芦苇根际对有色溶解性有机质的脱色机理及环境行为

Decolorization mechanism and environmental behavior of colored dissolved organic matter in the rhizosphere of Phragmites australis

有色溶解性有机质(CDOM)是水体中天然有机质的重要组成成分,它的过量输入会造成湖泊、水库等水体的富营养化,甚至直接污染饮用水。植物修复技术具有经济有效、绿色环保等特点,适用于环境中CDOM面源污染的控制与治理以及污水处理厂尾水中CDOM的深度净化。研究植物净化过程中CDOM的脱色原理及环境行为,对水环境保护和饮用水安全具有十分重要的意义。通过CDOM在植物根际中的脱色、分布和组成分析,探究植物对CDOM的脱色性能以及CDOM在根际环境的分布特征和组成成分;结合植物根系分泌物和酶提取液的脱色实验,考察根系分泌物和植物酶对CDOM脱色反应的影响机制。结果表明:CDOM难以自然水解,其有效脱色依赖于植物的存在;植物对CDOM的作用方式以根系吸收为主、根表吸附为辅,形成了大部分CDOM以低分子形态累积在植物体内(92.2%)、少部分CDOM以高分子形态附着在植物表面(7.7%)的分布特征;植物根系分泌物虽然不能直接影响CDOM的脱色过程,但可以通过改善根际微环境、促进微生物生长、富集相关降解菌种、改变CDOM生物可利用性等方式来强化根际微生物对根表附着的高分子CDOM的碳源利用能力;经生物降解生成的低分子CDOM通过根系吸收进入植物体内,并在植物酶的作用下进一步代谢分解,从而达到植物净化CDOM的目的。

Colored dissolved organic matter(CDOM)is an important component of natural organic matter in water.CDOM with high concentrations may cause eutrophication of drinking water sources such as lakes and reservoirs,and even directly pollute municipal tap water.Phytoremediation is regarded as an effective,economical,and ecological technology for the treatment of CDOM non-point pollution,and the purification of CDOM polluted wastewater treatment plant discharge.For the sake of aquatic environmental protection and drinking water safety,it is very necessary to study the decolorization mechanism and environmental behavior of CDOM by plants.In the present study,the decolorization,distribution,and composition of CDOM in the rhizosphere of Phragmites australis were investigated,as well as the influence mechanism of plant root exudates and enzyme extracting solution on the CDOM removal.The results showed that CDOM was difficult to be hydrolyzed,and its effective decolorization depended on the effect of plants.In the rhizosphere,CDOM was mainly removed by plant uptake and supplemented by root adsorption,forming the distribution characteristics that most of the CDOM were accumulated by plants as low molecules(92.2%)and the rest were adhered to root surface as high molecules(7.7%).Although root exudates cannot directly affect the decolorization process of CDOM,they can enhance the carbon source utilization ability of rhizosphere microbes to the high molecular CDOM,by improving the rhizosphere microenvironment,promoting the microbial growth,enriching the related-degrading bacteria,and changing the CDOM bioavailability.Low molecular CDOM generated by microbial degradation was transported into the plant through root uptake,and then were metabolized under the effect of plant enzymes,so as to achieve the purpose of CDOM purification by plants.