Abstract:

The migration and transformation processes of arsenic (As) in soil affect As accumulation in rice, which posing a threat to human health. These processes are determined by As speciation in the soil and are related to soil physicochemical properties and soil microorganisms. To effectively control As pollution in soil, it is necessary to understand the physicochemical and biochemical behaviors of As in soil, including its redox reactions, methylation processes, and adsorption characteristics on mineral surfaces. This study systematically discusses the effects and key regulatory mechanisms of water management practices, iron mineral composition, nitrogen cycling, and organic matter (primarily humic substances) on As migration and transformation. Intermittent irrigation can effectively inhibit As release under anaerobic conditions, thereby reducing the As content in rice grains. The iron layer on root surfaces acts as an important “natural barrier,” and its stability is affected by mineral crystallinity and microbial iron reduction. Ammonium nitrogen oxidation promotes As activation, whereas nitrate nitrogen, through anaerobic oxidation of As(Ⅲ) coupled with iron oxidation, can inactivate arsenic. Humic substances, as electron donors or shuttles, can stimulate microbial iron and As reduction processes, increasing the concentration of active As in soil solution, thus posing potential risks. To effectively reduce As accumulation and ensure the safety of agricultural products, research should shift from single-factor studies to multi-factor interactions, establishing a multidisciplinary research framework encompassing soil environmental chemistry, microbiology, and plant physiology. This approach will allow for the precise identification of the physicochemical and microbial mechanisms of As transformation, optimization of green remediation technologies, and ultimately, regional-scale As pollution risk prediction and intelligent management of As-contaminated environments.

Key words: arsenic, paddy soil, iron minerals, organic matter, NO₃^--N

摘要：

土壤砷的迁移转化过程影响水稻砷累积，进而危害人体健康。该过程由土壤砷的赋存形态决定，与土壤的理化性质及土壤微生物等因素有关。开展定向土壤砷污染防控，需明晰砷在土壤中的物理化学和生物化学行为，包括砷的氧化还原和甲基化过程及其在矿物相中的吸附特性。该文系统探讨了水分管理措施、铁矿物成分、氮循环过程及有机质（主要以腐殖质为例）对砷迁移转化过程的制约效应及其关键调控机制：间歇灌溉可有效抑制厌氧条件下砷的释放，降低稻米籽粒中的砷含量；根表铁膜作为重要的“天然屏障”，其稳定性受矿物结晶度和微生物铁还原作用影响；铵态氮氧化促进砷的活化，而硝态氮则通过驱动As(Ⅲ)的厌氧氧化并与铁氧化作用耦合，从而实现对砷的钝化；腐殖质作为电子供体或电子穿梭体，可刺激微生物铁还原和砷还原过程，增加土壤溶液中活性砷的浓度，从而存在潜在风险。为有效降低砷积累、保障农产品的安全生产，提出应从单一因子提升至多因子作用影响研究，构建“土壤环境化学-微生物学-植物生理学”的多学科交叉研究链条，精准识别砷转化的物理化学机制及微生物分子机制，优化绿色调控技术，实现区域尺度砷污染风险预测与智慧管控。

关键词: 砷, 水稻土, 铁矿物, 有机质, 硝态氮