蔬菜的硝态氮累积及菜地土壤的硝态氮残留_王朝辉

蔬菜的硝态氮累积及菜地土壤的硝态氮残留

王朝辉,宗志强,李生秀,陈宝明(西北农林科技大学资源环境学院,陕西杨陵

712100,E -mail:zhao -

huiw @)

摘要:在不同季节对11类、48种蔬菜的测定表明,硝态氮含量高于325mg #kg -1,达到4级污染水平的有20种,占调查总数的4117%,包括全部叶菜类、部分瓜类、根菜类和葱蒜类蔬菜.其中硝态氮含量高于700mg #kg -1,超过4级污染水平的有5种,均为叶菜类蔬菜.叶菜硝态氮累积虽为严重,但其中部分蔬菜叶片的硝态氮含量却低于3级污染水平.对不同类型菜地和农田土壤的测定发现,菜地0~200cm 各土层的硝态氮残留量均高于农田土壤,常年露天菜地200cm 土层的硝态氮残留总量为135818kg #hm -2,2年大棚菜田为141118kg #hm -2,5年大棚则达152019kg #hm -2,而一般农田仅为24514kg #hm -2.菜地土壤的硝态氮残留严重威胁菜区地下水环境.关键词:蔬菜;土壤;硝态氮累积;硝态氮残留

中图分类号:S15813 文献标识码:A 文章编号:0250-3301(2002)03-05-0079

基金项目:国家重点基础研究专项经费资助项目

(G1999011707);国家自然科学基金项目(49890330,39970429,30070429)

作者简介:王朝辉(1968~),男,河北元氏人,博士,副教授,从

事旱地土壤和作物系统氮素动态及其生态环境效应方面的研究.

收稿日期:2001-04-13;修订日期:2001-07-27

Nitrate Accumulation in Vegetables and Its Residual in Vegetable Fields

Wang Zhaohui,Zong Zhiqiang,Li Shengx iu,Chen Baom ing (Colleg e of Resources and Env ironmental Sc-i ences ,Nort hw estern Science and T echnology U niversity of A griculture and Forestry ,Yang ling,Shaanx i 712100,China,E -mail:zhaohuiw @public.x )

Abstract:Deter minations o f 11kinds,48varieties o f vegetables w ere car ried out at different seaso ns.T he results show ed

t hat nitr ate -N concentrations in 20veg etables reached Pollution L evel 4(N O -3-N>325mg #kg

-1

),w hich accounted for 4117%of the total number of the sampled veg etables and included all of the leafy ,and most of the melon,root,onion

and garlic v eg etables.Among them,5leafy vegetables even ex ceeded L evel 4(N O -3-N >700mg #kg

-1

).A lthough leafy vegetables w er e usually apt to heavily accumulate nitrate,most of them w er e w ith nitrate -N concentrations lower

t han Level 3(NO -3-N <325mg #kg -1

)in leav e blades.Fur ther investig ation show ed that vegetable soils accumulated mor e nitrates in each lay er fro m 0cm to 200cm t han did cer eal crop soil.T he total amount of residual nitrate -N was

135818kg #hm -2in the 200cm soil profile of usual v egetable fields,and 141118kg #hm -2and 152019kg #hm -2

in the 2-yaers and the 5-years long plastic greenhouse fields r espectiv ely,how ever that in t he cereal crop fields was only 24514kg

#hm -2

.N itrate residual in vegetable soils for med ser ious threats to underground water in vegetable grow ing ar eas.Keywords:v eg etable;soil;nitrate accumulation;nitrate residual

人类摄入的硝态氮有72%~94%来自蔬菜

[1]

,蔬菜硝态氮累积对人类健康的危害已引

起世界各国的重视[2,3]:荷兰规定莴笋的硝态氮含量不能超过1017mg #kg -1;德国规定菠菜不能超过791mg #kg -1[4]

.1997年欧共体对叶类

蔬菜规定了更为严格的标准[5]

.1982年沈明珠

等对我国34种蔬菜进行了检测,发现10种蔬菜硝态氮含量超过325mg #kg -1,达4级污染水平[6].近年来,为了提高蔬菜产量,满足市场不断增长的需求,菜农大量施用化学肥料,特别是氮肥,一些地方施氮量高达3300kg #hm -2[7]

,

超过作物需求量的数倍.

伴随着过量施用氮肥,环境污染也日益严重:未被作物吸收而残留在土壤中的氮素是水体和大气氮污染的重要来源.据估计,每年随径流或降水流入河、湖中的氮素约有60%来自施入农田的化肥[8].京、津、唐地区69个观测点的地下水,半数以上硝态氮含量超标,高者达6717m g #kg

-1[9]

;黄土高原中南部的渭北旱塬

第23卷第3期2002年5月

环 境 科 学ENVIRONM ENTAL SCIENCE

V ol.23,N o.3M ay,2002