再生水回补河湖入渗地下水过程中糖皮质激素的迁移转化规律及调控机制研究

About ten billions cubic meters of reclaimed water was recharged into groundwater by river- and lake-based reuse every year. When using reclaimed water for natural recharging groundwater, glucocorticoids pollution might be a potential threat to underground aquifers because the migration, biotransformation and fate of glucocorticoids in the natural groundwater recharge process are unclear. The glucocorticoids can induce ecological harm by interfering with the endocrine system at extremely low concentrations when these chemicals infiltrate into groundwater. Therefore, the glucocorticoids might pose a potential threat to the quality of drinking water as well as groundwater. Thus, the present study will first develop chemical analysis methods for identifying these glucocorticoids compounds and their biological metabolic intermediates by using advanced UPLC-QTOF-MS and UPLC-MS/MS technology combined with the solid phase extraction process, the microorganism analysis methods for microbial community structure and the function of gene expression by metagenomic and metatranscriptomic. Secondly, the absorption-desorption kinetics and mechanism of glucocorticoids onto the different soil aquifer media will be revealed. Thirdly, the biotransformation pathways, mechanism and influencing factors will be proposed by identifying the intermediate metabolite products, the changes in microbial community structure and the function of gene expression under the recharge condition changing from aerobic to anaerobic. Finally, these results can be used to predict the types and distribution levels about glucocorticoids and their metabolites fate occurring in different recharge mode and different types of soil and aquifer, and explore the relation between the adsorption and transformation behavior during natural groundwater recharge process. The results obtained from this work will help to understand of glucocorticoids accumulation in natural groundwater recharge areas under different recharging conditions, to facilitate the prediction of the fate of glucocorticoids in underground aquifers, and to provide scientific basis for risk assessment and pollution control in the environment.

我国每年有约数百亿立方米的再生水通过河湖回补途径自然入渗地下水，但再生水中的糖皮质激素在入渗地下水过程中的迁移转化规律、降解机理和归宿尚不清楚。本项目拟采用高精度UPLC-QTOF-MS化学分析手段、宏基因组测序和宏转录的微生物鉴别方法，构建再生水补给地下水过程中由好氧、缺氧向厌氧环境过度的模拟系统，结合自然入渗现场长期跟踪监测，研究不同补给模式和不同包气带土壤介质类型下，糖皮质激素在包气带土壤层及地下含水层中的吸附、迁移、生物降解及最终归趋，阐明吸附-解析和生物降解耦合作用下微生物群落结构演替及功能基因表达差异对糖皮质激素的降解机理及代谢途径的影响；建立糖皮质激素在地下水中的迁移转化动力学模型，揭示不同补给条件下糖皮质激素的赋存种类、形态及其时空分布差异和影响因素；构建三维数学溶质运移模型预测其在土壤和地下水中迁移转化，定性和定量评价再生水入渗地下水过程中糖皮质激素对土壤和地下水的影响。

近年来，糖皮质激素类（GCs）内分泌干扰物在水环境中的检出频率持续增加，而其引发的水环境和水生态问题却知之甚少。本项目针对再生水大规模河湖利用入渗地下水过程中痕量GCs对地下水的影响开展，首先对地表水中GCs的浓度进行检测，选出检出频率较高的天然糖皮质激素氢化可的松、可的松和泼尼松，以及浓度较高的人工合成糖皮质激素曲安奈德、地塞米松作为研究对象；其次对它们在不同土壤介质中的自然衰减规律进行研究，探明它们的吸附解析热力学、微生物群落结构变化及代谢途径；最后，在自然衰减的基础上，开发构建了复合河床阻控污染物入渗系统和生物电化学强化去除系统，通过构建三维数学溶质运移模型预测其在土壤和地下水中的迁移转化。. 通过吸附解吸的拟合结果显示天然GCs解吸滞后性小于人工合成GCs，且在壤质沙土的吸附解吸滞后性最强，随着GCs浓度浓度的升高，解吸更难发生；生物降解实验结果表明，含卤素GCs的代谢途径主要包括脱卤、水解、脱羧、氧化、开环、裂解等，在这一过程中Pseudomonas, Desulfuromonas, Methylotenera等降解菌的相对丰度提高，脱卤基因的拷贝数增加。. 开发构建了复合河床阻控污染物入渗系统和生物电化学强化去除系统，通过提高生物降解速率，促进还原脱卤微生物的富集，达到对再生水入渗过程中GCs的强化去除效果。. 以天然水体中GCs的浓度为基础，通过实验室土柱淋溶模拟实验得到GCs在不同包气带土壤类型下的衰减速率为壤土>粉砂质壤土>沙壤土，且干湿交替优于连续淋溶模式。污染物在包气带和地下水中的迁移转化模型表明自然衰减情况下，60d后包气带底部渗出浓度接近入渗浓度；对距污染源不同距离和时间的地下水中TA浓度进行预测，结果表明10年后510m处地下水中TA浓度为3.138×10-5 ng/L。此项研究研究成果可望对再生水深度利用过程中痕量有毒有害有机污染物的防控和地下水保护提供重要基础数据。