化学
溶解有机碳
光降解
光化学
腐植酸
羟基化
光解
单线态氧
光敏剂
羟基自由基
环境化学
有机化学
激进的
氧气
光催化
催化作用
肥料
酶
作者
Lei Zhou,Yuefei Ji,Chao Zeng,Ya Zhang,Zunyao Wang,Xi Yang
出处
期刊:Water Research
[Elsevier]
日期:2012-10-04
卷期号:47 (1): 153-162
被引量:98
标识
DOI:10.1016/j.watres.2012.09.045
摘要
Dissolved organic matter (DOM) is an important photosensitizer for the phototransformation of organic contaminants in sunlit natural waters. This article focuses on the photolysis kinetics and mechanism of sunscreen agent p-aminobenzoic acid (PABA) in the presence of four kinds of DOM; Suwannee River fulvic acid (SRFA), Suwannee River humic acid (SRHA), Nordic Lake fulvic acid (NOFA) and Nordic Lake humic acid (NOHA). It is evident that direct photolysis of PABA is highly pH-dependent because different species of PABA have different electrical densities on the ring system. The presence of four kinds of DOM inhibits the photolysis of PABA primarily due to their light screening effect. Meanwhile, a complex interaction involving energy transfer, triplet carbonyl group induced electron transfer, and amino acid induced proton abstraction between PABA and DOM is verified by competition kinetics experiments and density functional theory (DFT) computation. In addition, DOM-induced singlet oxygen (1O2) and hydroxyl radical (OH) are determined to play an insignificant role in PABA photolysis by competition dynamics method. Photoproducts identification using solid phase extraction–liquid chromatography–mass spectrometry (SPE–LC–MS) techniques reveals that the distribution of the photoproducts could not be affected by the addition of DOM. Two photodegradation pathways of PABA are temporarily proposed, in which the di(tri)-polymerization of intermediates are the dominant pathway whereas the oxidation of amino group to nitryl followed by hydroxylation is a minor process. Our findings reveal that direct photolysis is the dominant transformation pathway of PABA in natural sunlit waters, while the presence of DOM could evidently influence such process by light screening effect, energy transfer, electron transfer and proton abstraction mechanism. The findings in this study provide useful information for understanding of interaction between DOM and organic contaminants.
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