title: Effects of rice residue incorporation on the speciation, potential bioavailability and risk of mercury in a contaminated paddy soil.
abstract: To reduce air pollution, straw return instead of burning is being strongly encouraged in China, including some mercury polluted areas. Nevertheless, the possible influences of straw return on methylation, bioavailability and exposure risk of mercury were relatively unknown. In this study, different amounts of rice straw or root were added into a mercury contaminated soil. Potential bioavailability of soil-bound mercury to crops/deposit-feeders was assessed by quantifying extraction rates of mercury (%) by calcium chloride (CaCl2)/bovine serum albumin (BSA). Extraction rates of inorganic mercury (IHg) or methylmercury (MMHg) decreased significantly in rice residue amended soils, possibly due to the strong binding of mercury with organic matter in root/straw. Meanwhile, MMHg concentrations increased by 2-8 times in amended soils. Such increases were attributed to enhanced microbial activities and/or formation of Hg-S-DOM complexes after rice residue incorporation and decomposition. Consequently, potential exposure risk of IHg (quantified as concentration of potentially bioavailable mercury in soil) decreased significantly while that of MMHg increased up to 4 times. To our knowledge, this is the first study demonstrating that rice residue incorporation could significantly affect biogeochemistry of both IHg and MMHg in soils, which should be considered in straw incorporation activities in mercury polluted areas.
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China.
authors.forename: Huike
authors.initials: H
authors.lastname: Zhu
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China. Electronic address: zhonghuan@nju.edu.cn.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhong
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China; Environmental and Resource Studies Program, Trent University, Peterborough, Ontario, Canada.
authors.forename: Douglas
authors.initials: D
authors.lastname: Evans
authors.affiliation: Department of Chemistry, Trent University, Peterborough, Ontario, Canada.
authors.forename: Holger
authors.initials: H
authors.lastname: Hintelmann
mesh_terms: D000383:Agriculture / Q000379:methods; D001682:Biological Availability; D002122:Calcium Chloride / Q000737:chemistry; D004787:Environmental Pollution / Q000517:prevention & control; D008628:Mercury / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000737:chemistry*; D012275:Oryza; D012306:Risk; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D018505:Waste Management / Q000379:methods; D014866:Waste Products
chemical_list: D008767:Methylmercury Compounds; D012989:Soil Pollutants; D014866:Waste Products; D012710:Serum Albumin, Bovine; D008628:Mercury; D002122:Calcium Chloride
keywords: Chemical extraction; Methylmercury; Rice straw return; Sequential extraction; Soil organic matter