砷挥发是砷生物地球化学大循环的驱动力，同时在砷污染环境修复方面表现出很大的应用潜力。可溶性有机质（DOM）作为有机质中相对活跃的组分，显著影响着土壤中砷的迁移、转化及微生物区系，但其对土壤微生物介导砷挥发的影响及分子机制目前尚不明确。本项目拟采用气体流动装置对挥发态砷进行捕获，分析添加不同来源DOM后土壤中砷挥发量差异，探讨土壤理化因子变化影响砷挥发的可能机理；利用实时定量PCR及高通量测序等技术，从分子生物学水平揭示添加DOM后土壤微生物群落结构变化、砷甲基化功能基因丰度变化影响砷甲基化进程的相关机制；利用13C同位素示踪及基于同步辐射的X射线吸收近边结构光谱与扩展边X射线吸收精细结构光谱，探讨源自DOM的甲基对微生物甲基化砷的贡献，从分子水平证实砷与碳的成键并揭示相关机制。研究结果有助于阐明砷生物地球化学大循环的微生物驱动机制，对今后砷污染土壤的微生物挥发修复亦具有重要的科学意义。

Arsenic (As) volatilization drives the biogeochemical circle of As, and also shows great potential to remediate As-contaminated environment. Dissolved organic matter (DOM) as the active components of organic matter can significantly change the mobility and speciation of As and the micro flora in soils. However, little information of DOM affecting As volatilization conducted by soil microorganisms and its related mechanisms is available. In this project, air-flowing device will be used to trap volatile arsenide. The effects of different sourced DOM on As volatilization will be analyzed and the possible mechanisms of soil physicochemical factors influencing As volatilization will also be explored. By employing real-time fluorescent quantitative PCR and high-throughput sequencing, the microbial community structure and the abundance of functional genes capable As reduction and methylation in soils after spiking with DOM will be determined and the relative mechanisms will be unclosed. Furthermore, with the use of 13C isotopic tracing and the synchrotron based X-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), the contribution of methyl from DOM to As methylation in soils will be studied and the possible molecular mechanisms of As binding carbon in the trapped volatile arsenide will be uncovered. The observations of this project will be conducive to understanding the microbial driving mechanisms of As biogeochemical circle, and also will shed light on the future remediation of As-contaminated soils using microorganisms.