十溴联苯醚污染土壤狼尾草根际消减特征及其作用机制研究

In accordance with the realistic meaning for remediation the soil polluted by poly brominated diphenyl ethers（PBDEs） and the deficiency in the research to phytoremediation and its rhizosphere coupling effect on PBDEs contaminated soil, combining decabromodiphenyl(BDE-209) as a representative PBDEs in PBDEs contaminated soil and the preliminary results that pennisetum has potential to rhizosphere remedy BDE-209 contaminated soil found by other research group, BDE-209 and pennisetum will be selected as contaminant ant plant objects in the present project, respectively. In accordance with the primary research result in plant rhizosphere phytoremediation to organic chemicals polluted soil and the efftcts of root exudate on pyene degradation and its mechamism, a hydroponic experiment, a indoor simulating cultivating experiment, a multi-interlayer rhizobox experiment and a rhizosphere simulating experiment will be combined to apply in the present project, to deeply probe into the components and its content in special root exudate of pennisetum which is response to BDE-209 stress, BDE-209 distribution charactertics after uptaking by pennisetum, solubilization effect to of pennisetum and its reaction mechanism, degradation effect to BDE-209 affected by enzyme in root exudate, spacial characteristics of BDE-209 degradation and relevant soil microorganism ecological evolvement with the different millimeter distance from the pennisetum root surface, and effects of pennisetum root exudate on BDE-209 degradation and relevant characteristics of soil microorganism ecological evolvement induced by pennisetum root exudate in the BDE-209 contaminated soil. Therefore, it will reveal the interactive relationship among special root exudate of pennisetum, soil microorganism ecological evolvement and the ecological chemical behavior of BDE-209, clarify the rhizosphere coupling system play a key role in self-purification process of BDE-209 contaminated soil and its eco-chemical mechanism, and clarify the extent of rhizosphere effect. At last, the results as above will improve the academic base and technical support in enriching and developing rhizoremediation technique to PBDEs and other organic compounds contaminated soil.

选择我国多溴联苯醚（PBDEs）污染土壤的主要成分十溴联苯醚和对其具有较强耐性和修复潜力的狼尾草为研究对象，综合采用水培、室内模拟、多隔层根箱培养和根际模拟等研究方法，深入探讨十溴联苯醚胁迫下狼尾草根系特异性分泌物组成和数量的响应，根系特异性分泌物对十溴联苯醚的增溶作用和机制及其酶对十溴联苯醚降解的作用，距离根表不同毫米级微域土壤中的十溴联苯醚特异空间消减规律和相应的土壤微生物学性状演替特征及狼尾草对十溴联苯醚的吸收分配特征，特异性根系分泌物对土壤中十溴联苯醚降解的影响及其相应诱导产生的土壤微生物学性状演替特征等，揭示狼尾草根际特异性根系分泌物、微生物学性状演替及根际十溴联苯醚消减行为之间的相互关系，阐明狼尾草根际效应响应特征对十溴联苯醚消减的作用及其生态化学机制，以期为丰富和发展土壤PBDEs污染的根际原位修复技术提供理论依据。

多溴联苯醚(PBDEs)是一类新持久性有机污染物，易在食物链中逐渐富集放大，使处于高位营养级的生物受到毒害，已成为相关研究热点。本项目重点探讨了狼尾草对BDE-209胁迫的根际效应响应特征对BDE-209消减的作用及其生态化学机制，主要结果如下：.土壤对BDE-209温吸附基本为线性，以分配机制为主导。BDE209污染胁迫下，狼尾草根系分泌物主要组分（低分子有机酸、总糖、氨基酸、酶）总体随BDE209胁迫浓度升高而显著上升，根系分泌物可抑制土壤对BD209的吸附，对BDE209具有明显的增溶作用，增溶贡献主要来自狼尾草系分泌物中大分子组分（>8000Da），其增溶效果是小分子根系分泌物9倍左右；根系中分泌的粗酶对BDE209具有降解作用，作用过程符合一级动力学方程，降解产物主要为低溴代的联苯醚，降解不彻底，其中硝酸根还原酶（NR）和谷胱甘肽S-转移酶（GST在脱溴降解过程中扮演着重要角色；狼尾草对BDE209污染有较强的耐受性，种植狼尾草可明显促进土壤中BDE209的降解，其机制主要是与植物的根际效应有关，与植物吸收积累无关。根际BDE209降解的整体趋势表现为：近根层>根生长层（根室）>远根层，其机制与土壤微生物随根际距离梯度的变化和微生物对根系分泌物剂量变化的响应高度一致。细菌随根系分泌物添加剂量的变化趋势与BDE209降解变化特征一致，表明BDE209的降解以细菌为主，意味着根系分泌物主要通过影响细菌群落的数量，进而影响着BDE209的降解变化特征。根际土细菌群落结构与环境因子冗余分析结果表明BDE209消减率与土壤DOC呈正相关，进一步证明狼尾草根系分泌物与土壤微生物（细菌）的互动关系是根际BDE209快速消减的核心生态机制。