秸秆源溶解有机质对典型有机污染物光降解的调控作用及机制

Straw-derived dissolved organic matter (DOM), to a certain extent, may regulate the photodegradation of organic pollutants (OPs) in farmland water environment. However, previous researches mainly focused on the effects of dissolved humic acid and fulvic acid, and neglected the photochemical effects of straw-derived DOM on OPs photodegradation. Therefore, in this research, the DOM derived from wheat and rice straw are used to study the effects and mechanisms in regulating the photodegradation of diuron, sulfamethoxazole and 17β-estradiol in pure water, dissolved humic acid and fulvic acid solutions. Here, the major research focus is the influence of the interactions between the straw-derived DOM and dissolved humic acid and fulvic acid on the photodegradation of OPs. Taking multiple methods, this study will obtain the photodegradation characteristics of OPs regulated by the two straw-derived DOM. Correlative and quantitative models are built between the photodegradation rate of the OPs and the components, structures and properties of the two straw-derived DOM. Based on these models, the primary components, structures and properties responsible for the DOM regulating OPs photodegradation may be identified. The dominant mechanisms are individually addressed and quantified for the photodegradation of OPs regulated by the two straw-derived DOM. Furthermore, a systematic investigation will be carried out to investigate the effects of light intensity, pH, DO and other environment factors on these dominant mechanisms. Results of this research will extend our knowledge on the photochemical effects of straw-derived DOM in the environment, and provide the basis for predicting the photochemical fate of OPs in farmland water environment and others.

秸秆源溶解有机质（DOM）在一定程度上调控着农田水环境中有机污染物（OPs）的光降解，但以往的研究集中于溶解胡敏酸和富里酸，而忽视了秸秆源DOM对OPs光降解的调控作用。本申请拟以小麦和水稻秸秆源DOM为对象，研究其对敌草隆、磺胺甲恶唑和17β-雌二醇在纯水、溶解胡敏酸和富里酸溶液中光降解的调控，重点关注秸秆源DOM与溶解胡敏酸和富里酸相互作用对OPs光降解的影响。采用多种研究手段，掌握OPs在秸秆源DOM调控作用下的光降解特征；通过构建OPs光降解速率与秸秆源DOM组成、结构和性质的相关性及定量预测模型，锁定起调控作用的核心组分、结构和性质；阐明秸秆源DOM调控OPs光降解的主导机制，并量化各主导机制的贡献；系统考察光照强度、pH和DO等对秸秆源DOM调控OPs光降解机制的影响。本研究将推动对秸秆源DOM环境光化学效应的认识，并为农田等水环境中OPs的光化学归趋预测提供依据。

秸秆源溶解有机质（DOM）是农田水生态系统中DOM的重要组成部分，在一定程度上调控着农田水环境中有机污染物的光降解，但目前对秸秆源DOM调控有机污染物光降解的过程及机制并不清楚。本项目以小麦和水稻秸秆源DOM为代表，以室内模拟与田间实际样品调查相结合的方式，切合农田水环境条件，采用稳态光降解、活性物种淬灭、光谱分析、理论计算与模型拟合等手段研究了秸秆源DOM的释放过程及特征，秸秆源DOM对有机污染物光降解的影响，以及秸秆源DOM对溶解胡敏酸和富里酸诱导有机污染物光降解过程的调控作用及机制，完成了项目预期目标。在完成项目的前提下，项目组针对研究过程中发现的新问题，将研究内容进行了有效扩展。研究发现：（1）秸秆源DOM由类色氨酸、类酪氨酸和类富里酸组成，其理化特征与秸秆的分解程度和种类有关；秸秆源DOM中的类色氨酸和类酪氨酸具有一定的光化学活性。（2）类富里酸是秸秆源DOM促进敌草隆和17β-雌二醇光降解的主导组分，而类色氨酸是秸秆源DOM促进磺胺甲恶唑光降解的主导组分；秸秆源DOM对有机污染物光降解的调控作用可由其紫外光谱指数和荧光特征组分丰度预测，其调控机制主要涉及光生羟基、单线态氧和三线态秸秆源DOM。（3）秸秆源DOM主要通过类色氨酸组分与溶解胡敏酸和富里酸发生结合作用，从而削弱溶解胡敏酸和富里酸对有机污染物光降解的诱导作用。（4）水体pH可通过改变污染物形态和活性物种反应贡献两种途径改变秸秆源DOM对有机污染物光降解的调控作用，但这一调控作用与有机污染物种类相关；水体离子强度对秸秆源DOM调控有机污染物光降解具有增强作用，而水体溶解氧则是削弱这一调控作用。本项目研究成果有利于加深人们对秸秆源DOM环境光化学效应的认识，为秸秆还田、农业绿色发展提供生态环境保护支撑，并为农田水环境中有机污染物的光化学行为认识与归趋预测提供一定的科学依据。