title: Effects of incorporating differently-treated rice straw on phytoavailability of methylmercury in soil.
abstract: Differently-treated crops straw is being widely used to fertilize soil, while the potential impacts of straw amendment on the biogeochemistry and phytoavailability of mercury in contaminated soils are largely unknown. In the present study, differently-treated rice straw (dry straw, composted straw, straw biochar, and straw ash) was incorporated into mercury-contaminated soil at an environment relevant level (1/100, w/w), and mercury speciation, methylmercury (MeHg) phytoavailability (using ammonium thiosulfate extraction method, validated elsewhere) and bioaccumulation (in Indian mustard Brassica junceas) were quantified. Our results indicated that incorporating straw biochar or composted straw into soil would decrease phytoavailable MeHg levels, possibly due to the strong binding of MeHg with particulate organic matter in amended straw ('MeHg immobilization effect'). Consequently, MeHg accumulation in aboveground tissue of Indian mustard harvested from straw biochar-amended soil decreased by 20% compared to the control. Differently, incorporation of dry straw resulted in elevated MeHg levels in soil ('Mercury methylation effect'). Decomposition of amended dry straw in soil would evidently increase DOC levels (averagely 40%-195% higher than the control), which may subsequently mobilize MeHg in the soil ('MeHg mobilization effect'). Accordingly, incorporation of dry straw led to increased phytoavailable MeHg levels in the soil and doubled MeHg accumulation in Indian mustard. Our results provided the first evidence that incorporating differently-treated rice straw into soil could have diverse effects on mercury biogeochemistry and phytoavailability, which should be taken into account in risk assessment or soil remediation.
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, People's Republic of China. Electronic address: 244654741@qq.com.
authors.forename: Rui
authors.initials: R
authors.lastname: Shu
authors.affiliation: State Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu Province, People's Republic of China. Electronic address: fdang@issas.ac.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Dang
authors.affiliation: School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, People's Republic of China. Electronic address: zhonghuan@nju.edu.cn.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhong
mesh_terms: D000383:Agriculture; D002606:Charcoal / Q000737:chemistry; D004784:Environmental Monitoring; D008767:Methylmercury Compounds / Q000378:metabolism*; D009149:Mustard Plant / Q000378:metabolism*; D012275:Oryza / Q000737:chemistry / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism*; D013885:Thiosulfates / Q000737:chemistry*
chemical_list: D008767:Methylmercury Compounds; D012989:Soil Pollutants; D013885:Thiosulfates; C540010:biochar; D002606:Charcoal; C035309:ammonium thiosulfate
keywords: Ammonium thiosulfate; Bioavailability; Chemical extraction; Methylmercury; Straw return