The divergent effects of nitrate and ammonium application on mercury methylation, demethylation, and reduction in flooded paddy slurries

Using Mercury Stable Isotopes to Quantify Directional Soil–Atmosphere Hg(0) Exchanges in Rice Paddy Ecosystems: Implications for Hg(0) Emissions to the Atmosphere from Land Surfaces

“…Although large-scale Hg mining activities in the Wanshan Hg mining area ceased in 2003, Hg concentrations in the air (37.3–416 ng m –3 ) were consistently higher than the background value in Guizhou (2.8–8.2 ng m –3 ). Previous studies reported that, in addition to significant methylation processes, the Hg­(II) reduction process was also active in paddy soils in this study area, − which may be the main cause for the consistently high atmospheric Hg(0) concentrations. Therefore, this artisanal Hg mining site was selected for examining soil–atmosphere Hg(0) flux exchanges.…”

“…Rice paddies are the largest human-made wetlands and account for approximately 18% of the global total wetlands . Hg­(II) reduction through photoreduction, microbial reduction, and abiotic dark reduction processes can lower the concentration of substrates available for Hg-methylation, and is thus a critical step of Hg cycling in paddy soils. − However, the relative importance of the above-mentioned reduction processes for Hg(0) emissions from paddy soils remains elusive, mainly due to traditional observations of Hg(0) concentration and exchange flux not being able to distinguish Hg(0) emitted from different reduction processes.…”