for each blank.9.The most important work of _______ is the Anglo-Saxon Chronicles，which is regarded as the best monument of the old English prose.a. Alfred the Greatb. Caedmonc. Cynewulfd. Venerable Bede2. Who is the monster half-huamn who had mingled thirty warriors in The Song of Beowulf？a. Hrothgat.b. Heorot.c. Grendel.d. Beowulf.3. _____ is the first important religious poet in English Literature.a. Cynewulfb.Caedmonc. Shakepeare.d. Adam Bede4. The epic，The Song of Beowulf，represents the spirit of ______.a. monksb. romanticistsc. sentimentalistd. paganIII. Decide whether the following statements are true or false and write your answers in the brackets.1. （）The author of The Song of Beowulf is Cynewulf.2. （）The setting of The Song of Beowulf is in Scotland.3. （）Alfred the Great compiles The Anglo-Saxon Chronicles.4. （）Venerable Bede wrote The Ecclesiastical History of the English People.5. （）The author of Paraphase is Caedmon.IV. Define the liretary terms listed below.Alliteration Epic.V. Answer the following questions.1.What do you know about the Teutors.2.Please give a brief description of The Song of Boewulf.英国文学史及选读Chapter2发布人：圣才学习网发布日期：2010-08-16 17:31 共93人浏览[大] [中] [小]The Anglo-Norman PeriodI. Fill in the following blanks.1.In the year___，at the battle of ___，the ____ headed by William，Duke of Normandy，defeated the Anglo-Saxons.2.The literature which Normans brought to England is remarkable for its bright，____ tales of _______ and _______，in marked contrast with the ___ and ______ of Anglo-Saxon poetry.3.English literature is also a combination of ____and _____ elements.4.In the 14th century，the two most important writers are ___ and Chaucer.5.In the 15th century，there is only one important prose writer whose name is _____. He wrote an important work called Morte d’ Arthur.II. Define the leterature terms listed below.1.Canto2.legend3.Arthurian Legend.III. Read the excerpt of Sir Gawain and the Green Knight carefully，and then make a brief comment on it.IV. Answer the following questions.1.What is the consequence of the Norman Conquest？2.Make a brief survey of the middle English literature.英国文学史及选读Chapter3发布人：圣才学习网发布日期：2010-08-16 17:31 共68人浏览[大] [中] [小]Geoffrey ChaucerI. Fill in the following blanks.1.Chaucer’s masterpiece is _____，one of the most famous works in all literature.2.Chaucer created in The Canterbury Tales a strikingly brilliant and picturesque panorama of _______.3.There are various kinds of ballads _______，______，______，_____，and ______.4.Bishop ____ was among the first to take a literary interest in ballads.5.The name of the “jolly innkeeper” in The CanterburyTales is ______，who proposes that each pilgrim of the ____ should tell two tales on the way to Canterbury and two more on the way back.6.In contradistinction to the ______ verse of Anglo-Saxon poetry，Chaucer chose the metrical form which laid the foundation of the English _____ verse.II. Choose the best answer.1.Who is the “father of English poetry” and one of the greatest narrative poets of England？a. Christopher Marlowb. Geoffrey Chaucerc. W. Shakespeared. Alfred the Great2. Chaucer’s earlist work of any length is his “______” a transl ation of the French “Roman de la Rose” by Gaillaume de Lorris and Jean de Meung，which was a love allegory enjoying widespread popularity in the 13th and 14th centuries not only in France but throught Europe.a. Troilus and Criseydeb. A Red，Red Rosec. Romance of the Rosed. Piers the Plowman3. In his literary development，Chaucer was influenced by three literatures，which one is not true？a. French literature.b. Italian literaturec. English literatured. American literatureIII. Decide whether the following statements are true or false and write your answers in the brackets.1. （）The 32 pilgrims，according to Chaucer’s plan，was to exceed that of Baccoccio’s Decameron.2. （）The Prologue is a splendid masterpiece of Romantic portray，the first of its kind in the history of English literature.3. （）The Canterbury Tales is a vivid and brilliant reflection of 15th century in England.4. （）Chaucer’s poetry traces out a path to the literature of English Renaissance.IV. Define the leterary terms listed below.1.Romance.2.Fable.3.BalladV. Anwer the following question.1.What is the social significance of The Canterbury Tales ？英国文学史及选读Chapter4发布人：圣才学习网发布日期：2010-08-16 17:30 共66人浏览[大] [中] [小]The RenaissanceI. Complete each of the following statements with a proper word or phrase according to the textbook.1.Shakespeare’s first priginal play written in about 1590 was _________.2.Hamlet，Othello，King Lear，and _______ are generally regarded as Shakespeare’s four great tragedies.3.The Tragical History of Doct or Faustus is one of _______’s best known sonnets.4.Absolute monarchy in England reached its summit during the reign of ______.5.Bacon’s works may be divided into three classes，the ______，the _______，the _______ works.6.Together with the development of bourgeois relationships and formation of the English national state this period is marked by a flourishing of national culture known as the_________.7.Edmund Spenser was the author of the greatest epic poem of _______.II. Find out the author and his works.⑴The author and their works1. （）Thomas More a. Gorge Green2. （）Enmund Spenser b. Eupheus3. （）John Lyly c.The Fairy Queen4. （）Marlowe d. Utopia5. （）Robert Greene e. The Jew of Malta⑵The characters in the play1. （）Desdemona a. The Merchant of Venice2. （）Cordelia b. As you like it3. （）Juliet c.Hamlet4. （）Ophelia d. King Lear5. （）Portia e. Othello6. （）Rosalind f. Romeo and JulietIII. Define the leterary terms listed below.1.Renaissance2.sonnet3.Spenserian Stanza4.Humanism5.dramatic irony6.tragedy7.allusionIV. Answer the following questions.1.Give a summary about the English literature during the Renaissance period.2.What is the main idea of Hamlet？3.Give a brief introduction to Thomas More’s Utopia.4.Wh en were Shakespeare’s main tragedies written？what did he write about in his tragedies？英国文学史及选读Chapter5发布人：圣才学习网发布日期：2010-08-16 17:29 共40人浏览[大] [中] [小]Chapter Five The Period of Revolution and RestorationI. Complete each of the following statements with a proper word or phrase according to th etextbook.1.The 17th century was a period when ______ impeded the further development of capitalism in England and the ______ could no longer bear the sway of _______.2.England became a commomwealth under the leadership of _______.3.The Glorious Revolution in _____ meant three things the supremacy of ________，the beginning of _______，and the final truiumph of the principle of _______.4.Restoration created a literature of its own，that was often ______ and _______，but on the whole _______ and _______.5.The first thing to strik e the reader is Donne’s extraordinary _____ and penetrating_______. The next is the ______ which marks certain of the lighter poems and which represents a conscious reation from the extreme _______ of woman encouraged by the Petrachan tradition.6.Parad ise Lost presents the author’s view in an ______，_______ form. It is based on the _______legend of the imaginary progenitors of the human race-______，and _______，and involves God and his eternal adversary _____in its plot.7.Bunyan’s most important wo rk is _________，written in the old-fashioned，medieval form of ________ and _________.8.Christia has two objects，---to get rid of his ______，which holds the sins and fears of his life，and to make his way.II. Find out the work from column A and its content from column B.1. （）II Penseroso a. defense of the Revolution2. （）Lycidas b. Satan against God3. （）Comas c. about dear friend4. （）Areopagitica d. happiness5. （）Eikonolastes e. meditation6. （）Defense for the English People f. masque7. （）Paradise Lost g. attack on the censorship8. （）L’Allegro h. justifying the excutionIII.Define the leterature terms listed below.1 .Blank Verse2. Three Unities3. Conceit4. Stanza5. Elegy6 .Allegory7. GenreLiterary CriticismIV. Answer the following questions.1.What are the different aspects between the literature of Elizabeth period and that of the Revolution period？2.Give a brief analysis of Satan，the central figure in ParadiseLost.3.Why do people say Samson is Milton？4.In your opinion，why is “The Pilgrim’s P rogress” successful？英国文学史及选读Chapter6发布人：圣才学习网发布日期：2010-08-16 17:29 共34人浏览[大] [中] [小]The Age of Enlightenment EnglandI. Complete each of the following statements with a proper word or phrase according to th etextbook.1.The Revolution of 1688，which banished the last of the _____ kings，marks the end of the long struggle for political freedom in England.2.Another feature of the age was the rapid development of _________.3.It is simply for convenience that we study 18th century writings in three main divisions：the reign of so-called _____，the revival of _______ poetry，and the beginnings of the _______.4.The philosophy of the nlighteners，though ________ ________ and _________ in its essence，did not exclude senses，or sentiments，as a means of perception and learning.5.The most outstanding figure of English sentimentalism was ________.6.The Tarler and _______ _________ were Steele and Addison’s chief contribution to English literature.7.Robinson Crusoe is largely an ______ ________ ________ story，rather than the study of ______ _______ which Defoe probably intended it to be.8.Gulliver’s adventures begins with ______________，who are so small that Gulliver isa giant among them.9.The poem，which Addison named ______ _______，was hailed throughout England as a great work.10.In the essays of the 16th century，French writer ____ set the model for more familiar，personal and discursive discussion.11.Fielding’s laternovels are _______________，was inspired by the success of Ri chardson’s novel Pamela.12.As________，Goldsmith is among the best of the century.13. The greatest of _______ poets is Robert Burns.II. Match the theirs works in column A writers/genres with in column B.⑴1. （）The Deserted Village a. Thomas Gary2. （）The Village b. George Crabble3. （）Elegy Written in a Country Churchyard c. Oliver Goldsmith4. （）The Seasons d. James Thomson5. （）The Rape of the Lock e. William Blake6. （）The Chimney Sweeper f. Alexander Pope7. （） A Red，Red Rose g. Robert Burns⑵1. （）A Sentimental Journey a. Daniel Defoe2. （）The Vicar of Wakefield b. Jonathan Swift3. （）The School for Scandal c.John Bunyan4. （）The History of a Young Lady d. Horace Walpole5. （）Tom Jones e. Laurence Sterne6. （）The Adventures of Peregrine Pickle f. Oliver Goldsmith7. （）Robinson Crusoe g. Richard B. Sheridam8. （）Gulliver’s Tra vels h. Samuel Richardson9. （）The Castle of Otranto i. T. G. Smollet10.（）The Pilgrim’s Progress j. Fielding.⑶1. （）The Vicar of Wakefield a. essay2. （）She Stoops to Conquerb. poem3. （）The Citizen of the world c. novel4. （）The Deserted Village d. comedyIII.Define the leterature terms listed below.1.Enlightenment Movement2.Realistic Novel3.Gothic novel4.Heroic Couplet5.Mock Epic6.Bildungsroman7.Epitaph8.Farce9.Imagism10.RhymeIV. Answer the following questions.1.What is Pope’s position in English literature？2.What are the features of Sterne’s novels？3.What are the narrative festures of Gulliver’s Travel？4.What is Dr. Johnson’s comment on Addison’s prose？5.What is Fielding’s style？6.Why is Burn’s poetry important？英国文学史及选读Chapter7发布人：圣才学习网发布日期：2010-08-16 17:28 共27人浏览[大] [中] [小]The Romantic PeriodI. Fill in the following blanks.1.With the publication of William Wordworth’s _____ in Collaboration with S. T. Coleridge，________ began to bloom and found a firm place in the history of English literature.2.The most important and decisive factor in the develoment of literature is _____，English Romanticism was greatly influenced by the _______ and _______.3.The greatest historical novelist _____ was produced in the Romantic Age.4.Byron is chiefly known for his two long poems，one is Childe Harold’s Pilgrimage，the other is ________.5.Shelley’s poem _______ （1816），is vaguely autobiographical acount of a youn g poet’s unsuccessful attempt to recapture his envisional ideal.6.Ode to a Nightingale was written by _______.II. Decide whether the following statements are true or false.1. The Romantics emphasized the special qualities of each individual’s mind.2.The brilliant literary criticiam Biographis literaria is written by Samuel Johnson.III. Write the author of the following literary works.1. Song of Innocence2. The Prelude3. Kubla Khan4. Don Juan5. Prometheus Unbound6. Ode to the West Wind7. Ode on a Greciam Urn8. Pride and Prejudice9. Poor RelationsIV. Match the authors in column A with the works in columnB.1. Dante a. I Wandered Lonely as a Cloud2.Byron b. Ode to a Nightingale3. Wordsworth c. Gain4. Keats d. Prometheus Unbound5. Shelley e. Divine ComedyV. Define the following terms.1.Romanticism/doc/a410999246.htmlke poetsVI. Answer the following questions.1.How does Wordsworth define the poet？2.What kinds of stylistic devices are used in Ode to the West Wind？3.Co mment on Austen’s writing festures.英国文学史及选读Chapter7发布人：圣才学习网发布日期：2010-08-16 17:28 共27人浏览[大] [中] [小]The Romantic PeriodI. Fill in the following blanks.1.With the publication of William Wordworth’s _____ in Collaboration with S. T. Coleridge，________ began to bloom and found a firm place in the history of English literature.2.The most important and decisive factor in the develomentof literature is _____，English Romanticism was greatly influenced by the _______ and _______.3.The greatest historical novelist _____ was produced in the Romantic Age.4.Byron is chiefly known for his two long poems，one is Childe Harold’s Pilgrimage，the other is ________.5.Shelley’s poem _______ （1816），is vaguely autobiographical acount of a young poet’s unsuccessful attempt to recapture his envisional ideal.6.Ode to a Nightingale was written by _______.II. Decide whether the following statements are true or false.1. The Romantics emphasized the special qualities of each individual’s mind.2.The brilliant literary criticiam Biographis literaria is written by Samuel Johnson.III. Write the author of the following literary works.1. Song of Innocence2. The Prelude3. Kubla Khan4. Don Juan5. Prometheus Unbound6. Ode to the West Wind7. Ode on a Greciam Urn8. Pride and Prejudice9. Poor RelationsIV. Match the authors in column A with the works in columnB.1. Dante a. I Wandered Lonely as a Cloud2.Byron b. Ode to a Nightingale3. Wordsworth c. Gain4. Keats d. Prometheus Unbound5. Shelley e. Divine ComedyV. Define the following terms.1.Romanticism/doc/a410999246.htmlke poetsVI. Answer the following questions.1.How does Wordsworth define the poet？2.What kinds of stylistic devices are used in Ode to the West Wind？/doc/a410999246.htmlment on Austen’s writing festures.英国文学史及选读Chapter9发布人：圣才学习网发布日期：2010-08-16 17:26 共37人浏览[大] [中] [小]The 20TH Century LiteratureI. Fill in the following blanks.1.Those “novels of character and enviorement” by T homas Hardy are the most representative of him as both a _______ and a critical realist writer.2.The trilogy “The Forsyte Saga” consists of The Man of Propert y，In Chancery and_________./doc/a410999246.htmlwrence first novel，_________________，was received with respect.4.Virginia Woolf’s novel ________________，published in 1925，made her reputation as an important psychological writer.5._________is the m ost outstanding stream of consciousnessnovelist.II. Define the literary terms.1.Imagism2.ModernismIII. Find the relevant match from column B for each item in column A.1. James Joyce a. Neo-classicism2. Ezra Pound b. An active romantic3. William Wordsworth c. Humanism4. Oscar Wilde d. Transcendantalism5. Walter Scott e. A radical enlightenner6. Alezander Pope f. Imagism7. Johanthan Swift g. Aestheticism8. Percy Bysshe Shelley h. A lake Poet9. William Shakespeare i. Stream of consciousness10. Henry，David Thoreau j. A historical novelistIV. Give a brief comment on the c haracteristic of Hardy’s novels.。

论索尔·贝娄短篇小说中叙事伦理

The Narrative Ethics On Saul Bellow’s Short StoriesCandidate Gao DaoSupervisor Prof.Ji ShuiheCollege Literature and Journalism College Program Comparative Literature and World Literature Specialization Comparative Reasearch on Chinese-Western Theory and Literary Criticism Degree Master of Literature University Xiangtan UniversityDate April 10th, 2010湘潭大学学位论文原创性声明本人郑重声明：所呈交的论文是本人在导师的指导下独立进行研究所取得的研究成果。

除了文中特别加以标注引用的内容外，本论文不包含任何其他个人或集体已经发表或撰写的成果作品。

对本文的研究做出重要贡献的个人和集体，均已在文中以明确方式标明。

本人完全意识到本声明的法律后果由本人承担。

作者签名：日期：年月日学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，同意学校保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。

本人授权湘潭大学可以将本学位论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文。

涉密论文按学校规定处理。

作者签名：日期：年月日导师签名：日期：年月日摘要贝娄一生创作颇丰，就其短篇小说的创作而言，其作品中所蕴含着的强烈的伦理道德性是其主要的特点之一，创作中所采用的多视角、人称变换、情境叙事、拼贴式叙事结构等也使作品在叙事上具备了丰富的可言说性。

由于深受犹太文化浸染及对犹太人的深挚情感，贝娄作品的思想核心仍是鲜明的犹太性，同时以犹太教伦理意识中所强调的公义、赎罪、上帝的慈爱等为依托，面对现代人所感到的孤独与迷失，贝娄通过小说所倡导的仍是一种积极调整心态、勇于承担责任的生活方式，对绝望虚无的人生态度进行否定；作为深受人文主义传统影响的贝娄，通过作品提倡以回归传统德性来疗治虚无感和荒谬感的现代病，这种回归不单具有社会伦理意义，同时也寄托着作者的审美情思；贝娄作品的叙事主体、叙事结构、叙事时空观、情境叙事，艺术性地传达了其伦理诉求。

多元与描写翻译学派教材

Maintaining a primary position
• three circumstances 1 when a literature is young or in the process of being established当多元系统尚未定型，或文学的发展尚处于正在建立阶段 2 when a literature or peripheral or weak or both该文学在一组相关的文学体系中处于“边缘”或“弱势”的阶段 3 when a literature is experiencing a crisis or turing point该文学出现转折点、危机或文学真空阶段。
Principles ----can be used to describe both relations within literary system and extraliterary system. Hfocus primarily on literary.
He prescribes a translation model that transcends time. His work is highly innovative by looking at actual translations within the larger sociological context.翻译活动实际上是由译入语文化里的各个系统所决定的。既然如此，翻译就不再是个性质和界限已经确定就不再变化的东西，而是依赖于一定文化系统中各种关系的一种活动。
His early work is important to translation theory.
He gives attention to the role of translation within a literary system.基本确定了翻译文学跟译入语文化文学在不同情况下的不同关系

河水污染的解决方法英语作文

河水污染的解决方法英语作文英文回答：Addressing River Water Pollution: Innovative Approaches and Sustainable Solutions.River water pollution is a global environmental crisis that threatens human health, aquatic ecosystems, and economic development. It is imperative to implement innovative approaches and sustainable solutions to mitigate this persistent issue.One promising strategy is bioremediation, which involves harnessing the natural capabilities of microorganisms, plants, and other biological agents to break down and remove pollutants. Phytoremediation, a specific form of bioremediation, utilizes plants to absorb and metabolize contaminants from water bodies. These plants can act as natural filters, removing heavy metals, pesticides, and other toxic substances.Advanced oxidation processes (AOPs) represent another effective approach. AOPs generate hydroxyl radicals, potent oxidants that can degrade organic pollutants into harmless byproducts. They can be applied in various forms, including photocatalysis, ozonation, and Fenton's reaction.Membrane technologies offer another promising solution. Microfiltration, ultrafiltration, and reverse osmosis can effectively remove particles, pathogens, and dissolved substances from water. These technologies have high efficiency and can be integrated into existing wastewater treatment systems.Electrocoagulation is an emerging technology that utilizes electric currents to destabilize pollutants and induce their aggregation. The resultant flocs can be easily removed by sedimentation or flotation. It has proven effective in removing heavy metals, dyes, and other pollutants from water.Green infrastructure solutions, such as constructedwetlands and rain gardens, mimic natural ecosystems and provide a sustainable approach to water treatment. These systems utilize vegetation, soil, and natural processes to filter and clean pollutants from water. They can be integrated into urban areas and provide additional benefits, such as flood control and wildlife habitat.Citizen science and community engagement can play a crucial role in combating river water pollution. Empowering local communities to monitor, report, and advocate forclean water can create awareness, foster stewardship, and drive policy changes.By combining innovative technologies, implementing sustainable solutions, and engaging communities, we can effectively address river water pollution and protect these vital ecosystems for future generations.中文回答：解决河流污染问题，创新方法和可持续对策。

河流污染问题及解决措施英语作文

河流污染问题及解决措施英语作文全文共3篇示例，供读者参考篇1River pollution is a pressing environmental issue that poses serious threats to ecosystems, public health, and the economy. Industrial waste, agricultural runoff, and untreated sewage are among the primary sources of pollution that contaminate rivers around the world. The consequences of river pollution arefar-reaching and include waterborne diseases, loss of biodiversity, and compromised water quality for drinking, irrigation, and recreational purposes.To address the problem of river pollution, it is essential to implement a multi-faceted approach that involves regulations, technology, and public awareness. Governments play a crucial role in setting and enforcing strict environmental laws and regulations that limit the discharge of pollutants into rivers. By holding industries accountable for their waste disposal practices and implementing fines for non-compliance, governments can incentivize businesses to adopt cleaner production methods and invest in pollution control measures.In addition to regulatory measures, technological solutions can also help mitigate river pollution. Advanced wastewater treatment systems, such as membrane filtration and ultraviolet disinfection, can effectively remove contaminants from sewage before it is discharged into rivers. Similarly, innovative techniques for treating industrial wastewater, such as bioremediation and phytoremediation, can help reduce the impact of industrial pollution on river ecosystems.Furthermore, public awareness and community engagement are essential components of any successful river pollution prevention strategy. By educating the public about the importance of clean water and the impact of pollution on rivers, individuals can make informed choices that help protect water resources. Community-based initiatives, such as river clean-up events and monitoring programs, can also empower local residents to take action against river pollution in their own neighborhoods.In conclusion, the problem of river pollution is a complex and urgent issue that requires collective action from governments, industries, and individuals. By implementing stringent regulations, adopting innovative technologies, and fostering public awareness, we can work together to safeguardour rivers and ensure clean water for current and future generations. Only by taking decisive steps to address river pollution can we protect the health and vitality of these vital natural resources.篇2River pollution is a serious environmental issue that affects both the ecosystem and human health. The pollution of rivers is primarily caused by industrial waste, agricultural runoff, and untreated sewage being discharged into water bodies. This pollution has detrimental effects on aquatic life, water quality, and the health of people who rely on these rivers for drinking water and livelihoods.One of the major sources of river pollution is industrial waste. Industries release a variety of harmful chemicals and pollutants into rivers, including heavy metals, pesticides, and solvents. These pollutants can have toxic effects on aquatic life, disrupting ecosystems and harming fish, birds, and other wildlife. Industrial waste can also contaminate water sources used for drinking and agriculture, posing a risk to human health.Agricultural runoff is another significant contributor to river pollution. Pesticides, fertilizers, and animal waste from farms canwash into rivers and streams, causing nutrient pollution and algal blooms. These blooms can deplete oxygen levels in the water, leading to the death of fish and other aquatic organisms. Agricultural runoff can also introduce pathogens and bacteria into water sources, increasing the risk of waterborne diseases.Untreated sewage is a major source of river pollution in many parts of the world. Inadequate sanitation systems and wastewater treatment facilities can result in raw sewage being discharged directly into rivers and streams. This not only contaminates water sources with harmful bacteria and pathogens but also contributes to nutrient pollution and eutrophication. The high levels of nutrients in sewage can lead to excessive algae growth, further impairing water quality and aquatic ecosystems.To address the problem of river pollution, various strategies and solutions can be implemented. One key measure is the enforcement of strict regulations and pollution control measures for industries and agricultural operations. Industries should be required to treat their wastewater before discharging it into rivers, and farms should adopt sustainable practices to reduce the use of chemicals and minimize runoff.Investing in wastewater treatment infrastructure is essential for preventing untreated sewage from polluting rivers. Governments should prioritize the construction of treatment plants and sewage systems to ensure that all wastewater is properly treated before being released into water bodies. Public awareness and education campaigns can also help promote water conservation and pollution prevention practices among communities living near rivers.Additionally, the restoration and protection of riparian zones can help improve water quality and mitigate the impacts of pollution on rivers. Planting trees and vegetation along riverbanks can help filter out pollutants, reduce erosion, and provide habitat for wildlife. Creating buffer zones and wetlands can also help absorb excess nutrients and improve water quality downstream.In conclusion, river pollution is a significant environmental issue that requires urgent action to protect water resources and ecosystems. By addressing the sources of pollution, implementing pollution control measures, and investing in sustainable water management practices, we can work towards restoring and preserving the health of our rivers for future generations. It is essential that governments, industries, andcommunities work together to tackle river pollution and ensure clean and safe water for all.篇3River pollution is a serious environmental issue that affects both aquatic life and human health. Industrial activities, agriculture, and improper waste disposal are major contributors to river pollution. The presence of pollutants such as chemicals, heavy metals, and sewage in rivers can lead to a decline in water quality, loss of biodiversity, and health risks for those who rely on the river for drinking water or recreation.To address the problem of river pollution, various measures can be taken at different levels. One of the key strategies is to enforce strict regulations and laws to control the discharge of pollutants into rivers. Industries should be required to treat their wastewater before releasing it into water bodies, and agricultural practices should be regulated to minimize the use of harmful fertilizers and pesticides that can leach into rivers.Another important solution is to promote sustainable practices that reduce pollution at the source. This can include investing in cleaner production technologies, implementingwatershed management strategies, and promoting the use of eco-friendly alternatives to harmful chemicals.In addition, public awareness and education play a crucial role in tackling river pollution. People need to be informed about the impacts of pollution on rivers and the importance of protecting water resources. Community clean-up initiatives, campaigns to reduce plastic waste, and educational programs in schools can all help raise awareness and foster a sense of responsibility towards the environment.Furthermore, collaboration and coordination among stakeholders are essential for effective river pollution control. Governments, businesses, non-governmental organizations, and local communities need to work together to develop and implement comprehensive pollution prevention and control programs. Cooperation can help mobilize resources, share knowledge and expertise, and ensure that efforts are coordinated and integrated for maximum impact.Ultimately, addressing river pollution requires amulti-faceted approach that combines regulatory measures, sustainable practices, public awareness, and collaboration among stakeholders. By taking concrete actions to reducepollution and protect rivers, we can ensure the health and sustainability of our water resources for future generations.。

文学建议英语作文初一

文学建议英语作文初一Title: Literary Recommendations for English Composition in Grade Nine。

Literature plays a crucial role in shaping our perspectives, enhancing our language skills, and fostering empathy. As a first-year student exploring the realm of English composition, it's pivotal to engage with a diverse range of literary works. Here are some recommendations that can enrich your understanding and inspire your writing journey:1. "To Kill a Mockingbird" by Harper Lee:This timeless classic delves into profound themes such as racial injustice, moral growth, and empathy. Through the eyes of Scout Finch, readers witness the complexities of human nature and the importance of standing up for what is right, even in the face of adversity. Exploring characters like Atticus Finch can provideinsights into moral integrity and the power of perspective, which you can incorporate into your compositions to add depth and resonance.2. "The Catcher in the Rye" by J.D. Salinger:Holden Caulfield's rebellious voice and existential angst resonate with many young readers. This coming-of-age novel captures the struggles of adolescence and the quest for authenticity in a conformist society. Delving into themes of alienation, identity, and innocence lost, "The Catcher in the Rye" offers rich material for introspective writing and character analysis. You can explore the complexities of teenage emotions and societal pressures in your compositions, drawing parallels to Holden's journey.3. "1984" by George Orwell:Orwell's dystopian masterpiece paints a chilling portrait of a totalitarian regime where individuality is suppressed, and truth is manipulated. Through the protagonist Winston Smith, readers confront the dangers ofunchecked authority and the erosion of freedom. "1984" prompts reflection on surveillance, propaganda, and the fragility of democracy, offering ample fodder for persuasive essays and speculative fiction. You can analyze Orwell's depiction of power dynamics and explore themes of resistance and resilience in your compositions.4. "The Giver" by Lois Lowry:Set in a seemingly utopian society where emotions are suppressed and choices are limited, "The Giver" follows Jonas as he discovers the true cost of conformity. Lowry's novel invites readers to ponder the value of individuality, free will, and human connection. By examining Jonas's journey towards self-awareness and autonomy, you can explore themes of personal agency and the pursuit of truth in your compositions. Consider how the absence of choice impacts characters' lives and extrapolate these insights into real-world contexts.5. "Lord of the Flies" by William Golding:Golding's allegorical tale explores the descent into savagery when a group of boys is stranded on a deserted island. As they grapple with power struggles and primal instincts, readers confront the darker aspects of human nature and the fragility of civilization. "Lord of the Flies" offers fertile ground for analyzing symbolism, character development, and societal dynamics. You can draw parallels between the characters' behavior and real-world events, reflecting on the nature of power, conflict resolution, and the thin veneer of civilization in your compositions.Incorporating insights from these literary works into your English compositions can elevate your writing by infusing it with depth, nuance, and thematic richness. By exploring diverse perspectives and grappling with universal truths, you'll not only hone your language skills but also cultivate empathy and critical thinking. So, dive into these literary treasures and let them inspire your creative journey in English composition.。

Progress in the Pursuit of Therapeutic

Progress in the Pursuit of TherapeuticAdenosine ReceptorAntagonistsStefano Moro,1Zhan-Guo Gao,2Kenneth A.Jacobson,2Giampiero Spalluto31Molecular Modeling Section,Dipartimento di Scienze Farmaceutiche,Universita`di Padova,Via Marzolo5,I-35131Padova,Italy2Molecular Recognition Section,Laboratory of Bioorganic Chemistry,National Institute of Diabetes and Digestive and Kidney Diseases,National Institutes of Health,Bethesda,Maryland208923Dipartimento di Scienze Farmaceutiche,Universita`degli Studi diTrieste,Piazzale Europa1,I-34127Trieste,ItalyPublished online27December2005in Wiley InterScience().DOI10.1002/med.20048!Abstract:Ever since the discovery of the hypotensive and bradycardiac effects of adenosine,adenosine receptors continue to represent promising drug targets.First,this is due to the fact thatthe receptors are expressed in a large variety of tissues.In particular,the actions of adenosine(ormethylxanthine antagonists)in the central nervous system,in the circulation,on immune cells,andon other tissues can be beneﬁcial in certain disorders.Second,there exists a large number ofligands,which have been generated by introducing several modiﬁcations in the structure of the leadcompounds(adenosine and methylxanthine),some of them highly speciﬁc.Four adenosinereceptor subtypes(A1,A2A,A2B,and A3)have been cloned and pharmacologically characterized,all of which are G protein-coupled receptors.Adenosine receptors can be distinguished accordingto their preferred mechanism of signal transduction:A1and A3receptors interact with pertussistoxin-sensitive G proteins of the G i and G o family;the canonical signaling mechanism of the A2Aand of the A2B receptors is stimulation of adenylyl cyclase via G s proteins.In addition to thecoupling to adenylyl cyclase,all four subtypes may positively couple to phospholipase C viadifferent G protein subunits.The development of new ligands,in particular,potent and selectiveantagonists,for all subtypes of adenosine receptors has so far been directed by traditional medicinalchemistry.The availability of genetic information promises to facilitate understanding of the drug–receptor interaction leading to the rational design of a potentially therapeutically important class ofdrugs.Moreover,molecular modeling may further rationalize observed interactions between thereceptors and their ligands.In this review,we will summarize the most relevant progress indeveloping new therapeutic adenosine receptor antagonists.ß2005Wiley Periodicals,Inc.Med Res Rev,26No.2,131–159,2006Key words:G protein-coupled receptor;adenosine receptor;antagonistsContract grant sponsor:Universityof Padova;Contract grant sponsor:Italian Ministry for Universityand Research,Rome,Italy Correspondence to:Stefano Moro,Molecular Modeling Section,Dipartimento di Scienze Farmaceutiche,Universita di Padova,Via Marzolo5,I-35131Padova,Italy.E-mail:stefano.moro@unipd.itMedicinal Research Reviews,Vol.26,No.2,131^159,2006ß2005Wiley Periodicals,Inc.132*MORO ET AL.1.I N T R O D U C T I O NThe stimulation of cell surface adenosine receptors(ARs)is largely responsible for the broad variety of effects produced by adenosine throughout several organ systems.Based on the widespread and frequently beneﬁcial effects,attributed to the accumulation of endogenously released adenosine,it has long been considered that regulation of ARs has substantial therapeutic potential.Incidentally, much recent focus has been on the cardioprotective1,2and neuroprotective3,4effects associated with AR activation during periods of cardiac and cerebral ischemia,respectively.On the other hand,it has been proposed recently that antagonists of distinct AR subtypes may be used in the treatment of asthma5,6or certain neurological diseases such as Parkinson’s disease.6,7Comprehensive reviews of the physiological roles of ARs and their potential as clinical targets in a variety of disease states have been published.6–11ARs are members of the superfamily of G protein-coupled receptors(GPCRs),with four subtypes currently recognized,the A1AR,A2A AR,A2B AR,and A3AR.12With the exception of the A3AR,the existence of AR subtypes in various tissues had been appreciated prior to their cloning as a result of pharmacological characterization.12The cloning of the four AR subtypes has allowed for signiﬁcant progresses to be made in the understanding of several facets of AR activity at a molecular level.A schematic representation of AR signaling pathways shown in Figure1.11Considering the overall protein structure,ARs display the topology typical of GPCRs.Many features of GPCR structure and function have been reviewed recently.12–15Here we will highlight some fundamental features that may expand upon the classical view of GPCR structure and function. Sequence comparison between the different GPCRs revealed the existence of different receptor families sharing no sequence similarity even if speciﬁcﬁngerprints exist in all GPCR classes. However,all these receptors have in common a central core domain consisting of seven transmembrane helices(TM1-7),with each TM composed of20–27amino acids,connected by three intracellular(IL1,IL2,and IL3)and three extracellular(EL1,EL2,and EL3)loops.Two cysteine residues(one in TM3and one in EL2),which are conserved in most GPCRs,form a disulﬁde link which is possibly crucial for the packing and for the stabilization of a restricted number of conformations of these seven TMs.Aside from sequence variations,GPCRs differ in the length and function of their N-terminal extracellular domain,their C-terminal intracellular domain,and their intracellular loops.Each of these domains provides very speciﬁc properties to these receptor proteins.ARs,Particularly,consensus sites for N-linked glycosylation exist on the extracellular regions of Array Figure1.Signal transduction pathways associated with the activation of the human adenosine receptors.Abbreviations:a,a-subunit of G protein;bg,bg-subunits of G protein;A TP,adenosine triphosphate;cAMP,cyclic adenosine monophosphate;DAG, diacylglycerol;G i,G i family of G proteins;G s,G s family of G proteins;G o,G o family of G proteins;G q,G q family of G proteins;IP3, inositol(1,4,5)-trisphosphate;P,phosphate moiety;PKC,protein kinase C;PL C,phospholipase C.although the precise location of the sites for this post-translational modiﬁcation varies amongst the AR subtypes.16–19The carboxyl-terminal tails of the A 1A R,A 2B AR,and A 3AR,but not A 2A AR,possess a conserved cysteine residue that may putatively serve as a site for receptor palmitoylation and permit the formation of a fourth intracellular loop.However,site-directed mutagenesis of this residue has not been performed for any AR subtype,and no role for putative AR palmitoylation has been described.The A 1AR,A 2B AR,and A 3AR are very similar in regard to the number of amino acids composing their primary structure,and in general,these AR subtypes are among the smaller members of the GPCR family.For example,the human homologs of the A 1AR,A 2B AR,and A 3AR consist of 326,328,and 318amino acid residues,respectively.20–22Conversely,the human A 2A AR is composed of 409amino acids.23All cloned species homologs of the A 2A AR are of similar mass,and this relatively large size is manifested in the carboxyl-terminal tail of the receptor,which is much longer than that of the other AR subtypes.It should be noted that the size of ARs deduced from their primary amino acid structure frequently is not consistent with the mass estimated by polyacrylamide gel electrophoresis of the expressed proteins.The aforementioned post-translational glycosylation of ARs,which may vary in a cell type-dependent fashion,likely accounts for these discrepancies.The human A 1AR and human A 3AR display ca 49%overall sequence identity at the amino acid level,while the human A 2A AR and human A 2B AR are 45%identical.A general topology of all four receptor subtypes are shown in Figure 2.Indeed,for all GPCRs,the identiﬁcation of discrete receptor regions,or even single amino acids that are critical for ligand recognition and are responsible for discerning between agonist and antagonist ligands,has been an area of extensive investigation.11,24–27In addition to abasic Figure 2.General topology of all adenosine receptors obtained using a rhodopsin-based homology modeling (modified from Moto et al.11).THERAPEUTIC ADENOSINE RECEPTOR ANT AGONISTS *133134*MORO ET AL.understanding of receptor activation,it has been hoped that a delineation of ligand–receptor interaction at a molecular level may provide the basis for rational drug design.11,24–27As summarized below,both TMs and extracellular regions of ARs have been implicated as playing a role in the formation of the ligand-binding pocket.11,24–27Key amino acids identiﬁed via mutagenesis studies as contributing to the ligand-binding properties of the ARs are brieﬂy summarized in Table I.Site-directed mutagenesis studies in parallel with different molecular modeling approaches have been recently used as powerful strategy to design potent and selective GPCR ligand.11,36–39Of course,the evolution of theﬁeld of computer-aided design of ligands(both agonists and antagonists) for GPCRs,including adenosine receptors,has depended on the availability of suitable molecular receptor templates.In fact,due to technical difﬁculties,which complicate experimental X-ray diffraction and NMR structure determination of GPCRs,the3D structure of most GPCRs is still unknown.The only known GPCR structure,a2.8A˚resolution structure of rhodopsin,was published only recently by Palczewski and collaborators.40However,a structure-based approach to GPCR drug discovery in the absence,but probably also in the presence,of the real structures requires a multidisciplinary approach,where molecular models represent a structural context to efﬁciently integrate experimental data and inferences derived from molecular biological,biophysical, bioinformatic,pharmacological and organic chemical methods.Although not always achievable, the success of a synergistic effect among these disciplines is highly dependent on the experimental design.Synergy is best achieved when mutations are structurally interpretable,structural hypotheses are experimentally testable,ligands are well characterized pharmacologically,and the necessary chemical modiﬁcations of the ligands are feasible.11In recent decades,numerous medicinal chemistry groups have made intense efforts in searching for ideal ligands for these receptor subtypes.9–11,41–45In particular,the search for selective antagonists held greater appeal than selective agonists,not only for their potential therapeutic applications but also considering the fact that antagonists are preferred molecular probes for pharmacological characterization of receptors.Considering all of these aspects,the search for potent and selective adenosine receptor antagonists has been one of the most highly investigated areas in medicinal chemistry in recent years.It should be emphasized that for all the receptor subtypes the alkylxanthines (e.g.,theophylline,caffeine),which are natural antagonists for the adenosine receptors,have represented the starting point for the discovery of potent and selective antagonists.41–45Following multiple modiﬁcations of the xanthine nucleus,various potent and selective antagonists have been found.Nevertheless,xanthine derivatives have several physico-chemical limitations,including low water solubility.For this reason,several research groups have focused on compounds having a non-xanthine structure for improving the water solubility and consequently bioavailability.41–45 The purpose of this review is to summarize the most recent developments made in theﬁeld of adenosine receptor antagonists,which for all classes could be subdivided into two large families:(i)xanthine derivatives;(ii)polyheterocyclic derivatives.2.A1A D E N O S I N E R E C E P T O R A N T A G O N I S T SThe A1AR could be considered the best-characterized member of the adenosine receptor family. Several antagonists are currently under clinical investigations,and are recently reviewed.10,41–43 A.Xanthine DerivativesA large number of modiﬁcations on the xanthine core at the1,3,and8positions led to the discovery of 8-cyclopentyl-1,3-dipropylxanthine(DPCPX,1)which was highly potent and selective at the adenosine A1AR in a rat model,46while at the human A1AR it was10-fold less potent with a consequent reduction of selectivity versus the other receptor subtypes.Also,DPCPX displays considerable afﬁnity at the human A2B AR.47For these reasons the search for a truly selective A1ARTHERAPEUTIC ADENOSINE RECEPTOR ANT AGONISTS*135 adenosine receptor antagonist in the human model represented a new appealing goal to be achieved (Fig.3).In addition to DPCPX,other substituted xanthines have been proposed as A1AR antagonists,in particular,by introducing chiral substituents to demonstrate the importance of the stereochemistry,or by insertion of polar moieties.The introduction at the8-position on the1,3-dipropylxanthine nucleus of a[2-(5,6-epoxy)norbornyl]moiety led to the discovery of BG-9719(2)which was highly potent and selective at the A1AR in a human model.48A small stereochemical effect on the afﬁnity was present with this compound,such that the R-isomer was twofold less potent(K i hA1¼0.80nM)than the S-isomer(Fig.3).Recently,aﬂuorescent derivative of the xanthine amine functionalized congener(XAC)49was shown to be useful for visualizing the A1AR in small areas of cell membranes usingﬂuorescence correlation spectroscopy.50B.Polyheterocyclic DerivativesNumerous classes of heterocyclic derivatives were shown to bind to the A1AR.Among theﬁrst such derivatives were the1H-imidazo[4,5-c]quinolin-4-amines,which were synthesized based on a prediction from early ligand modeling.51Most of these derivatives could be considered an extension of the xanthine structure.More recently,some synthetic triazolo-purinones(3,4),clearly derived as tricyclic extensions of the xanthine nucleus,showed very promising afﬁnity at the A1AR subtype with signiﬁcant degree of selectivity versus the A2A AR subtype(Fig.4).52Another class of A1AR antagonists is represented by3-aryl-[1,2,4]triazino[4,3-a]-benzimida-zol(10H)-4-one derivatives.In particular,compound5displayed high afﬁnity at the bovine A1AR and signiﬁcant selectivity in comparison to the A2A AR and A3AR subtypes(Fig.4).53A related A1AR antagonist could be considered the triazolo-quinoxaline6which displays high potency and good selectivity(Fig.4).54Isosteres of6,such as pyrazolo-quinolines or imidazo-quinoxalines have been also reported as A1AR antagonists.Although the afﬁnity at A1AR was in the nanomolar range,none of the reported compounds were found to be highly selective.55,56A series of non-xanthine heterocycles displaying high potency at A1AR and selectivity versus all the other subtypes is represented by7-deaza-adenines.One particular derivative7(APEPI)proved to be highly potent and selective(Fig.4).The A1AR afﬁnity is prevalently due to the R-enantiomer. Many other modiﬁcations have been made on this nucleus(e.g.,replacement of phenyl ring at the 2position or structure simpliﬁcation to an indole nucleus),but none of these variations improved both afﬁnity and selectivity.56,57Very simpliﬁed heterocyclic derivatives as adenosine receptor antagonists are represented by thiazole and thiadiazole derivatives(Fig.5).In particular,thiadiazole8(LUF5437)has been considered the starting point for this new class of compounds.58In fact,complete hydrogenation of phenyl ring led to derivative9(LUF5472),which was less potent at the A1AR but more selective. Replacement of the thiadiazole nucleus with a thiazole moiety seemed to be well tolerated at the A1 receptor.58,59Another class of simpliﬁed analogs structurally related to the xanthine core consists of derivatives of the pyrazolo[1,5-a]pyridine pound10(FK453)represents the lead compound of this series showing favorable afﬁnity and selectivity for the A1AR compared to the A2A AR(Fig.5).Various modiﬁcations have been performed on this nucleus but when acryloyl amide was constrained into a pyridazinone nucleus and nitrogen was substituted with an isobutyryl moiety(compound11)a signiﬁcant increase of potency and selectivity was obtained(Fig.5).60–62 Also,a naphthyridine nucleus has been investigated for A1AR antagonists.In a naphthyridine series,compound12proved to be a promising antagonist displaying afﬁnity in a sub-nanomolar range and high levels of selectivity in a bovine model,while unfortunately in human the compound dramatically lost potency and consequently selectivity.63,64T a b l e I .A m i n o A c i d s o f A R s I m p l i c a t e d i n L i g a n d B i n d i ng136*MORO ET AL.1A m i n o a c i d s r e p r e s e n t e d i n s i n g l e -l e t t e r c o d e w i t h p o s i t i o n n u m b e r s h o w n .T h e f i r s t a m i n o a c i d i s t h a t o f t h e w i l d -t y p e r e c e p t o r ,w i t h t h e s e c o n d r e s i d u e t h a t u s e d f o r s u b s t i t u t i o n .R e f e r e n c e s a r e c o l l e c t e d i n s i d e s q u a r e b r a c k e t s .2A l l s t u d i e s r e f e r r i n g A 2A A R a n d A 3A R e x a m i n e d t h e h u m a n c l o n e d r e c e p t o r s .THERAPEUTIC ADENOSINE RECEPTOR ANT AGONISTS *137Very recently,IJzerman and coworkers synthesized a large number of pyrimidine derivatives designed with the help of molecular modeling.This study permitted to identify the compound13that was potent and selective as a human A1AR antagonist(Fig.5).65As clearly described,chemically diverse classes of compounds have been identiﬁed as A1AR antagonists.Nevertheless,considering that many have not yet been examined at all four adenosine receptor subtypes and the species differences are evident,most of these synthetic compounds should be reexamined in a human model for better understanding and for consideration as clinical candidates.C.Biological Actions of A1Adenosine Receptor AntagonistsPeripheral applications envisioned for A1receptor antagonists include kidney protection and cardiac anti-arrhythmic agents.42,43Since caffeine is best known for its stimulant activity in the central nervous system,adenosine antagonists of the A1receptor and other subtypes have been of interest in cognitive disorders.A novel,potent,and selective adenosine A1receptor antagonist FR194921exerts both cognitive-enhancing and anxiolytic activity,suggesting the therapeutic potential of such compounds for dementia and anxiety disorders.663.A2A A D E N O S I N E R E C E P T O R A N T A G O N I S T SBoth xanthines and non-xanthines have been developed as selective A2A AR antagonists.A2A AR antagonists proved to be attractive for the treatment of several diseases of the central nervous system, such as motor dysfunctions,due to the clearly demonstrated interaction between A2A AR and D2 dopamine receptors(both at the protein and second messenger levels)in the basal ganglia.67For this reason,A2A AR antagonists could be considered potential drugs for the treatment of neurodegen-erative disorders such as Parkinson’s disease.A.Xanthine DerivativesTheﬁrst xanthine analog,which displayed good potency at the A2A AR subtype(100nM)and signiﬁcant selectivity in comparison to the A1AR(45-fold)was the8-unsubstituted1-propargylxanthine(14)(Fig.6).68Starting from this observation,a program to screen various1-,3-,8-substituted xanthines led to the discovery of theﬁrst very potent and selective A2A AR antagonist,1,3-dipropyl-7-methyl-8-(3, 4-dimethoxystyryl)xanthine(KF17837,15),which proved to be potent in the nanomolar range at the A2A AR subtype(1nM)and signiﬁcantly selective in comparison to A1AR(62-fold)(Fig.3).69,70In adetailed SAR study on this class of compounds,the 3-chlorostyrylcaffeine (CSC,16)was identiﬁed as being less potent than 15at the A 2A AR (54nM)but with an increased selectivity in comparison to the A 1AR subtype (560-fold).71Two major problems have limited the use of these xanthine derivatives as pharmacological tools for studying the A 2A AR subtype:(a)the low water solubility;72(b)the rapid photoisomerization which they undergo when exposed to daylight in dilute solution.73It should be noted that this isomerization process is not relevant when styrylxanthines are administered orally as solid substances.In an attempt to avoid this problem,the styryl moiety has been replaced with different functional groups (e.g.,triple bond,cyclopropyl,or diazo group)or constrained structure.However,none of this isosteric substitutions has led to an improvement in the pharmacological proﬁle,but rather in many cases to a complete loss of afﬁnity.68,74Instead,the introduction of a propargyl at the 1-position in combination with the 8-styryl group by Mu¨ller and coworkers seemed to increase afﬁnity at the A 2A AR subtypes with the retention of selectivity.These studies led to the discovery of the BS-DMPX (3,7-dimethyl-1-propargyl-8-(3-bromostyryl)xanthine 17,which could be considered a lead compound of a new series.75However,at the 3and 7positions,methyl substitution seemed to be desirable for achieving both afﬁnity and selectivity at the A 2A AR subtype (Fig.6).76–78Regarding the substitutions at the 8-position,it has been clearly demonstrated that an aromatic ring attached to an ethenyl group is a fundamental requirement for both afﬁnity and selectivity at the A 2A AR.77,79For the improvement of water solubility of styryl xanthines,two different approaches have been utilized:(a)introduction of polar groups on the phenyl ring;(b)preparation of phosphate pro-drugs.The introduction of a sulfonate group on the phenyl ring of styryl moiety produces a signiﬁcant reduction of afﬁnity (20-to 30-fold)at the A 2A AR but with retention of selectivity.80Figure 4.Structures and binding affinities of non-xanthine adenosine A 1AR antagonists.THERAPEUTIC ADENOSINE RECEPTOR ANT AGONISTS *139More interesting results have been obtained using phosphate ester pro-drugs.In fact,the pro-drug18,which was stable in aqueous solution but readily cleaved by phosphatases to liberate MSX-2 (3-(3-hydroxypropyl)-8-(3-methoxystyryl)-1-propargylxanthine,showed a very high afﬁnity and selectivity for the A2A AR(19,Fig.6).81All these studies,performed by several laboratories,have strongly suggested reconsidering the xanthine family as A2A AR antagonists.In fact,such an antagonist,KW-6002(1,3-diethyl-8-(3-methoxystyryl)-7-methilxanthine,20,is already in phase II clinical trials for the treatment of basal ganglia disorders such as Parkinson’s disease.82Unfortunately,very recently,more detailed studies performed on MSX-2(19),in contrast with previous studies,clearly demonstrated that styryl xanthines at the solid state upon light irradiation led to dimmer derivatives which are almost inactive at the A2A AR.This should be considered a further limit of clinical use of styryl xanthine derivatives.83B.Polyheterocyclic DerivativesTheﬁrst promising A2A AR antagonist with a non-xanthine structure was CGS15943(21,9-chloro-2-(2-furanyl)[1,2,4]triazolo[1,5-c]quinazolin-5-amine),84,85which showed afﬁnity but not selectivity versus A1AR,A2B AR,and A3AR(Fig.7).86Nevertheless,it has represented the starting point for developing new non-xanthine structures as A2A AR adenosine antagonists.A few years later, bioisosteric replacement of the phenyl ring of CGS15943with an N7-substituted pyrazole led to the family of N8-substituted pyrazolo-triazolo-pyrimidines.Two selected compounds of this family named SCH58261(22,5-amino-7-(b-phenylethyl)-2-(2-furyl)pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine)and SCH63390(23,5-amino-7-(3-phenylpropyl)-2-(2-furyl)pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine)proved to be potent and selective A 2A AR antagonists both in rat and human models (Fig.7).87,88However,a major problem of this class of compounds is related to their low water solubility and consequently poor bioavailability.The introduction of a hydroxyl group at the para position on the phenyl ring of compounds 22and 23led to derivatives 24(5-amino-7-[b -(4-hydroxyphenyl)ethyl]-2-(2-furyl)pyrazolo[4,3-e ]1,2,4-triazolo[1,5-c ]pyrimidine)and 25(5-amino-7-[3-(4-hydroxyphenyl)-propyl]-2-(2-furyl)pyrazolo[4,3-e ]1,2,4-triazolo[1,5-c ]pyrimidine),which not only displayed greater hydrophilic character,but also a signiﬁcant increase of both afﬁnity and selectivity at the A 2A AR subtype,most probably due to hydrogen bond formation (Fig.7).Therefore,to understand the nature of the hydrogen bond,compound SCH 442416(26,5-amino-7-[3-(4-methoxyphenyl)-propyl]-2-(2-furyl)pyrazolo[4,3-e ]-1,2,4-triazolo[1,5-c ]pyrimidine)was synthesized.This derivative showed a surprising increase of afﬁnity for the A 2A adenosine receptor to qualify it as a candidate tool for PET studies in its 11C labeled form.The high afﬁnity was consistent with the compound acting as a hydrogen bond acceptor (Fig.7).89Figure 6.Structures and binding affinities of xanthines as A 2A AR antagonists.THERAPEUTIC ADENOSINE RECEPTOR ANT AGONISTS *141However,the introduction of oxygenated groups on the phenyl ring of the side chain was not sufﬁcient to confer the necessary water solubility,and the introduction of additional functionality resulted in a compelling need to address this problem.Toward this purpose,carboxylic and sulfonic moieties were introduced,which contributed greatly to the water solubility especially in the case of the sulfonic moiety,but a great loss of afﬁnity was observed.90A partial resolution to this problem was obtained by the former Zeneca group in proposing a compound named ZM241385(27,4-[2-[[7-amino-2-(2-furyl)[1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-yl]amino]ethyl]phenol),which proved to be one of the most potent A2A AR antagonists ever reported and having favorable water solubility(Fig.8).91However,ZM241385,which could be considered a simpliﬁed analog of the pyrazolo-triazolo-pyrimidine series,was found to bind also with good afﬁnity at the human A2B AR.In fact,its tritiated form is actually used in radioligand binding studies of this receptor subtype as well as at the A2A AR.92Recently,a large series of derivatives bearing various substituents at the5-position on the triazolo-triazine nucleus and the related triazolo-pyrimidine nucleus have been synthesized.In particular,derivative28showed great potency and selectivity for the A2A AR as compared with the A1AR(Fig.8).Nevertheless,the lack of binding data at the A2B and A3prevents a comparison of the derivatives with other fully characterized derivatives.Some of these derivatives,although not displaying exceptional high potency in binding studies,showed good oral efﬁcacy in a rodent catalepsy model of Parkinson’s disease.93–97Over the last few years,other classes of compounds have been investigated with the aim of obtaining new antagonist tools for studying A2A AR.Unfortunately,none of the reported compounds showed a better proﬁle than the above-mentioned derivatives.Only two classes of compounds,the triazolo-quinoxaline98and some pyrazolo-pyrimidines,99seem to possess promising requirements asA2A adenosine receptor antagonists(Fig.8).In the triazolo-quinoxaline series,only one compound29showed interesting A2A AR afﬁnity. Unfortunately,this nucleus seemed to be very sensitive to any kind of modiﬁcation.In fact,alkylation of the amino group,or its replacement with a carbonyl group,or substitution of the phenyl ring was detrimental in terms of afﬁnity at the A2A AR.In some cases,the afﬁnity at the human A3AR was predominant.Instead,in the pyrazolo-pyrimidine series,only one30showed a promising binding proﬁle,but was nevertheless of low potency and low selectivity for the A2A AR.C.Biological Actions of A2A Adenosine Receptor AntagonistsThe A2A AR antagonists that is furthest advanced in clinical trials is KW6002,as described above,and other antagonists of this subtype are under development.82,97,100The interest in CNS action of A2A AR antagonists also extends to impeding the neurodegenerative process4,7,8,10and possibly the treatment of stroke.101The peripheral actions of A2A AR antagonists might be complicated by a proinﬂammatory effect,102but might be therapeutically useful for cancer treatment.1034.A2B A D E N O S I N E R E C E P T O R A N T A G O N I S T SMost of the high afﬁnity receptor antagonists thus far reported have been xanthine derivatives. Consideration of the potential therapeutic applications of A2B AR antagonists,particularly their possible use an anti-asthmatic agents,104,105has stimulated many research groups to search for potentand selective antagonists for this subtype.Recognition of the possibility that the mechanism of action。

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