Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Abstract

We examined the composition and spatial correlation of sulfur and mercury pools in peatland soil profiles by measuring sulfur speciation by 1s X-ray absorption near-edge structure spectrocopy and mercury concentrations by cold vapor atomic fluorescence spectroscopy. Also investigated were the methylation/demethylation rate constants and the presence of hgcAB genes with depth. Methylmercury (MeHg) concentration and organic disulfide were spatially correlated and had a significant positive correlation (p < 0.05). This finding is consistent with these species being products of dissimilatory sulfate reduction. Conversely, a significant negative correlation between organic monosulfides and MeHg was observed, which is consistent with a reduction in Hg­(II) bioavailability via complexation reactions. Finally, a significant positive correlation between ester sulfate and instantaneous methylation rate constants was observed, which is consistent with ester sulfate being a substrate for mercury methylation via dissimilatory sulfate reduction. Our findings point to the importance of organic sulfur species in mercury methylation processes, as substrates and products, as well as potential inhibitors of Hg­(II) bioavailability. For a peatland system with sub-μmol L–1 porewater concentrations of sulfate and hydrogen sulfide, our findings indicate that the solid-phase sulfur pools, which have a much larger sulfur concentration range, may be accessible to microbial activity or exchanging with the porewater.

Study on the variation of MeHg content in different types of soils in non-ferrous metallurgical areas

“…It has been proved (Gerbig, Kim, Stegemeier, Ryan, & Aiken, 2011; Qiu, Guangle, Feng, Xinbin, Wang, Shaofeng, & Shang, Lihai, 2006), that soluble sul de in soil has a great in uence on MeHg concentration in soil, and sul de can inhibit MeHg formation in soil because soluble sul de can combine with Hg(II) in the soil to form insoluble mercury sul de, which makes it di cult for the methylation microorganism of mercury to use, thus reducing MeHg formation. In this experiment, there was no signi cant correlation between MeHg content and sul de in paddy soils under ooded conditions (p > 0.05), while the remaining four soils showed a negative correlation between MeHg content and soluble sul de, among which, dryland soils and cultivated wasteland soils showed a signi cant negative correlation, this is consistent with the ndings of Caroline E. Pierce on the effect of sul de on mercury methylation in peatland soils (Pierce et al, 2022). The increase in sul de may be due to the respiration of SRB, which converts soil sulfate to sul de (Benoit, Gilmour, & Mason, 2001), which reduced the available state of Hg in the soil and inhibited the production of MeHg in the soil.…”

Mercury methylation and methylmercury demethylation in boreal lake sediment with legacy sulphate pollution

“…, Pierce et al , 2022 (ref. 69)) was not available as part of this study, the bulk of evidence suggests that a build-up of sulphur and internal cycling in the sediment (due to historical sulphate loading) is the causative factor for the elevated MeHg concentration and production in the sulphate-impacted lake. This is supported by the otherwise immediate proximity of the two lakes, their similar limnological and meteorologic conditions, as well as the similar sulphate concentrations.…”

“…, Pierce et al , 2022 (ref. 69)), including analysis for the available reduced inorganic sulphur species ( e.g. chromium reducible sulphur 92 ) that play an important role in understanding the relatively slow recovery of sulphur and mercury cycling in the sulphate-impacted lake.…”

Effects of Clearcutting and Residual Biomass Harvesting on Hillslope Mercury Mobilization and Downgradient Mercury Accumulation

“…Forestry operations often result in limited changes to SO 4 2− mobilization from uplands to lakes and rivers (Kronberg et al, 2016;Piirainen et al, 2004Piirainen et al, , 2009. However, small changes in SO 4 2− concentrations can have profound downgradient impacts on Hg cycling by fueling microbial SO 4 2− reduction and subsequent Hg methylation, particularly in peatlands (Branfireun et al, 1999;Mitchell et al, 2008aMitchell et al, , 2009Pierce et al, 2022). On these hillslopes, there was not a clear change in SO 4 2− concentration treatment ratios due to either harvesting practice but there was more inter-and intra-annual variability post-harvest.…”