Mercury contamination is a global concern, and the degradation and detoxification of methylmercury have gained significant attention due to its neurotoxicity and biomagnification within the food chain. However, the currently known pathways of abiotic demethylation are limited to light-induced photodegradation process and little is known about light-independent abiotic demethylation of methylmercury. In this study, we reported a novel abiotic pathway for the degradation of methylmercury through the oxidation of both mineral structural iron(II) and surface-adsorbed iron(II) in the absence of light. Our findings reveal that methylmercury can be oxidatively degraded by reactive oxygen species, specifically hydroxyl and superoxide radicals, which are generated from the oxidation of iron(II) minerals under dark conditions. Surprisingly, Hg(0) trapping experiments demonstrated that inorganic Hg(II) resulting from the oxidative degradation of methylmercury was rapidly reduced to gaseous Hg(0) by iron(II) minerals. The demethylation of methylmercury, coupled with the generation of Hg(0), suggests a potential natural attenuation process for methylmercury. Our results highlight the underappreciated roles of iron(II) minerals in the abiotic degradation of methylmercury and the release of gaseous Hg(0) into the atmosphere.

中文翻译：

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通过铁 (II) 矿物的氧化将甲基汞降解为 Hg(0)

汞污染是一个全球性问题，甲基汞的降解和解毒因其在食物链中的神经毒性和生物放大作用而受到广泛关注。然而，目前已知的非生物去甲基化途径仅限于光诱导的光降解过程，并且对甲基汞的光不依赖的非生物去甲基化知之甚少。在这项研究中，我们报道了一种新的非生物途径，通过在没有光的情况下氧化矿物结构铁 (II) 和表面吸附铁 (II) 来降解甲基汞。我们的研究结果表明，甲基汞可以被活性氧（特别是羟基和超氧自由基）氧化降解，这些自由基是铁（II）矿物在黑暗条件下氧化产生的。令人惊讶的是，Hg(​​0)捕获实验表明，甲基汞氧化降解产生的无机Hg(II)被铁(II)矿物迅速还原为气态Hg(0)。甲基汞的去甲基化与 Hg(0) 的产生相结合，表明甲基汞存在潜在的自然衰减过程。我们的研究结果强调了铁 (II) 矿物质在甲基汞非生物降解和气态 Hg(0) 释放到大气中的作用未被充分认识。