作　　者： (谷成）; (钟寰）; (张慧玲）; (刘玉荣）;

机构地区： 南京大学环境学院,污染控制与资源化研究国家重点实验室,南京210093

出　　处： 《科学通报》 2017年第24期2717-2723,共7页

摘　　要： 秸秆还田是一项正大力推广的农业措施,既可避免秸秆焚烧导致的空气污染,又可通过提升土壤肥力、改善土壤性质而促进作物生长.与此同时,秸秆还田对农田重金属生态风险的影响值得关注.已有不少研究报道了秸秆还田导致铜、镉、锌等重金属生物有效性下降,然而秸秆还田对土壤中汞环境行为与风险的影响却鲜有报道.本文综述了近年来秸秆还田影响汞污染地区"稻田汞"行为与风险的研究进展.近期研究揭示秸秆还田可显著提升"稻田汞"的生态风险:秸秆还田可影响"稻田汞"的地球化学相态分布、汞的微生物甲基化、汞的生物有效性,以及汞的植物累积,并讨论了这些影响可能的内在机制(如微生物活性上升、秸秆产生溶解性有机质导致汞活性上升等).本文所阐述的信息,有助于从机理层面理解陆生系统中汞的行为与风险,并有助于汞污染地区有关秸秆处理方式的决策. It is well-known that interactions between Hg and organic matter could greatly affect biogeochemistry of Hg in soils, and its subsequent uptake by plants. Crop straw is mainly composed of organic matter, and its incorporation into soils may have impacts on Hg dynamics in soil-plant systems. Straw return is being widely encouraged, in order to mitigate straw-burning induced air pollution, as well as to promote plant growth by increasing soil fertility and improving the soil. Meanwhile, potential impacts of straw return on the ecological risk of metals in agricultural soils warrant investigation. While much progresses have been made in understanding the reduced metal bioavailability （e.g., for Cu, Cd and Zn） under straw amendment, little is known about the potential effects of straw return on Hg dynamics in soils and the associated ecological risks. Here, we summarize recent advances in understanding Hg dynamics in soil-rice systems under straw amendment. Recent studies revealed evidently enhanced ecological risk of Hg in paddy soils under straw amendment. Especially, straw return was found to have positive effects on methylmercury （MeHg） concentrations in soils, as well as those in crops. The underlying mechanisms may include： （1） Straw amendment has evident effects on the geochemical fractionation of Hg in soils, by facilitating transformation of Hg from the refractory fractions （e.g., residual fractions, including HgS） to more mobile fractions （e.g., organic-complexed fraction）, which may increase availability of inorganic Hg to microbial methylators. （2） Transformation of inorganic Hg to MeHg was facilitated under straw amendment, which could be mainly attributed to the increased availability of inorganic Hg as well as enhanced activities of microbial methylators （e.g., sulfate reducing bacteria）. （3） Straw return was found to have positive effects on Hg accumulation in grains of crops. The observed effects could be explained by the increased soil MeHg levels, enhanced mobility

关 键 词： 秸秆还田 土壤 汞 水稻 有机质