水环境中亚硝胺前体物的微生物代谢来源机制假说的验证研究

N-Nitrosamines (NAs) are a group of carcinogenic emerging disinfection by-products (DBPs). They present high risk to drinking water safety in many regions around China due to high occurrence and concentration. The first key step to control NAs is to identify the sources of their precursors. However, the recent knowledge about that cannot explain the majority of NA precursor sources. The applicant first propose a hypothesis on NA precursor formation from microorganism metabolism in aquatic environment. The aim of this application for NSFC project is to verify this hypothesis..The main tasks for this project include: (1) Design and make the specific incubators for this microorganism metabolism study, add the representative individual amino acid as the sole substrates, then inoculate the typical pure bacteria strains or mixture. Monitor the NA formation potential during the incubation termly as well as other water quality parameters. (2) Choose those amino acids with high NA formation potential change during the incubation on task 1, purchase the 15N-labelled certain amino acids as the substrate, analyze the products during the incubation by GC/LC-MS-MS, TOF-MS. Then, the pathway of amino acids metabolism could be recognized and the mechanism of NA precursors could be determined. (3) This mechanism would be verified by the study of incubating real water samples with high amino acid concentration..The results of this project will verify the new formation mechanism of NA and precursors via microorganism metabolism. It will help assess the contribution of NAs and precursors from microorganism in real aquatic environment and guide the measure development to protect water safety.

亚硝胺是一类新兴消毒副产物，在我国不少地区的饮用水中被普遍检出且风险较高。控制亚硝胺首先要识别其前体物的来源。但是国内外现有研究只能解释亚硝胺前体物的部分来源。申请人首次提出了微生物代谢可能是水中亚硝胺前体物重要来源的假说。本申请的目的就是要验证这一假说。主要内容包括：1.设计加工微生物培养反应器，投加典型氨基酸作为底物，接种典型菌种或混合菌种，检测代谢过程中的亚硝胺生成潜能变化。2.选择内容1培养时有高亚硝胺潜能的氨基酸，采购15N同位素标记氨基酸作为底物，用气相/液相色谱串联质谱、飞行时间质谱等多种手段检测培养过程中的各种代谢成分，梳理氨基酸代谢过程中的反应途径，确定亚硝胺前体物的产生机制。3.选择氨基酸浓度高的实际水体，进行上述机制的验证。项目研究成果将证实微生物代谢生成亚硝胺前体物的新模式，有助于评估微生物代谢对实际水体中亚硝胺及其前体物的贡献，指导建立保护水质安全措施。

亚硝胺是一类强致癌物和新污染物，对人体健康有重要影响。自从20世纪末在北美地区饮用水中被发现以来，亚硝胺受到了国际水处理和水环境领域专家的高度关注。亚硝胺前体物的来源是当前亚硝胺领域的研究前沿和热点话题。本项目的研究目标如下：验证微生物代谢水中含氮物质生成亚硝胺前体物的假说，探索微生物代谢产生亚硝胺前体物的可能路径和环境条件影响，评估微生物代谢对实际水体中亚硝胺及其前体物生成的贡献水平。.在国家自然基金的资助下，项目组首次在国内外提出并验证了微生物代谢氨基酸类物质生成亚硝胺前体物的新机制；探索了微生物降解丙氨酸生成亚硝胺前体物的反应路径；根据文献数据，评估该机制平均可贡献我国水源水中约27-38%的NDMA生成潜能。项目组还首次开展了城市尺度的水中亚硝胺及其前体物的定量源解析工作，确定微生物代谢（约36%）、上游径流输送（21%）和当地污废水排放（17%）是该城市下游水源地中最重要的亚硝胺前体物来源；其中微生物代谢机制的贡献与此前根据文献数据评估结果非常吻合。.项目组提出的微生物代谢氨基酸生成亚硝胺新机制是在亚硝胺研究领域独立做出的引领性研究成果，可部分解释我国水源水中亚硝胺前体物浓度远高于欧美的原因，丰富了国际上对亚硝胺前体物主要来源的认识。该项目成果将为有关部门科学认识水中亚硝胺风险、加强水源地保护提供技术支撑，有助于提高我国供水安全水平。