title: Mechanistic understanding of MeHg-Se antagonism in soil-rice systems: the key role of antagonism in soil.
abstract: Methylmercury (MeHg) accumulation in rice has great implications for human health. Here, effects of selenium (Se) on MeHg availability to rice are explored by growing rice under soil or foliar fertilization with Se. Results indicate that soil amendment with Se could reduce MeHg levels in soil and grain (maximally 73%). In contrast, foliar fertilization with Se enhanced plant Se levels (3-12 folds) without affecting grain MeHg concentrations. This evidence, along with the distinct distribution of MeHg and Se within the plant, demonstrate for the first time that Se-induced reduction in soil MeHg levels (i.e., MeHg-Se antagonism in soil) rather than MeHg-Se interactions within the plant might be the key process triggering the decreased grain MeHg levels under Se amendment. The reduction in soil MeHg concentrations could be mainly attributed to the formation of Hg-Se complexes (detected by TEM-EDX and XANES) and thus reduced microbial MeHg production. Moreover, selenite and selenate were equally effective in reducing soil MeHg concentrations, possibly because of rapid changes in Se speciation. The dominant role of Se-induced reduction in soil MeHg levels, which has been largely underestimated previously, together with the possible mechanisms advance our mechanistic understanding about MeHg dynamics in soil-rice systems.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, P.R. China.
authors.forename: Fei
authors.initials: F
authors.lastname: Dang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China.|Environmental and Resource Studies Program (ERS), Trent University, Peterborough, Ontario, Canada.
authors.forename: R Douglas
authors.initials: RD
authors.lastname: Evans
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China.|Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhong
authors.affiliation: Key Lab for Biomedical Effects of Nanomaterial and Nanosafety, Laboratory of Metallomics and Metalloproteomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P.R. China.
authors.forename: Jiating
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, P.R. China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Zhou
mesh_terms: D004784:Environmental Monitoring; D008628:Mercury; D012275:Oryza / Q000737:chemistry*; D012643:Selenium; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants
chemical_list: D012987:Soil; D012989:Soil Pollutants; D008628:Mercury; D012643:Selenium