Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2025 Feb;148:468-475. doi: 10.1016/j.jes.2023.10.030. Epub 2023 Oct 31.
Arsenic (As) methylation in soils affects the environmental behavior of As, excessive accumulation of dimethylarsenate (DMA) in rice plants leads to straighthead disease and a serious drop in crop yield. Understanding the mobility and transformation of methylated arsenic in redox-changing paddy fields is crucial for food security. Here, soils including un-arsenic contaminated (N-As), low-arsenic (L-As), medium-arsenic (M-As), and high-arsenic (H-As) soils were incubated under continuous anoxic, continuous oxic, and consecutive anoxic/oxic treatments respectively, to profile arsenic methylating process and microbial species involved in the As cycle. Under anoxic-oxic (A-O) treatment, methylated arsenic was significantly increased once oxygen was introduced into the incubation system. The methylated arsenic concentrations were up to 2-24 times higher than those in anoxic (A), oxic (O), and oxic-anoxic (O-A) treatments, under which arsenic was methylated slightly and then decreased in all four As concentration soils. In fact, the most plentiful arsenite S-adenosylmethionine methyltransferase genes (arsM) contributed to the increase in As methylation. Proteobacteria (40.8%-62.4%), Firmicutes (3.5%-15.7%), and Desulfobacterota (5.3%-13.3%) were the major microorganisms related to this process. These microbial increased markedly and played more important roles after oxygen was introduced, indicating that they were potential keystone microbial groups for As methylation in the alternating anoxic (flooding) and oxic (drainage) environment. The novel findings provided new insights into the reoxidation-driven arsenic methylation processes and the model could be used for further risk estimation in periodically flooded paddy fields.
土壤中砷的甲基化会影响砷的环境行为，水稻植株中二甲砷酸酯（DMA）的过度积累会导致直头病和作物产量的严重下降。了解氧化还原变化稻田中甲基化砷的迁移转化对于粮食安全至关重要。在这里，分别在连续缺氧、连续有氧和连续缺氧/有氧处理下培养了包括未砷污染（N-As）、低砷（L-As）、中砷（M-As）和高砷（H-As）土壤，以分析砷甲基化过程和参与砷循环的微生物种类。在缺氧-好氧（A-O）处理下，一旦向培养系统中引入氧气，甲基化砷就会显著增加。在所有四种砷浓度土壤中，甲基化砷浓度比缺氧（A）、好氧（O）和好氧-缺氧（O-A）处理高 2-24 倍，在这些处理中，砷的甲基化程度较低，然后逐渐减少。事实上，丰度最高的亚砷酸盐 S-腺苷甲硫氨酸甲基转移酶基因（arsM）促进了砷的甲基化。变形菌门（40.8%-62.4%）、厚壁菌门（3.5%-15.7%）和脱硫杆菌门（5.3%-13.3%）是与这一过程相关的主要微生物。这些微生物在引入氧气后显著增加，并发挥了更重要的作用，表明它们是交替缺氧（淹没）和好氧（排水）环境中砷甲基化的潜在关键微生物群。这些新发现为再氧化驱动的砷甲基化过程提供了新的见解，该模型可用于周期性淹没稻田中的进一步风险评估。
