Monkiedje Adolphe, Spiteller Michael
Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, Cameroon.
Chemosphere. 2002 Nov;49(6):659-68. doi: 10.1016/s0045-6535(02)00325-9.
Laboratory soil sorption experiments were conducted on mefenoxam, formulated metalaxyl (F-metalaxyl), pure metalaxyl (P-metalaxyl) and metalaxyl acid metabolite to elucidate differences in their sorptive behaviour on typical Cameroonian forest soil (sand clay loam, pH 4.8 and 3.01% OC) and German soil (sandy loam, pH 7.2, 1.69% OC) using a batch equilibrium method. The data obtained on all test chemicals conformed to linear and Freundlich adsorption isotherms. The Langmuir equation failed to describe the sorption of the substances tested. All substances were adsorbed to a greater extent by the Cameroonian soil. The average percentage adsorptions for mefenoxam, F-metalaxyl, P-metalaxyl and the acid metabolite on the Cameroonian soil were 27.8%, 28.3%, 31.8% and 46.8% respectively while for the German soil they were 21.7%, 21.5%, 24.7% and 9.8% respectively. The KD and KF parameters and the Freundlich exponential term (1/n) were low, indicating that the interactions between soil particles and the fungicides were weak. The sorption parameters were lower in the German soil. P-metalaxyl exhibited a higher adsorption capacity than F-metalaxyl in both soils. Mefenoxam and F-metalaxyl exhibited similar sorption parameters in soils, whereas those of P-metalaxyl and acid metabolite differed. Differences observed in the adsorption between the two soils could be attributed to their properties. Desorption studies revealed that the adsorbed fungicides were not firmly retained by soil particles and their adsorption was reversible. Desorption of adsorbed mefenoxam, P-metalaxyl and of the acid metabolite from German soil was almost completely reversible with percentage desorption rates of more than 91.0%, whereas the rate for F-metalaxyl was 74.1%. All compounds exhibited some resistance to desorption from the Cameroonian soil, with percentage desorption rates less than 77.0%. Therefore if degradation in the soil is slow the fungicides described have a potential to leach to lower soil horizons.
在甲霜灵、精甲霜灵（F-甲霜灵）、甲霜灵原药（P-甲霜灵）和甲霜灵酸代谢物上进行了实验室土壤吸附实验，以使用批次平衡法阐明它们在典型喀麦隆森林土壤（砂质粘壤土，pH 4.8，有机碳含量3.01%）和德国土壤（砂壤土，pH 7.2，有机碳含量1.69%）上吸附行为的差异。所有受试化学品获得的数据均符合线性和Freundlich吸附等温线。Langmuir方程未能描述受试物质的吸附情况。喀麦隆土壤对所有物质的吸附程度更高。喀麦隆土壤中甲霜灵、F-甲霜灵、P-甲霜灵和酸代谢物的平均吸附百分比分别为27.8%、28.3%、31.8%和46.8%，而德国土壤中分别为21.7%、21.5%、24.7%和9.8%。分配系数（KD）和Freundlich参数（KF）以及Freundlich指数项（1/n）较低，表明土壤颗粒与杀菌剂之间的相互作用较弱。德国土壤中的吸附参数较低。在两种土壤中，P-甲霜灵的吸附能力均高于F-甲霜灵。甲霜灵和F-甲霜灵在土壤中的吸附参数相似，而P-甲霜灵和酸代谢物的吸附参数不同。两种土壤之间吸附的差异可能归因于它们的性质。解吸研究表明，被吸附的杀菌剂未被土壤颗粒牢固保留，其吸附是可逆的。德国土壤中被吸附的甲霜灵、P-甲霜灵和酸代谢物的解吸几乎完全可逆，解吸率超过91.0%，而F-甲霜灵的解吸率为74.1%。所有化合物从喀麦隆土壤中的解吸都表现出一定抗性，解吸率低于77.0%。因此，如果土壤中的降解缓慢，所述杀菌剂有可能淋溶到土壤下层。
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