天津污灌区盐分累积对土壤汞赋存形态的影响  

A simulation study on the effect of salinity on the fractions distribution of exogenous mercury in the wastewater-irrigated area of Tianjin City

作　　者：郑顺安 韩允垒[3] 李晓华[1] 薛颖昊 段青红 郑向群 

机构地区：[1]农业部农业生态与资源保护总站,北京100125 [2]农业部环境保护科研监测所,天津300191 [3]中国农学会,北京100125

出　　处：《中国环境科学》2017年第5期1858-1865,共8页China Environmental Science

基　　金：国家自然科学基金资助项目(41203084;41371463);国家水体污染控制与治理科技重大专项(2015zx07103-007);国家重点研发计划(2016YFD0201306)

摘　　要：应用稳定同位素^(202)Hg稀释技术,通过培养试验及改进的Tessier连续提取法,分析同位素比值R_(Hg)(^(202)Hg/^(200)Hg)的变化情况及同位素可交换态含量(E值),探索盐渍化对外源汞在天津潮土中形态分布及有效性的影响.主要盐分NaCl和Na_2SO_4,设置的盐度梯度为7个,添加质量分数为0%~5%.结果表明,外源^(202)Hg进入NaCl处理的土壤后,同位素比值R_(Hg)变化最为显著的形态集中在交换态(含水溶态)、胡敏酸结合态和富里酸结合态,对碳酸盐结合态、铁锰氧化物结合态、有机质结合态、残渣态的影响较小,其中交换态、富里酸结合态的同位素比值R_(Hg)大幅度上升,富里酸结合态含量显著下降.Na_2SO_4处理的土壤各形态Hg的同位素比值与对照土壤相比均不显著,基本保持稳定.5%NaCl处理下土壤Hg的E值相比对照提高了51%,土壤Hg同位素可交换态含量E值与Cl^-含量呈现显著的正相关关系,取对数后的一元回归方程为lny=0.0961lnx+4.895(x为Cl^(-1)含量,y为E值,n=7,R^2=0.918).研究表明,高浓度的NaCl环境对外源Hg在土壤中形态分布有显著影响,土壤的盐渍化趋势会使汞释放及作物吸收风险更趋严重.This study was designed to pinpoint the effect of salinity(NaCl and Na2SO4,add at salinity levels of0~5%,respectively)on the species distribution of exogenous Hg(II)in wastewater-irrigated areas of Tianjin City.The fractions distribution of mercury in the studied fluvo-aquic soils were investigated by a modified Tessier scheme of sequential extraction procedures(SEPs),which detected with a quantitative analytical method and an isotopic202Hg labeling method,respectively.Furthermore,the pools of isotopically exchangeable Hg(E-value)in soils which used as indictor of content of soil available Hg were also calculated based on the isotope ratios of RHg(202Hg/200Hg).It was showed that after amendments of exogenous202Hg in salt-amended soils,isotope ratios of RHg(202Hg/200Hg)significantly varied in exchangeable(including water-soluble),fulvic acid and humic acid fractions,while barely changed in the fractions of carbonate,Fe/Mn oxides,organic,and residual species.It was also found that by comparison of the control without salt amendment,NaCl spiked to soils resulted in the more movement of exogenous202Hg toward more instable fractions,including water exchangeable and fulvic acid fractions,while the distribution of exogenous Hg speciation in soils was not significantly influenced by Na2SO4.The content of isotopic exchangeable fraction(E-value)in5%NaCl-amended soil increased by51%compared with that in the control soil.E-value as a function of Cl-1content in soil could be simulated by linear model(lnE=0.0961lnCl+4.895,n=7,R2=0.918).The study manifested that NaCl can significantly increase migration of Hg(II)in the soil irrigated with wastewater,which may enhance Hg(II)bioavailability in the soil and cause a hazard to surface water.Especially,it will be harmful to human body through the food chain.

关 键 词：污灌区 汞 土壤 赋存形态 盐分 

分 类 号：X53[环境科学与工程—环境工程]