Wen Mengtuo, Zhang Qiulan, Li Yasong, Cui Yali, Shao Jingli, Liu Yaci
School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China; Key Laboratory of Water and Soil Resources Conservation and Restoration in the Middle and Lower Reaches of Yellow River Basin, MNR, Zhengzhou, 450016, China; Fujian Provincial Key Laboratory of Water Cycling and Eco-Geological Processes, Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Xiamen, 361000, China.
School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
Chemosphere. 2024 Aug;362:142606. doi: 10.1016/j.chemosphere.2024.142606. Epub 2024 Jun 13.
Roxarsone (ROX), commonly employed as a livestock feed additive, largely remains unmetabolized and is subsequently excreted via feces. ROX could cause serious environmental risks due to its rapid transformation and high mobility in the anaerobic subsurface environment. Dissolved organic matter (DOM) is an important constituent of fecal organics in livestock waste and could affect the ROX biotransformation. Nonetheless, the underlying mechanisms governing the interaction between DOM and ROX biotransformation have not yet been elucidated in the anaerobic environment. In this study, the changes of ROX, metabolites, and microbial biomass in the solutions with varying DOM concentrations (0, 50, 100, 200, and 400 mg/L) under anaerobic environments were investigated during the ROX (200 mg/L) degradation. EEM-PARAFAC and metagenomic sequencing were combined to identify the dynamic shifts of DOM components and the functional microbial populations responsible for ROX degradation. Results indicated that DOM facilitated the anaerobic biotransformation of ROX and 200 mg/L ROX could be degraded completely in 28 h. The tryptophan-like within DOM functioned as a carbon source to promote the growth of microorganisms, thus accelerating the degradation of ROX. The mixed microflora involved in ROX anaerobic degrading contained genes associated with arsenic metabolism (arsR, arsC, acr3, arsA, nfnB, and arsB), and arsR, arsC, acr3 exhibited high microbial diversity. Variations in DOM concentrations significantly impacted the population dynamics of microorganisms involved in arsenic metabolism (Proteiniclasticum, Exiguobacterium, Clostridium, Proteiniphilum, Alkaliphilus, and Corynebacterium spp.), which in turn affected the transformation of ROX and its derivatives. This study reveals the mechanism of ROX degradation influenced by the varying concentrations of DOM under anaerobic environments, which is important for the prevention of arsenic contamination with elevated levels of organic matter.
洛克沙胂（ROX）通常用作牲畜饲料添加剂，大部分未被代谢，随后通过粪便排出。由于ROX在厌氧地下环境中快速转化且迁移性高，可能会导致严重的环境风险。溶解有机物（DOM）是畜禽粪便中有机物质的重要组成部分，可能会影响ROX的生物转化。然而，在厌氧环境中，DOM与ROX生物转化之间相互作用的潜在机制尚未阐明。本研究在ROX（200mg/L）降解过程中，研究了厌氧环境下不同DOM浓度（0、50、100、200和400mg/L）溶液中ROX、代谢产物和微生物生物量的变化。结合EEM-PARAFAC和宏基因组测序来确定DOM成分的动态变化以及负责ROX降解的功能微生物种群。结果表明，DOM促进了ROX的厌氧生物转化，200mg/L的ROX可在28小时内完全降解。DOM中的类色氨酸作为碳源促进微生物生长，从而加速ROX的降解。参与ROX厌氧降解的混合微生物群包含与砷代谢相关的基因（arsR、arsC、acr3、arsA、nfnB和arsB），且arsR、arsC、acr3表现出较高的微生物多样性。DOM浓度的变化显著影响参与砷代谢的微生物（解朊菌属、微小杆菌属、梭菌属、嗜蛋白菌属、嗜碱菌属和棒杆菌属）的种群动态，进而影响ROX及其衍生物的转化。本研究揭示了厌氧环境下不同浓度DOM影响ROX降解的机制，这对于预防高有机质水平下的砷污染具有重要意义。
