School of Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, China.
Faculty of Sciences and Technology, Civil Engineering Research and Innovation for Sustainability Center, University of Algarve, Faro, Portugal.
Sci Total Environ. 2024 Jun 1;927:172335. doi: 10.1016/j.scitotenv.2024.172335. Epub 2024 Apr 9.
The neurotoxic methylmercury (MeHg) is a product of inorganic mercury (IHg) after microbial transformation. Yet it remains unclear whether microbial activity or IHg supply dominates Hg methylation in paddies, hotspots of MeHg formation. Here, we quantified the response of MeHg production to changes in microbial activity and Hg supply using 63 paddy soils under the common scenario of straw amendment, a globally prevalent agricultural practice. We demonstrate that the IHg supply is the limiting factor for Hg methylation in paddies. This is because IHg supply is generally low in soils and can largely be facilitated (by 336-747 %) by straw amendment. The generally high activities of sulfate-reducing bacteria (SRB) do not limit Hg methylation, even though SRB have been validated as the predominant microbial Hg methylators in paddies in this study. These findings caution against the mobilization of legacy Hg triggered by human activities and climate change, resulting in increased MeHg production and the subsequent flux of this potent neurotoxin to our dining tables.
神经毒性甲基汞（MeHg）是无机汞（IHg）经微生物转化后的产物。然而，在汞甲基化的热点——稻田中，究竟是微生物活性还是 IHg 供应主导着 Hg 甲基化过程仍不清楚。在这里，我们使用 63 种在普遍存在的农业实践——秸秆添加的情况下的稻田土壤，定量研究了微生物活性和 Hg 供应变化对 MeHg 生成的响应。结果表明，在稻田中，Hg 甲基化受到 IHg 供应的限制。这是因为土壤中的 IHg 供应普遍较低，而秸秆添加可大大促进（336-747%）Hg 甲基化。尽管硫酸盐还原菌（SRB）已被验证为本研究中稻田中主要的微生物 Hg 甲基化菌，但它们的高活性并不限制 Hg 甲基化。这些发现告诫人们要注意人类活动和气候变化引发的历史汞的迁移，这可能导致 MeHg 生成增加，并随后将这种强效神经毒素输送到我们的餐桌上。
