养殖区有机质高异常包气带中洛克沙胂的迁移转化机理研究

The poultry feed additive of roxarsone (3-nitro-4-hydroxyphenylarsonic acid) is accumulated in poultry feces, and the accumulation of poultry feces in the open air all year round leads to the significantly higher concentration of organic matter in the shallow vadose zone than the natural conditions. Studies showed that organic matter could affect the adsorption and degradation rate of roxarsone. However, it’s still unclear that the mechanism of roxarsone migration and microbial transformation under the condition of high anomaly of organic matter. This study takes the vadose zone with high anomaly of organic matter as the research object, bases on the site environmental condition recognition, the contrast experiment of roxarsone biotransformation and soil column migration will be carried on. On the one hand, roxarsone degradation bacteria will be isolated and identified by traditional culture and high-throughput sequencing technology, and the effect of organic matter on roxarsone biotransformation will be evaluated. On the other hand, one-dimensional soil column will be used to simulate the migration and transformation process of roxarsone. The key layers of morphological transformation, adsorption and aggregation of roxarsone, and the temporal-spatial evolution of microbial community structure and function are analyzed. Both synthesized with correction through field monitoring, the migration and transformation mechanism of roxarsone in the vadose zone with high anomaly of organic matter are studied. The results will provide scientific evidence for revealing the potential connection between open air accumulation of poultry feces and arsenic pollution in groundwater.

禽畜饲料添加剂3-硝基-4-羟基苯胂酸（洛克沙胂）大量累积于禽畜粪便中，同时禽畜粪便常年的露天堆积导致浅层包气带有机质浓度显著高于天然条件，已有研究显示有机质会影响洛克沙胂的吸附以及降解速率。但有机质高异常条件下，包气带中洛克沙胂的迁移和微生物转化机理尚不清楚。因此，本研究拟以有机质高异常的包气带为研究对象，在场地环境条件识别的基础上，进行洛克沙胂生物转化特征和土柱迁移的对比实验。一方面通过传统培养法和高通量测序技术筛选鉴定洛克沙胂降解菌，评估有机质对洛克沙胂生物转化的影响；另一方面利用一维土柱模拟洛克沙胂的迁移转化过程，研究其形态转化、吸附聚集的关键层位，分析微生物群落结构及其功能的时空演化。两方面综合探讨高有机质包气带中洛克沙胂的迁移转化机理，并通过野外监测进行修正，为揭示禽畜粪便露天堆积与地下水砷污染的潜在联系提供科学依据。

洛克沙胂（3-硝基-4-羟基苯胂酸，ROX）被广泛用作禽畜饲料添加剂，在微生物作用下转化为毒性较高的无机砷，ROX与粪便中的高有机质共同迁移至包气带中，然而目前对有机质高异常包气带中ROX的生物转化机理尚不清楚。通过研究溶解性有机质（DOM）对ROX环境行为影响发现：DOM可以显著促进ROX降解，当DOM浓度较高(≥200mg/kg)时，ROX在2天内即可降解完全，由于中间产物3-氨基-4-羟基苯胂酸（HAPA）的难降解，使得最终降解产物无机砷浓度呈缓慢上升态势；微生物多样性与DOM浓度、ROX降解速率呈负相关，不同DOM浓度的优势物种不同；砷化合物对土壤中微生物群落的影响程度为HAPA>ROX>As(Ⅲ)>As(V)。厌氧条件下，ROX的添加促进微生物的生长，微生物反过来促进ROX的降解；DOM通过提供碳源促进微生物生长，同时增加ROX的溶解度以提高其生物利用度。通过不同DOM含量条件下ROX迁移转化的土柱模拟发现：添加DOM会影响砷化合物在不同层位的含量、种类和分布，这是由DOM-微生物-砷化合物三者之间相互影响和作用所致。本研究揭示了DOM-微生物-ROX三者之间相互作用的关系，展示了有机质高异常包气带中ROX的迁移转化过程，这对于自然条件下土壤砷污染的防治具有重要意义。