Mobilization, Methylation, and Demethylation of Mercury in a Paddy Soil under Systematic Redox Changes
Journal
Environmental Science and Technology
Journal Volume
55
Journal Volume
55
Journal Issue
14
Journal Issue
14
Pages
10133-10141
Start Page
10133
End Page
10141
ISSN
0013936X
Date Issued
2021-07-20
Author(s)
Wang, Jianxu
Shaheen, Sabry M.
Jing, Min
Anderson, Christopher W. N.
Swertz, Ann-Christin
Feng, Xinbin
Rinklebe, Jörg
Abstract
Methylmercury (MeHg) contamination in paddy fields is a significant environmental issue globally since over half of the population of our planet consumes rice. MeHg is a neurotoxin produced by microorganisms in oxygen-limited environments. Microbial effect on MeHg production is a hotspot of research; however, it has been largely ignored how the oxidation-reduction potential (Eh) shapes MeHg formation. Here, we elucidated Hg (de)-methylation in a contaminated soil by increasing Eh stepwise from -300 to +300 mV using a sophisticated biogeochemical microcosm. At the Eh range from -300 to -100 mV, high MeHg concentration and dissolved total Hg (THg) concentration were found due to a high relative abundance of Hg-methylation bacteria (e.g., Desulfitobacterium spp.), acidification, and reductive dissolution of Fe(oxyhydr)oxides. At the Eh range from 0 to +200 mV, the formation of colloids leads to adsorption of Hg and as a result colloidal Hg increased. MeHg reduction with Eh (-300 to +200 mV) increase was mainly attributed to a reduced Hg methylation, as dissolved THg and relative abundance of Desulfitobacterium spp. decreased by 50 and 96%, respectively, at Eh of +200 mV as compared to Eh of -300 mV. Mercury demethylation might be less important since the relative abundance of demethylation bacteria (Clostridium spp.) also decreased over 93% at Eh of +200 mV. These new results are crucial for predicting Hg risks in paddy fields.
Subjects
biogeochemical cycle
Hg (de-)methylation process
mercury redox chemistry
risk management
Publisher
American Chemical Society
Type
journal article