Conventional approaches for in situ remediation of mercury (Hg)-contaminated soils and sediments rely mostly on precipitation or adsorption. However, this can generate Hg-rich surfaces that facilitate microbial production of methylmercury (MeHg), a potent, bioaccumulative neurotoxin. Herein, we prove the concept that the risk of mercury methylation can be effectively minimized by adding sulfur-intercalated layered double hydroxide (S-LDH) to Hg-contaminated soils. Hg bound to S-LDH has minimal methylation potential when incubated with model methylating bacteria Pseudodesulfovibrio mercurii ND132 and Geobacter sulfurreducens PCA. With a combination of spectroscopic and microscopic evidence, as well as theoretical calculations, we confirm that dissolved Hg(II) tends to enter the interlayers of S-LDH to bind to the sulfur groups intercalated within, leading to the formation of nanoscale metacinnabar (β-HgS). This not only physically blocks the contact of methylating microorganisms but also inhibits secondary release of bound mercury in the presence of strong binding ligands in porewater. This study highlights the promising concept of in situ risk reduction of heavy metal contamination by inducing precipitation within (nano)confined domains, achieving a sustainable outcome of enhanced removal and reduced bioaccessibility for pollutants that may otherwise be bioavailable in the form of nanoprecipitates.

中文翻译：

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硫插层双氢氧化物可最大限度地减少微生物汞甲基化：对汞污染场地原位修复的影响


原位修复受汞 (Hg) 污染的土壤和沉积物的传统方法主要依靠沉淀或吸附。然而，这会产生富含汞的表面，促进微生物产生甲基汞（MeHg），这是一种强效的生物累积性神经毒素。在此，我们证明了通过向汞污染土壤中添加硫插层状双氢氧化物（S-LDH）可以有效降低汞甲基化风险的概念。当与模型甲基化细菌Pseudodesulfovibrio Mercurii ND132 和Geobactersulfurreducens PCA 一起孵育时，与 S-LDH 结合的 Hg 具有最小的甲基化潜力。结合光谱和显微证据以及理论计算，我们证实溶解的 Hg(II) 倾向于进入 S-LDH 的层间，与嵌入其中的硫基团结合，从而形成纳米级的元朱砂 (β -HgS）。这不仅物理上阻止了甲基化微生物的接触，而且在孔隙水中存在强结合配体的情况下抑制了结合汞的二次释放。这项研究强调了通过在（纳米）有限域内诱导沉淀来原位降低重金属污染风险的有前途的概念，从而实现增强去除和降低污染物生物可及性的可持续结果，否则这些污染物可能以纳米沉淀物的形式被生物利用。