Konstantinou I K, Zarkadis A K, Albanis T A
Department of Chemistry, University of Ioannina, Greece.
J Environ Qual. 2001 Jan-Feb;30(1):121-30. doi: 10.2134/jeq2001.301121x.
The photochemical degradation of herbicides belonging to different chemical groups has been investigated in different types of natural waters (ground, river, lake, marine) and distilled water as well as in soils with different texture and composition. Studied herbicides and chemical groups included atrazine, propazine, and prometryne (s-triazines); propachlor and propanil (acetanilides); and molinate (thiocarbamate). The degradation kinetics were monitored under natural conditions of sunlight and temperature. Photodegradation experiments were performed in May through July 1998 at low concentrations in water samples (2-10 mg/L) and soil samples (5-20 mg/kg), which are close to usual field dosage. The photodegradation rates of all studied herbicides in different natural waters followed a pseudo-first order kinetics. The half-lives of the selected herbicides varied from 26 to 73 calendar days in waters and from 12 to 40 d in soil surfaces, showing that the degradation process depends on the constitution of the irradiated media. The presence of humic substances in the lake, river, and marine water samples reduces degradation rates in comparison with the distilled and ground water. On the contrary, the degradation in soil is accelerated as the percentage of organic matter increases. Generally, the photodegradation process in soil is faster than in water. The major photodegradation products identified by using gas chromatography-mass spectrometry (GC-MS) techniques were the hydroxy and dealkylated derivatives for s-triazines, the dechlorinated and hydroxy derivative for the anilides, and the keto-derivative for the thiocarbamate, indicating a similar mode of degradation for each chemical category.
研究人员在不同类型的天然水体（地下水、河水、湖水、海水）、蒸馏水以及不同质地和成分的土壤中，对属于不同化学组的除草剂的光化学降解进行了研究。所研究的除草剂和化学组包括莠去津、扑灭津和扑草净（均三嗪类）；毒草胺和敌稗（乙酰苯胺类）；以及禾草敌（硫代氨基甲酸盐类）。在阳光和温度的自然条件下监测降解动力学。1998年5月至7月，在水样（2-10毫克/升）和土样（5-20毫克/千克）的低浓度下进行光降解实验，这些浓度接近田间常用剂量。所有研究的除草剂在不同天然水体中的光降解速率均遵循准一级动力学。所选除草剂在水中的半衰期为26至73个日历日，在土壤表面为12至40天，这表明降解过程取决于受辐照介质的组成。与蒸馏水和地下水相比，湖泊、河流和海水样品中腐殖质的存在降低了降解速率。相反，土壤中的降解随着有机质百分比的增加而加速。一般来说，土壤中的光降解过程比水中的更快。使用气相色谱-质谱（GC-MS）技术鉴定出的主要光降解产物，对于均三嗪类是羟基和脱烷基衍生物，对于乙酰苯胺类是脱氯和羟基衍生物，对于硫代氨基甲酸盐类是酮衍生物，这表明每个化学类别具有相似的降解模式。
