甲醇化工厂周边土壤重金属形态与浸出特征研究

Speciation and Leaching Characteristics of Heavy Metals in Soil Around a Methanol Chemical Factory

【目的】以湖南省益阳市桃江县某甲醇化工厂周边不同类型土壤为研究对象,分析重金属形态分布及浸出特征,以期为该类化工厂周边土壤的风险管控提供理论依据。【方法】采用改进BCR法、TCLP法分别研究土壤重金属形态分布和毒性浸出特征,并对重金属形态与浸出含量进行相关分析。【结果】土壤中主要重金属污染物为铅(Pb)、镉(Cd)和铬(Cr),其中水田Cd含量为农用地土壤污染风险管制值的43倍。BCR提取结果显示:残渣态是土壤重金属最主要形态,占总量的33%~43%,可氧化态含量最低,仅占总量的10%~13%;林地弱酸可提取态比例系数低于水田。TCLP浸提结果显示,Cr、Pb、Cd的浸出率分别为9.09%~11.36%、7.68%~12.10%和14.68%~22.64%,浸出含量均为水田>林地,且均超标。弱酸可提取态与TCLP浸出含量呈极显著正相关(r=0.999,P<0.01)。【结论】该化工厂周边土壤Cr、Pb和Cd均超标,存在严重的环境风险,且水田的环境风险较林地更大,需要严格管控。此外,可以根据弱酸可提取态含量评价该化工厂周边土壤重金属的生物有效性和潜在风险。

【Objective】The speciation distribution and leaching characteristics of heavy metals in soil around a methanol chemical factory in Taojiang County,Yiyang City,Hunan Province were studied,in order to provide a theoretical basis for risk management.【Method】Modified BCR and TCLP method were used to determine the speciation distribution characteristics and toxic leaching characteristics of heavy metals.The correlation between the speciation and toxic leaching content of heavy metals was analyzed.【Result】It showed that the major heavy metal pollution elements were Pb,Cd and Cr.In particular,Cd was 43 times of the risk control value.BCR sequential extraction showed that the residual fraction was the highest,accounting for 33%~43%of the total metal content,and the oxidizable fraction was the lowest,accounting for only 10%~13%of the total.The weak acid extractable fraction was lower for the forest soil than for the farmland soil.The TCLP leaching rates of Cr,Pb and Cd were 9.09%~11.36%,7.68%~12.10%and 14.68%~22.64%,respectively.The leaching content of Cr,Pb and Cd in the farmland was higher than that in the forest,and they all exceeded the standard.The weak acid extractable fraction and the TCLP leaching content were significantly positive correlated(r=0.999,P<0.01).【Conclusion】The soil around the chemical plant has serious environmental risk,and the farmland soil is much worse than the forest soil,therefore needs strict control.Moreover,the weak acid extractable fraction can be used to evaluate the bioavailability and environmental risks.