土壤-植物系统“硒-汞拮抗”研究进展综述

Reviews on selenium-mercury antagonism in soil-plant systems

汞(Hg)是一种高毒性、全球性的持久性污染物,其各种形态中甲基汞的毒性较高.随着工业化进程的发展,土壤汞污染问题愈发严重,尤其是在中国内陆汞污染地区,稻米中甲基汞浓度超标问题亟待解决.水生系统中大量研究表明,"硒-汞拮抗"可显著降低汞的风险.然而对于陆生系统中硒-汞作用机理,尤其是土壤-植物体系中"硒-汞拮抗"的研究还处于起步阶段.近期研究发现,硒(Se)可以通过形成Hg-Se复合物将汞钝化或固定在土壤中或植物根部,且有效降低土壤中甲基汞的净生成量(如通过微生物作用生成)及其在植物中富集.土壤中"硒-汞作用"过程可能是控制土壤-水稻体系中"硒-汞拮抗"的关键过程,土壤氧化-还原条件变化过程中硒、汞和硫的生物地球化学行为(如微生物介导的形态变化),对土壤-植物体系中"硒-汞拮抗"的调节至关重要.归纳了土壤-植物体系中"硒-汞拮抗"的最新研究进展,总结其可能的内在机制,并对其未来的研究方向提出建议.

Mercury（Hg）is a highly toxic,persistent and global pollutant,methylmercury（MeHg）is one of the most toxic species of Hg.There are growing concerns about Hg pollution in soils,along the process of industrialization.Especially,in some inland areas in China,high levels of MeHg in rice grains became an on-going problem.A number of studies in aquatic systems indicate that antagonistic interactions between mercury and selenium（Se）could evidently reduce risk of Hg.However,little is known about Hg-Se interactions in terrestrial systems,especially in soil-plant systems.Recent studies reveal that complexation between Se and Hg could reduce mobility and bioavailability of Hgin soils and in the rhizosphere,resulting in reduced net production of MeHg in soils（e.g.via microbial methylation processes）and its accumulation in plants.Particularly in soil-rice systems,interactions between Hg and Se in soils could be the key process controlling Hg-Se antagonism.Besides,the biogeochemical processes of selenium,mercury and sulfur（e.g.,microbe-mediated changes in speciation）under fluctuating redox potentials,could also be important in controlling Hg-Se antagonism in soil-rice systems.In this review,we mainly aimed at summarizing recent progresses in understanding Hg-Se antagonism in soil-plant systems,as well as the underlying mechanisms,which may provide avenues for future research.