溶解有机物对莱州湾磺胺类抗生素间接光降解的影响机制

The residues of sulfonamides (SAs) in the coastal waters would constitute a threat to human health. Indirect photodegradation is an important transformation pathway of SAs in surface seawaters, and the composition of dissolved organic matter (DOM) is the critical factor that affects the indirect photodegradation. But so far, the influence mechanism of DOM compositions on the indirect photodegradation of SAs is still unknown. This project will select Laizhou Bay as the research area, and analyze the effects of reactive intermediates generated by DOM on the indirect photodegradation of SAs by electron spin resonance, molecular probe and free radical quenching experiment. Classifying and identifying the compositions of DOM by resin separation, cross flow ultrafiltration, UV-visible absorption spectrum, excitation–emission matrix spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC) and fourier transform ion cyclotron resonance mass spectrometry will help us in the comprehension of the main compositions and molecular structure of DOM that participate in the indirect photodegradation of SAs and the influence mechanism. The effects of salinity, pH, nitrate and bicarbonate on the indirect photodegradation of SAs in DOM solutions will be investigated to better understand the photodegradation kinetics and degradation mechanisms of SAs in the surface waters of Laizhou Bay. The project will provide theoretical basis for accurately grasping the fate of SAs in the coastal areas and assessing its ecological risks.

近岸海域中磺胺类抗生素（SAs）的残留会对人类健康产生威胁。间接光降解是表层海水中SAs的重要转化途径，溶解有机物（DOM）的结构组成是影响其间接光降解能力的关键因素，而目前对于DOM结构组成对SAs间接光降解影响机制的认识尚不明确。本项目选取莱州湾为研究区域，采用电子自旋共振、分子探针和自由基猝灭等技术分析DOM产生的活性中间体对SAs间接光降解的作用；采用树脂分离、切向超滤、紫外可见吸收光谱、三维荧光光谱-平行因子分析法与傅里叶变换离子回旋共振质谱等技术对DOM进行分类识别，揭示DOM中参与SAs间接光降解的主要组分及分子结构，阐明DOM的结构组成对SAs间接光降解的影响机制；研究DOM溶液中盐度、pH值、硝酸根和碳酸氢根对SAs间接光降解的影响，揭示SAs在莱州湾表层水体中光降解过程的反应动力学及降解机理，为准确掌握近岸海域环境中SAs的归趋和评估其生态风险提供理论依据。

近岸海域中磺胺类抗生素（SAs）的残留会对人类健康产生威胁。间接光降解是表层海水中SAs的重要转化途径，而目前对于溶解有机物（DOM） 结构组成对SAs间接光降解影响机制的认识尚不明确。因此本文利用自由基猝灭实验研究了DOM产生的活性中间体对磺胺甲基嘧啶（SM）和磺胺噻唑（ST）间接光降解的影响，利用切向超滤和树脂分离技术分别对DOM进行分离，并利用三维荧光光谱-平行因子分析法（EEMs-PARAFAC）以及紫外-可见光谱进行表征，分析了DOM溶液中盐度、pH值、硝酸根和碳酸氢根对SAs间接光降解的影响，揭示SAs在莱州湾表层水体中光降解过程的反应动力学及降解机理，为准确掌握莱州湾SAs的归趋和评估其生态风险提供理论依据。得到的主要结果如下：.（1）DOM可通过产生活性中间体促进SAs的间接光降解，活性中间体对SAs间接光降解的贡献不同，3DOM*和1O2分别在SM和ST的间接光降解过程中起主要作用。.（2）不同DOM对SAs间接光降解的影响与DOM的结构组成有关，陆源类腐殖质组分对SAs间接光降解的影响要显著强于海源类腐殖质组分。超滤组分中＞10 kDa对SAs间接光降解促进作用较低。＜3 kDa组分、3-5 kDa组分中含有的陆源类腐殖质组分较多，能产生更多的活性中间体，对SAs间接光降解具有较显著的促进作用。亲水酸性组分(HIA)、疏水酸性组分(HOA)以及疏水碱性组分(HOB)对SAs间接光降解速率促进作用较大。.（3）pH可通过改变活性中间体的稳态浓度和SAs的形态影响SAs的间接光降解，碱性环境更有利于活性中间体的生成。盐度、硝酸根和碳酸氢根均可通过改变活性中间体的稳态浓度影响抗生素的间接光降解。.（4）莱州湾海水DOM以大分子量和亲水性结构为主，陆源类腐殖质组分是莱州湾海水DOM生成活性中间体的主要组分，是促进SAs间接光降解的关键组分。