Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310000, China.
Department of Environmental Health and Management, Health Services Academy, Islamabad 44000, Pakistan.
Sci Total Environ. 2024 Nov 25;953:176167. doi: 10.1016/j.scitotenv.2024.176167. Epub 2024 Sep 10.
Flooding of paddy fields enhances methane (CH) emissions and arsenic (As) mobilisation, which are crucial issues for agricultural greenhouse gas emissions and food safety. Birnessite (δ-MnO) is a common natural oxidant and scavenger for heavy metals. In this study, birnessite was applied to As-contaminated paddy soil. The capacity for simultaneously alleviating CH emissions and As mobility was explored. Soil microcosm incubation results indicated that birnessite addition simultaneously reduced CH emissions by 47 %-54 % and As release by 38 %-85 %. The addition of birnessite decreased the dissolved organic carbon (DOC) contents and altered its chemical properties. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) results showed that birnessite reduced the labile fractions of proteins, carbohydrates, lignins, tannins, and unsaturated hydrocarbons, however, increased the abundance of condensed aromatic structures, suggesting the polymerisation of dissolved organic matter (DOM) by birnessite. The degradation of labile fractions and the polymerisation of DOM resulted in an inventory of recalcitrant DOM, which is difficult for microbes to metabolise, thus inhibiting methanogenesis. In contrast, birnessite addition increased CH oxidation, as the particulate methane monooxygenase (pmoA) gene abundance increased by 30 %. The enhanced polymerisation of DOM by birnessite also increased As complexation with organics, leading to the transfer of As to the organic bound phase. In addition, the decrease in ferrous ion [Fe(II)] concentrations with birnessite indicated that the reductive dissolution of Fe oxides was suppressed, which limited the release of arsenite [As(III)] under reducing conditions. Furthermore, birnessite decreased As methylation and shaped the soil microbial community structure by enriching the metal-reducing bacterium Bacillus. Overall, our results provide a promising method to suppress greenhouse gas emissions and the risk of As contamination in paddy soils, although further studies are needed to verify its efficacy and effectiveness under field conditions.
稻田淹水会增加甲烷（CH）排放和砷（As）的迁移，这是农业温室气体排放和食品安全的关键问题。钠锰矿（δ-MnO）是一种常见的天然氧化剂和重金属清除剂。本研究将钠锰矿应用于砷污染稻田土壤，探索其同时缓解 CH 排放和 As 迁移的能力。土壤微宇宙培养结果表明，添加钠锰矿可同时减少 CH 排放 47%-54%和 As 释放 38%-85%。添加钠锰矿降低了溶解性有机碳（DOC）含量并改变了其化学性质。傅里叶变换离子回旋共振质谱（FT-ICR-MS）结果表明，钠锰矿降低了蛋白质、碳水化合物、木质素、单宁和不饱和烃的可利用分数，而增加了缩合芳香结构的丰度，表明钠锰矿对溶解有机质（DOM）的聚合。可利用分数的降解和 DOM 的聚合导致了难降解 DOM 的积累，这使得微生物难以代谢，从而抑制了甲烷生成。相比之下，添加钠锰矿增加了 CH 氧化，颗粒态甲烷单加氧酶（pmoA）基因丰度增加了 30%。钠锰矿对 DOM 的增强聚合也增加了 As 与有机物的络合，导致 As 向有机结合相转移。此外，由于钠锰矿降低了二价铁离子[Fe（II）]浓度，抑制了铁氧化物的还原溶解，从而限制了在还原条件下砷酸根[As（III）]的释放。此外，钠锰矿减少了 As 的甲基化，并通过富集金属还原菌芽孢杆菌来塑造土壤微生物群落结构。总的来说，我们的研究结果为抑制温室气体排放和降低稻田土壤中 As 污染风险提供了一种有前景的方法，尽管还需要进一步的研究来验证其在田间条件下的效果和有效性。
