Abstract：
Flooding of paddy fields during the rice growing season enhances arsenic (As) mobilization and greenhouse gas (e.g., methane) emissions. In this study, an adsorbent for dissolved organic matter (DOM), namely, activated carbon (AC), was applied to an arsenic-contaminated paddy soil. The capacity for simultaneously alleviating soil carbon emissions and As accumulation in rice grains was explored. Soil microcosm incubations and 2-year pot experimental results indicated that AC amendment significantly decreased porewater DOM, Fe(III) reduction/Fe2+ release, and As release. More importantly, soil carbon dioxide and methane emissions were mitigated in anoxic microcosm incubations. Porewater DOM of pot experiments mainly consisted of humic-like fluorophores with a molecular structure of lignins and tannins, which could mediate microbial reduction of Fe(III) (oxyhydr)oxides. Soil microcosm incubation experiments cospiking with a carbon source and AC further consolidated that DOM electron shuttling and microbial carbon source functions were crucial for soil Fe(III) reduction, thus driving paddy soil As release and carbon emission. Additionally, the application of AC alleviated rice grain dimethylarsenate accumulation over 2 years. Our results highlight the importance of microbial extracellular electron transfer in driving paddy soil anaerobic respiration and decreasing porewater DOM in simultaneously remediating As contamination and mitigating methane emission in paddy fields.
摘要：
水稻生长季节稻田的洪水增强了砷（As）的动员和温室气体（例如，甲烷)排放。在这项研究中,一种溶解有机物(DOM)的吸附剂，即,活性炭(AC),应用于砷污染的稻田土壤。探索了同时减轻土壤碳排放和水稻籽粒中砷积累的能力。土壤微观孵化和2年盆栽实验结果表明，AC改良剂显着降低了孔隙水DOM，Fe(III)还原/Fe2+释放,作为释放。更重要的是,土壤二氧化碳和甲烷的排放在缺氧的微观世界中得到了缓解。盆栽实验的PorewaterDOM主要由具有木质素和单宁分子结构的类腐殖质荧光团组成，它可以介导Fe（III）（氧化氢）氧化物的微生物还原。用碳源和AC进行的土壤微观世界孵化实验进一步巩固了DOM电子穿梭和微生物碳源功能对于土壤Fe（III）还原至关重要，从而驱动水稻土As释放和碳排放。此外,AC的应用缓解了水稻籽粒砷酸二甲酯的积累超过2年。我们的结果强调了微生物胞外电子转移在驱动稻田土壤厌氧呼吸和减少孔隙水DOM同时修复As污染和减少稻田甲烷排放中的重要性。
