红树林湿地生物修复多溴联苯醚（PBDEs）的根际功能及氮效应研究

Toxic, recalcitrant and newly emerged organic pollutants such as polybrominated diphenyl ethers (PBDEs) are common contaminants in coastal sediments, and their carcinogenic properties have led to increasing attention on their remediation. The most significant phytoremediation process for organic pollutants such as PBDEs is in the root zone environment (the rhizosphere), which called rhizosphere degradation. Mangroves are unique wetland systems along the coastline of tropical and subtropical regions and are often affected by human activities. Substantial amounts of toxic organic pollutants including PBDEs are found in mangrove wetland. Mangroves are subject to tidal flushing with alternating aerobic and anaerobic environments thus favor both aerobic and anaerobic reductive transformation/degradation of PBDEs. Wetland plants are also known to transfer oxygen from the above-ground tissue to the roots for internal respiration. Excess oxygen is released to the rhizosphere to provide aerobic pockets and influence the degradation of pollutants and the formation of iron plaque, which could immobilize pollutants on root surface and uptake. Due to its close proximity to human, mangrove wetland also receives excess nitrogen (N) from municipal, industrial and agricultural discharge. As nitrogen is known to promote plant and microbial growth, N addition may also affect the uptake and degradation of toxic organic pollutants. However, the roles of rhizosphere and N effects on the degradation of PBDEs by wetland plants, such as mangroves, and associated microorganisms have never been explored. The proposed study therefore aims to investigate the significance of rhizosphere and N on the remvoal and degradation of PBDEs, including the effects of roots of different mangrove plants in releasing oxygen to create an aerobic environment in the rhizosphere, the formation of iron plaque on root surface, the roles of root exudates and sediments on the degradation, mobility, bioavailability of PBDEs, and the effects of N addition on these processes. The results from this proposed work will provide a thorough scientific understanding on the significance and mechanisms of mangrove plants, rhizopshere and sediment in the degradation of PBDEs, and develop a posible protocol for the bioremediation of PBDE-contaminated environment.

多溴联苯醚（PBDEs）是海岸沉积物新型的有毒持久性有机污染物。红树林位于河口海岸潮间带，深受人类活动影响而成为累积场所。PBDEs修复手段日益受到关注，特别是植物根际降解。周期性的潮水涨落形成有氧和厌氧交替环境，为PBDEs有氧和厌氧降解提供必要条件。过量氧气经呼吸作用从地上组织传输到根系，释放形成有氧根际环境和根系铁膜而影响PBDEs的降解和固定作用。红树林同时受到过量的不同氮源输入。外源氮通过促进植物及微生物的生长，而影响有机污染物的吸收和降解。然而，红树植物根际功能和氮效应对PBDEs降解研究尚未开展。因此，本项目拟探讨比较不同红树植物的根系泌氧、铁膜形成、分泌物及沉积物对PBDEs降解和迁移转运的作用机理；同时，探讨上述过程对氮输入的响应机制。本研究结果将揭示红树植物根际和沉积物的PBDEs降解机理，及其相应的氮效应，为建立红树林湿地生物修复PBDEs污染提供科学理论依据。

红树林湿地是南方河口与滨海重要的生态系统，特别在经济发达的粤港澳大湾区背景下，湿地生态系统承受各类污染物的胁迫，其中，持久性有机污染物多溴联苯醚（PBDEs）是一种典型的有毒有害的新型污染物。本项目研究了PBDEs在红树林湿地的分布迁移、污染生态机理以及影响因素的研究，进一步探索建立了生物修复PBDEs的方法。本研究在顺利完成项目目标的基础上，拓展PBDEs污染物相关研究方向，比如PBDEs与微塑料污染的相互关系，取得阶段性成果。本项目顺利完成，研究成果为进一步综合了解红树林湿地污染生态学及其相关环境管理提供理论依据。