Anhui Normal University
Supported by the National Natural Science Foundation of China (no. 41807117）, the Project Incubation Foundation of Anhui Normal University (No. 2022xjxm049) and the Project of Innovation and Entrepreneurship Training for College Students (no. S202210370320)
二苯砷酸（diphenylarsinic acid，DPAA）是含砷化学武器在环境中的主要降解产物之一，研究铁还原和硫酸盐还原对土壤中DPAA释放与硫化的影响对于深入认识DPAA的环境地球化学行为至关重要。考察了在淹水和添加不同浓度乳酸钠（C）和硫酸钠（S）培养时花生地和林地红壤中DPAA的释放与硫化情况，并分析铁还原和硫酸盐还原的影响。结果显示：（1）对花生地而言，与不添加硫酸钠和乳酸钠（S-C-）以及仅添加硫酸钠（S+C-）的处理相比，同时添加硫酸钠和乳酸钠（1 300 μg·g-1（以C计，下同），S+C+；2 170 μg·g-1，S+C++）的处理中DPAA释放明显增强，这与乳酸钠促进了铁还原（>45%）从而有利于DPAA的释放有关；（2）在花生地的S+C+处理中硫酸盐还原最为显著（13周时溶解态硫化物浓度为11.28 mg·L-1），DPAA的去除率（59.6%）最高且主要发生硫化，而在S+C++处理中铁还原程度的增加和硫酸盐还原程度的降低不利于DPAA的硫化；（3）与花生地不同，无论是否添加乳酸钠和硫酸盐，林地中未见DPAA的释放与硫化现象，这与其铁还原程度较低（<25%）和硫酸盐未发生还原（未检测到溶解态硫化物）有关；（4）与林地相比，花生地中梭菌属、芽孢杆菌属和脱硫芽孢杆菌属的丰度明显增加，这很可能分别促进了铁还原和硫酸盐还原，最终对DPAA释放和硫化产生了更显著的影响。总体上，与铁还原促进DPAA的释放和进一步的硫化相比，硫酸盐的还原程度以及溶液相中硫化物的浓度很可能是控制淹水红壤中DPAA硫化的一个更重要的因素。研究结果将为深入认识DPAA的环境行为和发展DPAA污染红壤的生物刺激修复技术提供理论基础。
【Objective】Diphenylarsinic acid (DPAA) is one of the main degradation products of arsenic-containing chemical weapons in the environment. The objective of this study was to investigate the effects of iron and sulfate reduction on the mobilization and thionation of DPAA in soil.【Method】Acrisol from a peanut field and woodland were selected for soil incubation experiment, and both were spiked with DPAA and different concentrations of sodium lactate (C source) and sodium sulfate (S source) under flooded condition. Four treatments were established in the current study, treatment one (S-C-) was created without the addition of S or C sources, treatment two (S+C-) only received 426 μg·g-1 S, treatment three (S+C+) received 426 μg·g-1 S and 1 300 μg·g-1 C, and treatment four (S+C++) received 426 μg·g-1 S and 2 170 μg·g-1 C. Samples of the soil and supernatant were collected for the analysis of DPAA, Fe2+, HCl-extractable Fe2+, SO42-, sulfide, pH, Eh and bacterial community structure.【Result】Results for the peanut field indicated that the mobilization of DPAA was significantly enhanced in the S+C+ and S+C++ treatments due to the addition of carbon, as compared to S-C- and S+C- treatments without carbon. This difference was likely caused by the elevated Fe reduction (> 45%) due to lactate addition, which then promoted DPAA mobilization. In comparison to other treatments, sulfate reduction was most significant in the S+C+ treatment of the peanut field (with the concentration of dissolved sulfide reaching 11.28 mg·L-1 after 13 weeks of incubation), where the removal rate (59.6%) of DPAA was the highest and DPAA was primarily thionated. However, the increased Fe reduction and decreased sulfate reduction in the S+C++ treatment were not conducive to the thionation of DPAA. Unlike peanut land, the mobilization and thionation of DPAA were not observed in woodland regardless of the addition of sodium lactate and sulfate. This difference can be explained by the lower degree of Fe reduction (< 25%) and the absence of sulfate reduction (without the detection of dissolved sulfide) in woodland. The relative abundances of Clostridium, Bacillus and Desulfosporosinus were significantly higher in the peanut field soil when compared to woodland. This probably promoted the occurrence of iron and sulfate reduction, respectively, and both processes ultimately had a stronger influence on the mobilization and thionation of DPAA.【Conclusion】Generally, instead of the stimulating effect of Fe reduction on DPAA mobilization, the degree of sulfate reduction and the concentration of sulfide in the liquid phase is a more significant factor in determining DPAA thionaiton in Acrisol under flooded condition. The findings will serve as a theoretical foundation for the in-depth understanding of the environmental behavior of DPAA as well as the development of biostimulation remediation solutions for DPAA-contaminated Acrisol.
Zhu Meng, He Yuhuan, Wei Xiaobao, Li Yuan, Yang Ruyi. Effects of iron and sulfate reduction on the mobilization and thionation of diphenylarsinic acid in Acrisol[J]. Acta Pedologica Sinica,,[In Press]