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| Migration and transformation of roxarsone in the soil column and its risk assessment under continuous pollution |
| Received:November 22, 2022 Revised:February 08, 2023 |
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| KeyWord:roxarsone;continuous pollution;inorganic arsenic;migration and transformation;microbial diversity |
| Author Name | Affiliation | E-mail | | YANG Xuelei | Hebei Zhengrun Environmental Technology Co. Ltd, Shijiazhuang 050061, China | | | ZHAO Xinyi | Hebei Hydrology Engineering Geological Survey Institute Co. Ltd, Shijiazhuang 050061, China | | | LIU Yaci | Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang 050061, China
Fujian Provincial Key Laboratory of Water Cycling and Eco-Geological Processes, Xiamen 361000, China | liuyaci11@163.com |
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| Abstract: |
| Poultry waste is typically disposed in the open without seepage prevention, leading to the feed additive roxarsone（ROX） entering the environment and causing inorganic arsenic（As）pollution. In this study, 157-day one-dimensional soil column simulation was conducted to explore the spatial and temporal variations of As compound morphology and concentration in the vertical vadose zone under continuous ROX contamination. The microbial response at different depths was analyzed using high-throughput sequencing technology. The results showed that during the 157-day simulation of continuous ROX contamination, the degradation rate of ROX was very high, being significantly higher than the migration rate. The degradation and adsorption of ROX occurred in the shallow soil layer（0-10 cm）. ROX degradation products were mainly As（Ⅴ）and As（Ⅲ）, and the concentration of As（Ⅴ）was significantly higher than that of As（Ⅲ）, and As compounds were mainly clustered at a depth of 0-40 cm. The concentration of As compounds in soil was significantly higher than that in soil solution. Soil had a strong ability to fix As compounds, and the migration rate of As compounds was very slow. The maximum migration depth was 40 cm in 157 days, which showed that once the soil was contaminated by As, the long-term harm caused by its compounds was difficult to eliminate. The microbial community structure of surface soil differed significantly from that at other depths. Combined with RDA and PERMANOVA analysis, it was shown that depth and ROX concentration were the main factors controlling the microbial community diversity at different soil depths. The health risk assessment revealed that persistent ROX contamination in topsoil would lead to a major carcinogenic risk due to As. Therefore, it is recommended to fully implement regulations prohibiting the use of ROX. In countries and regions where the use of ROX is still allowed, it is necessary to strengthen the standardized treatment of livestock waste and avoid long-term accumulation in the open. |
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