沉水植物及其附生生物对水体中常见内分泌干扰物的降解转化

Endocrine disruptors like nonylphenol (NP) and bisphenol A (BPA) are frequently detected in water column all around the world. Submerged macrophytes and the associated epiphytes are found to have great ability in removing NP and BPA from the water column, therefore greatly affect the environmental fate of the pollution. Biodegradation and biotransformation are supposed to be dominant in the removal of NP and BPA from the environment. In this research, eight species of common native submerged plants are selected for the tests. Mechanisms involving in biodegradation and biotransformation of NP and BPA by these plants are to be investigated under aseptic conditions. Related enzymes in the biodegradation will be determined. Contribution of biodegradation and biotransformation to the removal by plants will be also calculated. The resulting metabolites of NP and BPA should be determined by C-14 isotops addition and analyses, together with the analyses using GC-MS and LC-MS. At the same time, epiphytes of those plants are to be investigated in their contribution in removing NP and BPA from water column. Mechanisms involving in the biodegradation and biotransformation will be also tested, and the resulting products shall be also determined. Bacteria and fungi in the epiphytes responsible for the biodegradation and biotransformation are to be identified according to the analyses of comparable variation in community compositions using RFLP based on 16S rRNA and 18S rRNA, respectively. Microalgae responsive for the biodegradation and biotransformation will also be identified according to analyses of the variation in community compositions. Finally, this research will be also greatly beneficial to the application of submerged plants and their epiphytes to the phytoremediation of water ecosystems polluted by NP and BPA.

壬基酚（NP）和双酚A（BPA）是水体中最常检测出的两类内分泌干扰物。沉水植物-附生生物能去除该类污染物，其生物降解转化可能是主要途径。研究沉水植物及其附生生物对水体中NP和BPA的降解转化，对阐明该类污染物的环境归趋有重要意义。本研究采用常见的8种沉水植物，以无菌苗为材料研究其对NP和BPA的降解转化机制和效率，确定有关的降解酶类，并通过C-14同位素技术结合GC-MS和LC-MS检测鉴定降解转化产物。同时，研究附生生物群落对NP和BPA的降解转化机制和效率，鉴定产物，后通过基于16S rRNA的RFLP技术分析其附生细菌群落多样性并鉴定主要降解细菌，基于18S rRNA的RFLP技术分析附生真菌群落多样性并鉴定主要降解真菌，同时分析附生藻类群落多样性并鉴定主要的具降解转化作用的藻类。本研究结果也可水体中该类污染物的植物修复应用提供理论依据。

本研究选取两种常见内分泌干扰物BPA和NP为对象，研究沉水植物体系的降解效率，并揭示内在机理。结果发现，多数沉水植物对这两种污染物具有较强的降解转化能力，可在12 d和8 d内去除90%以上的BPA和NP，附生细菌贡献小，在BPA去除过程中小于15%，在NP降解转化过程中无贡献。植物体内不会对这两种污染物有高的生物积累。所以利用沉水植物修复该类污染水体，既稳定高效又减少其环境危害。选择高效物种金鱼藻和狐尾藻，建立无菌苗培养体系后，进一步研究植物本身对这两种污染物的降解转化机制。利用LC-MS/MS和GC-MS分析植物对BPA的降解转化产物，发现3个可能产物，包括p-hydroxyacetophenone，protocatechuate和BPA-OH，后者为中间产物，据此推断可能的降解途径。通过处理前后植物酶活的变化，结合提取粗酶降解体系必须添加双氧水才高效降解的结果，认为过氧化物酶可能在植物降解BPA过程中起重要作用。事实上，对BPA具有更高效降解能力的轮叶黑藻无菌苗中过氧化物酶活性显著高于降解能力较低的野生苗。利用16s rDNA的高通量测序分析金鱼藻和狐尾藻附生细菌群落在添加BPA前后变化，发现金鱼藻中Gammaproteobacteria ，Flavobacteriia和Chloroplast相对丰度显著增加，狐尾藻中Alphaproteobacteria和Clostridia相对丰度显著增加，这些细菌可能与BPA降解相关。植物对NP的降解转化产物分析及对NP具有降解转化能力的主要附生细菌研究仍在进行中。BPA和NP处理均不会显著改变植物附生藻类群落构成，表明附生藻类对污染物去除影响较小。同时，本研究还探索了自然水体中BPA的去除因素，发现光解和水体微生物的作用小，沉积物则会通过吸附和生物降解转化作用较多去除水中BPA，利用无菌苗可高效快速修复BPA污染水体，特别是金鱼藻。通过BPA和NP的富集分离筛选后，并未发现高效降解附生细菌。综上结果，BPA及NP的环境归趋在沉水植物体系中主要归因于植物的作用，应重点关注植物的降解转化过程、机制及产物，此结论尚未见报道。本研究发表论文1篇，另有5篇文章待投（4篇SCI+1篇中文核心），直接培养博士生1名，硕士生1名。