人工湿地典型植物的根际效应对六氯苯生物降解的影响机制研究

The effective degradation of Hexachlorobenzene (HCB) is a hot issue of common concern in environmental science and ecology. This project is based on our early results which indicate that constructed wetlands (CWs) can eliminate considerable amounts of HCB residues transported from agricultural fields and other potentially contaminated soil and rhizosphere microbial degradation is the main process.However, the lack of knowledge on degradation mechanism and degradation pathway of HCB in rhizosphere of CWs hampers the efforts to transfer phytoremediation results from labs to field sites. We plan to choose Phragmites australis or Typha latifolia as the typical macrophytes in CWs for mesocosms wetlands, investigate the reductive and oxidative dechlorination of HCB and its homologous compound in rhizosphere and non-rhizosphere and analyze the relative roles of dominant ecological factors, quantitative rhizosphere exudates and rhizosphere microorganisms in the process of HCB degradation by alternating cycles of flooding (to induce anaerobic conditions) and no-flooding (aerobic conditions) in mesocosms. Moreover, the chemical compositions and concentrations of dechlorinated products of HCB in rhizosphere soil and non-rhizosphere soil will be analyzed to elucidate the pathways of HCB dechlorination under the action of rhizosphere effect, thus to reveal the HCB degradation mechanisms for controlling HCB in the future. The project will provide possible solutions for high efficient degradation of HCB and serve as a reference for biodegradation of other related POPs (Persistent Organic Pollutants).

持久性有机污染物（POPs）六氯苯（Hexachlorobenzene，简称HCB）的有效降解是环境科学及生态学普遍关注的热点问题。基于本团队前期研究发现，人工湿地是一种能够高效降解HCB的生物处理方法，根际微生物降解是主要过程，但是HCB在人工湿地植物根际的降解机制及降解途径尚不清楚，从而限制了人工湿地在HCB污染防控中的应用。为此，本项目选择典型人工湿地植物普通芦苇和宽叶香蒲，构建湿地微宇宙系统，通过间歇式淹没法模拟不同溶解氧条件，研究HCB及其同系物在根际与非根际环境中的降解效能及其主要影响因子，并确定根系分泌物及根际微生物在HCB降解过程中的相对作用，进而依据降解中间产物的类型和浓度变化，确定HCB的生物降解途径，阐明HCB在人工湿地根际中的降解机制，以期探寻HCB污染防治的新途径。本项目将为HCB的高效降解提供理论依据和技术支持，也可为其它相关POPs的生物降解提供借鉴。

如何有效去除环境介质中的持久性有机污染物六氯苯（Hexachlorobenzene，HCB）已成为全球关注热点。本项目聚焦于人工湿地两种植物根际效应对HCB降解的影响，试验得出的主要结论如下：(1) 营养液水培试验证明了香蒲促进低浓度六氯苯的根际降解，厚壁菌门（Firmicutes）和变形菌门（Proteobacteria）是根际细菌的主要门类，且芽孢杆菌属对HCB污染适应性最强；(2) 以全球分布最广、运用最多的普通芦苇（Phragmites australis）和宽叶香蒲（Typha latifolia）为人工湿地典型植物，构建湿地微宇宙系统，根箱隔层分区法验证了根际细菌是生物降解HCB的“主力菌”，其群落结构及多样性影响湿地系统对HCB的降解效应，而厚壁菌门（芽孢杆菌属）是HCB污染湿地土壤的优势细菌；(3) PCR-DGGE与构建克隆文库表明，植物种类和污染胁迫均可调控根际微生物的变化，种植香蒲根际微生物丰富度高于芦苇，根际效应大，能够广泛应用于去除低浓度HCB污染；(4) 厌氧-好氧生物降解法促进高氯代污染物的去除，影响HCB降解的根际效应主要表现为与土壤脱氢酶和多酚氧化酶活性呈显著负相关关系，与根系分泌物相关性不明显；(5) 16S rDNA高通量测序分析贫富营养化水体中不同浓度HCB胁迫下，香蒲根系生物膜中细菌群落组成结构，发现细菌优势菌为变形菌门、放线菌门、蓝藻门、绿弯菌门。本项目发表SCI论文4篇，中文核心期刊论文8篇，2项实用新型专利获授权，培养硕士研究生1名。