水体中典型非甾体抗炎药类污染物在微生物降解过程中的毒性变化与机理

Being more and more frequently detected in the aquatic environment, non-steroidal anti-inflammatory drugs (NSAIDs) designed to alleviate pain for humanity have become a new concern for environmental protection. Even at lower concentrations, NSAIDs might cause adverse impact on aquatic organisms with different trophic levels. What’s worse, NSAIDs may also been biodegraded and transformed into different kinds of toxic metabolites by diverse microorganisms, whose potential risks can not be ignored. Thence, for more accurate and comprehensive assessment of their environmental risks, both the ecological toxicity and microbial degradation mechanisms of NSAIDs should be taken into consideration and paid more attention to. The objectives of the current project which comprises a three-tier experimental design were 1) to analyze the metabolites of NSAIDs produced at different stages of microbial degradation, for better understand of their biodegradation pathways; 2) to evaluate the acute and chronic toxicity of NSAIDs and their metabolites using bioassay battery with different kinds of aquatic organisms, for better understand of the joint toxicity of these co-exist contaminants in aquatic systems; 3) to investigate the mechanisms involved in the microbial degradation of NSAIDs, by changing the biodegradation conditions and comparing theirs effects on the microbial community structures, degradation capacities, different composition of NSAIDs and metabolites, as well as their joint toxicities. The results illustrated in this project would be useful for further study on the biodegradation and toxicity assessment of NSAIDs.

广泛使用的非甾体抗炎药物（non-steroidal antiinflammatory drugs, NSAIDs）在为人类减轻病痛的同时，也带来诸多环境污染和危害，不仅较低浓度水平暴露时会对水生态系统中各营养级生物造成不良影响，而且还可能通过微生物的降解作用产生一系列具有不同毒性效应的中间和末端的代谢产物，潜在风险不容忽视。然而，迄今针对这类污染物在微生物介导条件下的生态毒理研究工作尚未开展。本项目拟将微生物降解转化特点研究与生态毒性效应评估紧密结合，通过测定NSAIDs的微生物降解速率及产物组成，了解其微生物降解特点；并借助不同营养级模式生物的成组生物毒性试验，对这类污染物及其降解产物的毒性效应进行评估，阐明毒性变化规律和联合作用类型（相加、协同和拮抗等）；最后综合对比不同环境条件下微生物群落结构和降解能力的动态变化，以及NSAIDs在不同降解阶段的产物组成与毒性的变化情况，探讨影响这类污染物微生物降解脱毒特性的关键因素，阐明微生物介导下NSAIDs的生态毒性变化规律及相关机理。相关研究成果将为水环境中NSAIDs的潜在生态毒性风险预测与评估提供科学参考数据。

非甾体抗炎药原本是用来促进或抑制人体某些生理功能，从而减轻或消除病痛。然而，随着个人和畜牧业的大量、频繁使用，近年来这类新型污染物越来越频繁地在环境中被检出，带来诸多环境污染和危害，潜在风险不容忽视。项目采用多种快速生物降解和固有生物降解性试验体系研究了双氯芬酸、醋氨酚、布洛芬的生物降解性，及其对发光细菌、藻类、大型溞和斑马鱼的毒性，开展了斑马鱼胚胎抗氧化酶受胁迫效应评估，研究了降解产物的生物毒性和对微生物酶活及群落功能多样性的影响。醋氨酚比双氯芬酸和布洛芬更易被微生物降解。在抗炎药暴露下发光细菌的荧光强度明显受到抑制。双氯芬酸、醋氨酚和布洛芬对发光细菌荧光强度半数抑制效应浓度分别为1.03、1.47和1.82 mg/L。双氯芬酸和布洛芬对羊角月牙藻的72 h EC10分别为92.0 mg/L、75.6 mg/L。醋氨酚对羊角月牙藻的72 h EC10大于100 mg/L，毒性最低。抗炎药单独存在时对大型溞产生明显的急慢性毒性，且其浓度的改变也会对幼溞存活率、死亡时间、脱壳时间、脱壳总数、怀卵时间、怀卵总数、产溞总数和体长等产生不同程度的抑制作用，各效应终点参数敏感性强弱也表现出一致趋势，繁殖情况最敏感，生长情况次之，存活情况最不敏感。毒性最强的双氯芬酸可导致斑马鱼胚胎产生明显的尾折、脊柱弯曲、心包囊肿和卵黄囊肿等非致死性现象，及卵凝结和胚胎死亡等致死性现象，最高浓度100%致畸致死。抗炎药对几种模式生物的胁迫作用呈现出明显的“浓度-效应”关系和“时间-效应”关系。此外，非甾体抗炎药暴露下，斑马鱼胚胎也受到明显的氧化应激胁迫，导致了活性氧自由基等氧化物质的积累，并由此对这些抗氧化酶产生了进一步的抑制作用。抗炎药无论单独暴露还是二元混存暴露均对活性污泥的酶活具有抑制作用，不同浓度的抗炎药对酶活有不同程度影响，同时也影响了活性污泥中微生物酶活，并降低了群落功能多样性。非甾体抗炎药混存时化合物之间可能存在着协同作用而使其毒性增强。