Xu Gang, Li Fasheng, Wang Qunhui
Department of Environmental Science and Engineering, Harbin Institute of Technology, Harbin, P.R. China.
J Environ Sci Health B. 2007 Feb;42(2):165-71. doi: 10.1080/03601230601123300.
The effects of two humic acids (HAs) of different origins on the photodegradation of the chloroacetanilide herbicides acetochlor, propisochlor and butachlor were investigated in this study. One of the tested HAs was a standard sample that was purchased from a commercial source, and the other was isolated from the black soil of Northeast China. The photolysis of all three herbicides followed pseudo-first-order kinetics under ultraviolet (UV) irradiation conditions, regardless of whether HAs were present or not. Both HAs improved the photolysis rates of acetochlor in a dose-reversed way, whereas they inhibited butachlor degradation under all experimental concentrations. The two HAs differed in their effects on propisochlor photolysis, changing from enhancement to inhibition, depending on the origin and concentration of HAs. Element and Fourier Transform Infrared spectroscopy analyses showed that the isolated HAs had more polysaccharides and less aliphatic groups than the commercial HAs, and it was indicated that some characteristic radicals (C=O, O-H and phenolic hydroxyls) in HAs were involved in the photolysis of the herbicides. Gas chromatography/mass spectrometry (GC/MS) analyses indicated that the presence of HAs had no effects on the photolysis pathway and photoproduct species of the three herbicides.
本研究考察了两种不同来源的腐殖酸（HAs）对氯代乙酰苯胺类除草剂乙草胺、异丙草胺和丁草胺光降解的影响。其中一种受试腐殖酸是从商业渠道购买的标准样品，另一种是从中国东北黑土中分离得到的。在紫外（UV）照射条件下，无论是否存在腐殖酸，三种除草剂的光解均遵循准一级动力学。两种腐殖酸均以剂量反转的方式提高了乙草胺的光解速率，而在所有实验浓度下均抑制了丁草胺的降解。两种腐殖酸对异丙草胺光解的影响不同，根据腐殖酸的来源和浓度，其作用从促进变为抑制。元素分析和傅里叶变换红外光谱分析表明，与商业腐殖酸相比，分离得到的腐殖酸含有更多的多糖和更少的脂肪族基团，并且表明腐殖酸中的一些特征基团（C=O、O-H和酚羟基）参与了除草剂的光解。气相色谱/质谱（GC/MS）分析表明，腐殖酸的存在对三种除草剂的光解途径和光解产物种类没有影响。
