DOM influences Hg methylation in paddy soils across a Hg contamination gradient

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

“…Therefore, this artisanal Hg mining site was selected for examining soil–atmosphere Hg(0) flux exchanges. The average total Hg and MeHg concentrations in paddy soils were 17.2 ± 1.7 mg kg –1 and 2.42 ± 1.6 μg kg –1 , respectively. , The average soil organic matter in the paddy soils was 8 ± 1.2% . The average pH of the paddy soils was 7.0 ± 0.6, which is comparable to or even lower than that in the higher Hg-contaminated soil (7.2 ± 0.8) or the background soil (7.4 ± 0.2) from different locations in China .…”

“…37 The average pH of the paddy soils was 7.0 ± 0.6, 37 which is comparable to or even lower than that in the higher Hg-contaminated soil (7.2 ± 0.8) or the background soil (7.4 ± 0.2) from different locations in China. 37 The redox potential measured under flooded conditions in the rice paddy was 106.0 ± 26.3 mV.…”

“…The average total Hg and MeHg concentrations in paddy soils were 17.2 ± 1.7 mg kg –1 and 2.42 ± 1.6 μg kg –1 , respectively. , The average soil organic matter in the paddy soils was 8 ± 1.2% . The average pH of the paddy soils was 7.0 ± 0.6, which is comparable to or even lower than that in the higher Hg-contaminated soil (7.2 ± 0.8) or the background soil (7.4 ± 0.2) from different locations in China . The redox potential measured under flooded conditions in the rice paddy was 106.0 ± 26.3 mV.…”

Dissolved organic matter fosters core mercury-methylating microbiome for methylmercury production in paddy soils

“…THg concentrations in paddy soils ranged from 0.03 to 1079.75 μg/g dw (Table S1). As reported in our previous study, dividing paddy soils by THg concentration rather than sampling sites facilitates a comprehensive investigation of the key factors influencing Hg methylation (Abdelhafiz et al, 2023). Therefore, the paddy soils in this study were divided into three categories according to THg concentration: non-Hg contaminated soils (NMS, with average levels of 0.24 ± 0.18 μg/g dw, n=23), moderate Hg-contaminated soils (MMS, 18.28 ± 6.77 μg/g dw, n=13), and high Hg-contaminated soils (HMS, 637.79 ± 160.93 μg/g dw, n=10).…”

“…As a result, the role of paddy soil DOM on Hg methylation remains elusive. Our recent study showed a significant and strong relationship between MeHg production and lower molecular weight DOM in paddy soils collected from major rice-producing areas across China (Abdelhafiz et al, 2023). Given paddy soil DOM's significant chemodiversity (Li et al, 2018), it is reasonable to hypothesize that the effect of DOM on MeHg production cannot be assessed solely based on Hg speciation and bioavailability, suggesting that other factors also play a role in MeHg production.…”