Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: Identification of transformation products and pathways
Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: Identification of transformation products and pathways
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DOI：
10.1016/j.chemosphere.2012.01.016
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发表时间：
2012-05-01
期刊：
影响因子：
8.8
通讯作者：
Fernandez-Alba, Amadeo R.
中科院分区：
文献类型：
--
作者：
Pareja, Lucia;Perez-Parada, Andres;Fernandez-Alba, Amadeo R.
二氯喹啉酸（QNC）是水稻生产中常用的一种有效而持久的除草剂。该除草剂在环境中具有平均持久性，因此认为其残留物具有环境相关性。然而，很少有人研究其环境行为和降解。本文研究了目标化合物在超纯水和稻田水中的直接光解和TiO 2降解。在250和700 W·m（-2）下，QNC在超纯水中光解10 h后，浓度分别下降26%和54%。而在相同的辐照条件下，稻田水中二氯喹啉酸的含量几乎保持不变。QNC在超纯水中降解40 min后完全消失，而在稻田水中降解98%的QNC需要130 min，通过液相色谱-电喷雾-四极杆飞行时间质谱（LC-TOF-MS）和精确质量测定，对QNC的主要转化产物进行了结构表征，提出了QNC可能的光解和光催化降解途径. QNC降解的关键步骤是吡啶环在9位的羟基化，然后开环和/或氧化脱氯。(C)2012爱思唯尔有限公司保留所有权利。
Quinclorac (QNC) is an effective but rather persistent herbicide commonly used in rice production. This herbicide presents a mean persistence in the environment so its residues are considered of environmental relevance. However, few studies have been conducted to investigate its environmental behavior and degradation. In the present work, direct photolysis and TiO2 photocatalysis of the target compound in ultrapure and paddy field water were investigated. After 10 h photolysis in ultrapure water, the concentration of QNC declined 26% and 54% at 250 and 700 W m(-2), respectively. However, the amount of quinclorac in paddy field water remained almost constant under the same irradiation conditions. QNC dissipated completely after 40 min of TiO2 photocatalysis in ultrapure water, whereas 130 min were necessary to degrade 98% of the initial concentration in paddy field water.Possible QNC photolytic and photocatalytic degradation pathways are proposed after structure elucidation of the main transformation products, through liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry and exact mass measurements. Pyridine ring hydroxylation at C-9 followed by ring opening and/or oxidative dechlorination were the key steps of QNC degradation. (C) 2012 Elsevier Ltd. All rights reserved.