Mercury-contaminated sediment and water contain various Hg species, with a small fraction available for microbial conversion to the bioaccumulative neurotoxin monomethylmercury (MeHg). Quantification of this available Hg pool is needed to prioritize sites for risk management. This study compared the efficacy of diffusive gradient in thin-film (DGT) passive samplers to a thiol-based selective extraction method with glutathione (GSH) and conventional filtration (<0.2 μm) as indicators of Hg bioavailability. Anaerobic sediment slurry microcosms were amended with isotopically labeled inorganic Hg "endmembers" (dissolved Hg2+, Hg-humic acid, Hg-sorbed to FeS, HgS nanoparticles) with a known range of bioavailability and methylation potentials. Net MeHg production (expressed as percent of total Hg as MeHg) over 1 week correlated with mass accumulation of Hg endmembers on the DGTs and only sometimes correlated with the 0.2 μm filter passing Hg fraction and the GSH-extractable Hg fraction. These results suggest for the first time that inorganic Hg uptake in DGTs may indicate bioavailability for methylating microbes. Moreover, the methylating microbial community assessed by hgcA gene abundance was not always consistent with methylation rates between the experiments, indicating that knowledge of the methylating community should target the transcript or protein level. Altogether, these results suggest that DGTs could be used to quantify the bioavailable Hg fraction as part of a method to assess net MeHg production potential in the environment.

中文翻译：

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在薄膜采样器中使用扩散梯度对甲基化的汞生物利用度进行定量。

汞污染的沉积物和水中含有多种汞，其中一小部分可用于微生物转化为生物蓄积性神经毒素单甲基汞（MeHg）。需要对该可用汞池进行量化，以对风险管理站点进行优先级排序。这项研究将薄膜（DGT）被动采样器中扩散梯度的效果与基于谷胱甘肽（GSH）和常规过滤（<0.2μm）作为汞生物利用度指标的基于硫醇的选择性萃取方法进行了比较。用已知范围的生物利用度和甲基化潜力，用同位素标记的无机Hg“末端成员”（溶解的Hg2 +，Hg腐植酸，Hg吸附到FeS上的HgS纳米颗粒）修正厌氧沉积物泥浆的微观世界。1周内的净MeHg产量（表示为总Hg占MeHg的百分比）与DGT上Hg末端成员的质量积累相关，并且有时仅与0.2μm过滤器通过的Hg分数和可从GSH提取的Hg分数相关。这些结果首次表明，DGT中无机汞的吸收可能表明甲基化微生物的生物利用度。此外，通过hgcA基因丰度评估的甲基化微生物群落并不总是与实验之间的甲基化速率相一致，这表明甲基化群落的知识应针对转录本或蛋白质水平。总而言之，这些结果表明，DGT可以作为量化环境中净MeHg产生潜力的方法的一部分，可以用来量化生物可利用的Hg分数。