含水层中1,2,3-三氯丙烷微生物降解机理的碳同位素标记

1,2,3-Trichloropropane（TCP）is an emerging persistent groundwater pollutant. A few laboratory studies indicate that TCP is biodegradable and mostly due to cometabolism, while there is no evidence of TCP degradation under complex field conditions being reported by now. In previous work, applicant has found carbon isotope evidences for TCP biodegradation in groundwater in one site. However, the species of TCP-degrading bacteria is still unclear as well as the degradation pathway. Taking the aquifer of the site as the research object and using the experimental techniques, this study is conducted through “field conceptual model-laboratory simulation experiment-field mechanism model” and both laboratory batch test and sand-box biodegradation simulation test are designed based on the identification of biogeochemical environment of TCP biodegradation in field, and the research is further bifurcated: On the one hand, treat isolation and characterization of TCP-Degrading bacteria as a breakthrough using culture method and high throughput sequencing technology, and assessment ecological effects as the main clue; on the other hand, treat growth substrate as a breakthrough using compound specific carbon isotope analysis, and identify degradation pathway as the main clue, meanwhile, obtain carbon isotope enrichment factor of TCP degradation, and label TCP degradation process. Both synthesized, the mechanism of TCP biodegradation is further analyzed. Combining with hydrogeological characteristics of the site, the transport and transformation processes of TCP in the aquifer will be revealed. This research will provide theoretical basis and technical support for the study conducted in the similar sites.

1,2,3-三氯丙烷（TCP）为地下水中新型持久性污染物，少量室内研究发现TCP可微生物降解且以共代谢为主，目前尚无野外复杂条件TCP降解的相关报道。申请人前期工作在某场地发现了地下水中TCP可微生物降解的碳同位素证据，但菌种及降解途径尚不清楚。本研究拟以该场地含水层为研究对象，以室内物理模拟为主要实验手段，采用“野外概念模型-室内模拟实验-野外机理模型”构建思路，以野外TCP微生物降解生物地球化学环境识别为基础，开展室内静态瓶装和动态砂箱微生物降解实验：一方面以培养法和高通量测序技术筛选鉴定TCP降解菌种为突破口，以生态效应评估为主线；另一方面以单体碳同位素确定生长基质为突破口，以降解途径识别为主线，同时，获取TCP降解碳同位素富集因子，标记TCP降解过程。两方面综合探讨TCP微生物降解机理。结合场地水文地质特征，解译含水层中TCP迁移转化过程，为类似场地研究提供理论依据和技术支持。

本研究通过对某典型氯代烃、苯系物污染场地的水文地质和污染资料的整理分析，识别了场地水文地质结构和地下水流场特征，刻画了污染分布特征，解析了场地污染来源；结合生物地球化学环境识别，构建了场地污染自然降解模型，并通过浓度、同位素空间变化及有机物间回归分析，提供了TCP自然降解及共代谢证据；在此基础上，模拟场地生物地球化学环境，设计了TCP共代谢降解室内微宇宙模拟试验，重点探究了微生物降解过程有机物及其碳稳定同位素分馏机制，建立典型苯系物共代谢降解TCP的碳稳定同位素分馏模型；进一步针对场地微生物修复的需求，广谱筛选TCP降解菌种SH-CL2，开展微生物微宇宙模拟实验，识别了绿色低成本TCP降解途径，首创构建了TCP代谢为3-氯丙烯的碳同位素瑞利分馏模型。.重要结果及关键数据如下：（1）典型场地同位素源解析：1,2-DCP和苯的δ13C0最负值-32.83‰、-28.87 ‰均位于DCJ2-2，是场地的污染源为主所在；（2）野外天然条件下TCP微生物降解同位素证据：硫酸盐、锰兼性厌氧还原（DO＜3.00 mg/L，ORP＜0 mV）生物地球化学环境条件下，TCP发生了极显著降解（δ13C＞2‰），场地井TCP的δ13C最大变幅5.38‰；（3）苯系物共代谢降解TCP的碳稳定同位素分馏模型：在有、无1,2-二氯丙烷DCP条件下，甲苯-TCP共代谢碳同位素分馏系数分别为0.6±0.4、3.1±0.5，其他苯系物无明显特征。（4）绿色低成本TCP降解途径及其同位素标记：以酵母浸粉和硫酸根为基质，将TCP依次代谢为3-氯丙烯、烯丙基硫醇的绿色低成本途径，其关键途径TCP代谢为3-氯丙烯，符合瑞利分馏模型，13C分馏富集系数ε=-5.7±0.7‰。