TY - JOUR
T1 - Biochar-impacted sulfur cycling affects methylmercury phytoavailability in soils under different redox conditions
AU - Wang, Yongjie
AU - Zhang, Yue
AU - Ok, Yong Sik
AU - Jiang, Tao
AU - Liu, Peng
AU - Shu, Rui
AU - Wang, Dingyong
AU - Cao, Xinde
AU - Zhong, Huan
N1 - Funding Information:
This work was supported by the National Natural Science Foundation of China (grant numbers 41673075 ; 41771508 ). Sulfur K-edge XANES measurements were carried out at beamline 4B7A at Beijing Synchrotron Radiation Facility (BSRF). We thank the staff of 4B7A for their assistance during the experiments and in the data analysis.
PY - 2020
Y1 - 2020
N2 - Recently, there has been increasing interest in reducing methylmercury (MeHg) phytoavailability using biochar, although the underlying mechanisms are not fully understood. By combining lab-scale batch incubation with pot and field validations, we demonstrate that biochar-impacted sulfur cycling in soils and MeHg-soil binding play key roles in controlling MeHg phytoavailability. (1) Under anoxic conditions, biochar-associated sulfate and biochar-facilitated microbial sulfate reduction enhanced the production of reduced inorganic sulfur species as acid-volatile sulfide (AVS) in soils by 122%, facilitating MeHg binding with soils and thus reducing MeHg phytoavailability. (2) In contrast, under oxic conditions, the reduced inorganic sulfur was oxidized (resulting in a 68–91% decrease in AVS), which released soil-bound MeHg and increased MeHg phytoavailability. The proposed mechanisms could explain the distinct effects of biochar amendment on MeHg bioaccumulation observed under anoxic (10–88% lower in rice grains) and oxic conditions (48–84% higher in wheat grains). Our results dispute the commonly held assumption that reduced MeHg phytoavailability under biochar amendment can be primarily attributed to MeHg-biochar binding. Therefore, the potential increased risk of MeHg in oxic soils following biochar amendment should be evaluated in more detail.
AB - Recently, there has been increasing interest in reducing methylmercury (MeHg) phytoavailability using biochar, although the underlying mechanisms are not fully understood. By combining lab-scale batch incubation with pot and field validations, we demonstrate that biochar-impacted sulfur cycling in soils and MeHg-soil binding play key roles in controlling MeHg phytoavailability. (1) Under anoxic conditions, biochar-associated sulfate and biochar-facilitated microbial sulfate reduction enhanced the production of reduced inorganic sulfur species as acid-volatile sulfide (AVS) in soils by 122%, facilitating MeHg binding with soils and thus reducing MeHg phytoavailability. (2) In contrast, under oxic conditions, the reduced inorganic sulfur was oxidized (resulting in a 68–91% decrease in AVS), which released soil-bound MeHg and increased MeHg phytoavailability. The proposed mechanisms could explain the distinct effects of biochar amendment on MeHg bioaccumulation observed under anoxic (10–88% lower in rice grains) and oxic conditions (48–84% higher in wheat grains). Our results dispute the commonly held assumption that reduced MeHg phytoavailability under biochar amendment can be primarily attributed to MeHg-biochar binding. Therefore, the potential increased risk of MeHg in oxic soils following biochar amendment should be evaluated in more detail.
KW - Bioavailability
KW - Mercury
KW - Rice
KW - Soil remediation
KW - Wheat
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U2 - 10.1016/j.jhazmat.2020.124397
DO - 10.1016/j.jhazmat.2020.124397
M3 - Article
AN - SCOPUS:85095829589
VL - 407
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
SN - 0304-3894
M1 - 124397
ER -