Monomethylmercury (MMHg) is a potent neurotoxin that poses a threat to human health. MMHg cycles in all spheres of the Earth but the sources and fate of atmospheric MMHg are unclear. Here, we develop a global model for atmospheric MMHg, which integrates the presently available data and indicates the limitations of the current study. Constrained by the observations in the atmosphere, the global atmospheric MMHg from all sources is 1009 (205–2474 as an uncertainty range) Mg/yr, with the largest sources from the in-cloud methylation of divalent mercury (475 Mg/yr) and MMHg sea spray (395 Mg/yr). MMHg has a short lifetime of 1.9 days in the troposphere due to rapid photo-demethylation. Our model indicates a net loss of marine MMHg to the atmosphere and thus a detoxifying effect on MMHg contamination in marine fish. However, it suggests additional MMHg deposition to the land, particularly in densely populated coastal areas, introducing a new risk pathway that needs to be considered in mercury exposure assessment. The atmosphere plays a non-negligible role in the biogeochemical cycle and human health, which requires further study and consideration in implementing the global Minamata Convention.

中文翻译：

---

大气中的一甲基汞：受观测限制的推断来源和对人类暴露的影响


一甲基汞 （MMHg） 是一种对人类健康构成威胁的强效神经毒素。MMHg 在地球的所有球体中都存在循环，但大气中 MMHg 的来源和归宿尚不清楚。在这里，我们开发了一个大气 MMHg 的全球模型，它整合了目前可用的数据并指出了当前研究的局限性。受大气观测的限制，所有来源的全球大气MMHg为1009（不确定范围为205-2474）毫克/年，其中最大的来源来自二价汞的云内甲基化（475 Mg/yr）和MMHg海喷雾（395 Mg/yr）。由于快速的光去甲基化，MMHg 在对流层中的寿命很短，只有 1.9 天。我们的模型表明海洋 MMHg 净损失到大气中，因此对海洋鱼类中的 MMHg 污染有解毒作用。然而，报告建议将 MMHg 额外沉积到土地中，特别是在人口稠密的沿海地区，这引入了一种新的风险途径，需要在汞暴露评估中予以考虑。大气在生物地球化学循环和人类健康中起着不可忽视的作用，在实施全球水俣公约时需要进一步研究和考虑。