土壤中硫酸盐还原菌介导的铁还原对二苯砷酸释放与降解过程的耦合机制

Soil is a complicated biotic and abiotic system with multiple media and interfaces. The environmental behavior of organic pollutants in the soil was involved in a variety of chemical and biological processes. It has been an important frontier issue in the field of international environmental science and soil remediation technology to explore the mechanisms of microbial-mediated oxidation and reduction, combining and releasing, transformation and degradation processes of organic pollutants in the soil. Diphenylarsinic acid (DPAA), an emerging issue of global concern related to abandoned chemical warfare agents, is selected as target pollutant to conduct this study. The integrated use of advanced spectrographic and chromatographic techniques such as X- ray absorption spectroscopy and high performance liquid chromatography - tandem mass spectrometry and other modern techniques are to be applied to study the following three aspects mediated by sulfate reducing bacteria (SRB): (1) the adsorption - desorption kinetics and coordination mechanism of DPAA with different iron oxides; (2) binding characterizations and releasing dynamics of DPAA on particle surfaces of different soils; (3) anaerobic biodegradation pathways and metabolic intermediates of DPAA. The results of the study will be helpful to reveal the mechanisms of DPAA anaerobic biodegradation coupled to the reduction of iron and sulfate mediated by SRB in the soil, which will provide the theoretical basis and technical principles for bioremediation of organoarsenic polluted soils in the regions with abandoned chemical weapons in China.

土壤是一个多介质、多界面、生命与非生命体系交叉的复杂系统。有机污染物在土壤中的环境行为涉及多种土壤化学与生物学过程。研究微生物介导下，有机污染物在土壤中的氧化与还原、结合与释放、转化与降解等过程的耦合机制是国际环境科学与土壤修复研究领域的前沿重要课题。本项目选择近年来国际上广泛关注的含砷化学武器遗留地区土壤中的有机砷化物二苯砷酸为目标污染物，综合运用X-射线吸收光谱和高效液相色谱-串联质谱等现代光学与色谱学分析技术，重点研究硫酸盐还原菌介导的铁还原条件下，不同铁矿物对二苯砷酸的吸附-解吸动力学与分子键合特征、二苯砷酸在不同类型土壤颗粒表面的结合形态与释放动态、硫酸盐还原菌对二苯砷酸的厌氧降解途径与代谢产物等，旨在揭示硫酸盐还原菌介导的二苯砷酸厌氧生物降解过程与硫酸盐还原、铁还原等化学过程之间的耦合机理，为我国化学武器遗留地区有机砷污染土壤的生物修复提供理论依据与技术原理。

二苯砷酸（Diphenylarsinic acid，DPAA）是化学武器掩埋区土壤中最主要的有机砷污染物之一。硫酸盐还原菌是土壤中一类活跃的微生物，可催化土壤中的硫酸盐还原等多个氧化还原反应。本项目以针铁矿、水铁矿、赤铁矿等3种铁氧化物以及红壤和黑土2种不同类型土壤为对象，研究硫酸盐还原菌介导的铁还原对土壤和铁氧化物中二苯砷酸释放与降解过程的耦合机制。研究结果表明：DPAA在3种铁矿物上生成的内圈层络合物主要为双齿双核结构，As-Fe键的原子间距为3.19-3.33 Å。土壤中的氧化物，尤其是非晶质铁氧化物在土壤吸附DPAA过程中发挥了极为重要的作用。接种硫酸盐还原菌Clostridium sp. SRB-2可通过促进体系中的硫酸盐还原生成具有较高还原活性的硫化物，使铁氧化物溶液体系和土壤体系中的铁氧化物发生还原性溶解，进而导致铁氧化物或土壤固相表面吸附的DPAA大量释放至溶液环境中。释放后的DPAA可被硫酸盐还原菌进一步厌氧代谢转化为二苯基硫代砷酸（DPTAA）。对硫酸盐还原菌SRB-2菌株的全基因组扫描完成图分析表明，SRB-2基因组内含有多个参与硫酸盐还原、砷转运、砷酸还原以及砷抗性的功能基因。研究结果可为我国化学武器埋藏区有机砷污染土壤的生物修复提供理论依据与技术原理。