稻田生态系统汞的形态转化及同位素分馏

Transformation and Stable Isotope Fractionation of Mercury in the Rice Paddy Ecosystem

水稻是甲基汞的超富集农作物,汞污染区稻米普遍含有较高含量的甲基汞。食用大米是我国南方内陆居民人体甲基汞暴露的主要途径。水稻甲基汞污染问题已经引起了国际社会的高度关注。国内外学者围绕稻田生态系统汞的生物地球化学循环开展了大量的研究工作,取得了一系列重要研究成果。本文总结了稻田土壤汞的关键形态转化过程研究现状及存在问题,对未来需要进一步开展的研究工作进行了展望,包括:稻田土壤中汞的甲基化过程、影响因素及参与汞甲基化的主要微生物群落;典型汞矿区稻田土壤中汞的形态分布特征与参与甲基化反应的主要汞形态的识别;稻田土壤中汞的还原过程及对甲基化的影响;稻田生态系统汞的同位素分馏特征及汞的生物地球化学过程定量识别。

Rice had been highlighted in recent literatures as a bioaccumulator plant of methylmercury.Methylmercury contamination in rice is very common in Hg polluted areas.The rice consumption can be a main pathway of the methylmercury exposure to the inland population of Southern China,posing a potential threat to human.Scientific communities have paid a great attention to the issue of methylmercury accumulation in rice,and therefore,numerous researchers have focused on the biogeochemistry cycling of mercury in the rice paddy ecosystem.This review documents recent advances on the transformation of mercury species in the rice paddy and the existing research gaps.On the basis of gathered results,we further propose suggestions on the future research,including:identification of mercury methylators and the processes of Hg methylation in the rice paddy,speciation of mercury in the paddy soil in the mercury mining area and identification of the major mercury species that contribute mercury methylation in the paddy soil,identification of major mercury reduction processes in the paddy soil and their impact on mercury methylation,and mercury isotope fractionation in the rice paddy and tracing the geochemical processes in the paddy ecosystem.