杭州城区土壤的磁性与磁性矿物学及其环境意义_卢升高

第51卷第3期2008年5月

地　球　物　理　学　报

CH IN ES E JO U RN A L OF G EO PH YSICS

Vo l .51,N o .3M ay ,2008

卢升高,白世强.杭州城区土壤的磁性与磁性矿物学及其环境意义.地球物理学报,2008,51(3):762～769

Lu S G ,Bai S Q .M agnetic characterization and mag netic mine ralo gy o f the H ang zho u urba n soils and its envir onmental implications .Chinese J .Geophy s .(in Chinese ),2008,51(3):762～769

杭州城区土壤的磁性与磁性矿物学及其环境意义

卢升高,白世强

浙江大学环境与资源学院,杭州　310029

摘　要　对杭州城区四个不同功能区块土壤进行了系统的环境磁学测定,结果表明城市土壤的磁化率平均值为128×10-8m 3·kg -1,频率磁化率平均值3.6%(样品数=182),城市土壤呈现明显的磁性增强.城市土壤的磁化率与频率磁化率呈极显著指数负相关,表明城市土壤磁性增强明显区别于自然成土过程引起的以超顺磁性(SP )颗粒为主的表土磁性增强机理.统计分析表明,城市土壤磁化率与软剩磁和饱和等温剩磁(SI RM )呈显著直线正相关,说明亚铁磁性矿物是城市土壤剩余磁性的主要载体.综合等温剩磁获得曲线、热磁曲线、磁滞回线等岩石磁学测定和SEM /EDX 分析,城市土壤的磁性矿物以磁铁矿和赤铁矿为主,磁性矿物以假单畴-多畴(PSD -M D )颗粒存在,粒度明显大于成土过程形成的磁性颗粒,这些磁性颗粒主要来自燃料燃烧、汽车尾气等环境污染物.因此,城市土壤磁测可作为城市土壤污染监测、污染空间分布和污染物来源判断的新手段.关键词　城市土壤,环境磁学,磁性矿物,岩石磁学文章编号　0001-5733(2008)03-0762-08

中图分类号　P318

收稿日期2007-04-29,2008-01-28收修定稿

基金项目　国家自然科学基金(40771096)和浙江省自然科学基金杰出青年团队项目(R305078)资助.

作者简介　卢升高,男,1962年生,教授,博士生导师,主要从事环境磁学与环境生态学方面的研究.E -mail :lu sg @zju .edu .cn

Magnetic characterization and magnetic mineralogy of the Hangzhou urban soils

and its environmental implications

LU Sheng -Gao ,BAI Shi -Qiang

Colleg e o f Environmenta l and Res ou rce S ciences ,Zhejiang University ,Hang zho u 310029,China

A bstract A detailed mag netic study of urban soils in H angzhou City ,China ,w as carried out using

com bined

environmental

magnetism

and

ro ck

magnetism

techniques .Mag netic

measurements show ed that those urban soils have a sig nificant m ag netic enhancement ,w hich were characte rized by hig her magnetic susceptibility (average 128×10-8

m 3

·kg -1

)and mag netic rem anence ,and low frequency -dependent susceptibility (average 3.6%,N =182).Mag netic susceptibility v alues of urban soils show ed hig hly significant neg ative co rrelation w ith frequency -dependent susceptibility ,indicating that the mechanism of the m ag netic enhancem ent of urban soils is different fro m contribution of pedogenic ferrom ag ne tic mine rals in nature soils .Mag netic susceptibility values of urban soils ,on the other hand ,hav e significantly positive co rrelation with So ft IRM (IRM 20mT )and saturation isothe rm remanent mag netization (SIRM ),sugg esting that ferrimag netic mine rals are the main mag netic car riers .The co mbined rock magnetism (acquisition curves o f IRM ,temperature -dependent susceptibility and hysteresis measurem ent )and SEM /EDX (scanning electron micro sco py and energ y dispersive X -ray analy sis )revealed that mag netic mineralog y of urban soils is dominated by magnetite -like and hematite -like phases .The hy ste resis paramete rs sug gested that they a re pre sent mainly in the pseudo -single dom ain (PSD )and