title: Biochar amendment reduced methylmercury accumulation in rice plants.
abstract: There is growing concern about methylmercury (MeHg) accumulation in rice grains and thus enhanced dietary exposure to MeHg in Asian countries. Here, we explored the possibility of reducing grain MeHg levels by biochar amendment, and the underlying mechanisms. Pot (i.e., rice cultivation in biochar amended soils) and batch experiments (i.e., incubation of amended soils under laboratory conditions) were carried out, to investigate MeHg dynamics (i.e., MeHg production, partitioning and phytoavailability in paddy soils, and MeHg uptake by rice) under biochar amendment (1-4% of soil mass). We demonstrate for the first time that biochar amendment could evidently reduce grain MeHg levels (49-92%). The declines could be attributed to the combined effects of: (1) increased soil MeHg concentrations, probably explained by the release of sulfate from biochar and thus enhanced microbial production of MeHg (e.g., by sulfate-reducing bacteria), (2) MeHg immobilization in soils, facilitated by the large surface areas and high organosulfur content of biochar, and (3) biodilution of MeHg in rice grains, due to the increased grain biomass under biochar amendment (35-79%). These observations together with mechanistic explanations improve understanding of MeHg dynamics in soil-rice systems, and support the possibility of reducing MeHg phytoaccumulation under biochar amendment.
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, People's Republic of China, People's Republic of China.
authors.forename: Rui
authors.initials: R
authors.lastname: Shu
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, People's Republic of China, People's Republic of China.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, People's Republic of China, People's Republic of China; Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada. Electronic address: zhonghuan@nju.edu.cn.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhong
mesh_terms: D002606:Charcoal / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000378:metabolism*; D012275:Oryza / Q000378:metabolism*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; D012989:Soil Pollutants; C540010:biochar; D002606:Charcoal
keywords: Bioaccumulation; Biochar; Methylmercury; Rice paddy soil