有机硫影响稻田土壤甲基汞的产生

Effect of organic sulfur on the production of methylmercury in paddy soil

为了探讨有机硫化合物在无机汞甲基化过程中所起的作用,以泉州市某企业周边的汞污染稻田土壤为试验材料,以还原型谷胱甘肽为有机硫,采用室内土壤模拟试验的方法,研究了3个浓度(0、500、1000 mg·kg^(-1))的有机硫施加对土壤中汞甲基化及甲基汞生物有效性的影响。结果表明:和对照组相比,谷胱甘肽添加显著提高了土壤中铁、锰的溶出以及土壤中可溶性碳的含量。此外,谷胱甘肽施用也显著提高了土壤中甲基汞的产生和甲基汞的溶出,对土壤固相中甲基汞的增加率为87.36%~212.48%,对土壤溶液中甲基汞的增加率为4380.00%~5890.30%。相关性分析和逐步回归模型表明,土壤中可溶性铁的含量是影响汞甲基化和甲基汞生物有效性的关键因子。研究表明,有机硫促进了汞甲基化,有机硫化合物影响汞甲基化过程不只是有机硫和汞的络合作用,土壤中铁、锰氧化物所起的作用也不容忽视。

In order to examine the role of organic sulfur compounds in the process of inorganic mercury(Hg)methylation,Hgcontaminated paddy soils were collected from the vicinity of a gold mine in Quanzhou,Fujian Province.The effects of three gradients of organic sulfur(0,500 mg·kg^(-1),and 1000 mg·kg^(-1) reduced glutathione)on the methylation of inorganic Hg in the soil and the bioavailability of methylmercury(MeHg)were investigated based on microcosm experiments.The results showed that compared with the control group,the addition of glutathione significantly increased the dissolution of iron and manganese in soil,and also increased the contents of dissolved carbon.In addition,glutathione application markedly enhanced the production and the dissolution of MeHg in soil.The rates of MeHg increase in the soil solid phase and soil solution were 87.36%~212.48%and 4380.00%~5890.30%,respectively.Correlation and stepwise regression model analyses revealed that the content of soluble iron in soil was a key factor affecting the methylation of inorganic Hg and the bioavailability of MeHg.The findings of this study indicate that the roles of iron and manganese oxides in the soil should be taken into consideration when assessing the effects of organic sulfur compounds on the methylation of Hg in soil.