Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer 1007, 8380000, Santiago, Chile.
Environ Sci Pollut Res Int. 2018 Sep;25(25):25020-25035. doi: 10.1007/s11356-018-2559-0. Epub 2018 Jun 22.
The intensive use of insecticides such as chlorpyrifos (CPF) and diazinon (DZN) in the agricultural activities worldwide has produced contamination of soils and/or transport to non-target areas including their distribution to surface and groundwaters. Cyclodextrins (CDs) have been proposed as an alternative in remediation technologies based on the separation of contaminants from soils because they could allow a higher bioavailability for their degradation with a low environmental impact. In this work, the degradation pattern of CPF and DZN and the formation and dissipation of the major degradation products 3,5,6-trichloro-2-pyridinol (TCP) and 2-isopropyl-6-methyl-4-pyrimidinol (IMPH) was established in four agricultural volcanic and non-volcanic soils belonging to Andisol, Ultisol, and Mollisol orders. Both pesticides were highly adsorbed in these soils, consequently, with a greater probability of contaminating them. In contrast, the adsorption of their two main metabolites was low or null; therefore, they are potential groundwater contaminants. The degradation processes were studied in the natural and amended soils with β-cyclodextrin (β-CD) and methyl-β-cyclodextrin (Mβ-CD) for CPF and DZN, respectively. A slow degradation of CPF and DZN was obtained for volcanic soils with observable residues until the end of the incubation time (150-180 days). In Mollisols, the higher degradation rate of CPF was favored by the neutral to basic pH, and for DZN it was related to the lower adsorption and higher bioavailability. The amendment of soils with CDs produced slower degradation rates which led to a greater concentration of the compounds at the end of the incubation time. This effect was more pronounced for DZN. The exception was the Andisol, with no significant changes for both compounds regarding the unamended soil. No residues of TCP were observed for this soil in both conditions during the whole incubation time; nevertheless, the accumulation of TCP was significant in the Ultisol and Mollisols, but the concentrations were lower for the amended soils. The accumulation of IMPH was important in Mollisol amended soils; however, their residues were observed in the volcanic soils during the whole incubation period in the natural and amended soils. An important enhancement of the microbial activity occurred in the system β-CD/CPF in Mollisols, without a more effective degradation of the insecticide. The opposite effect was observed in the system Mβ-CD/DZN mainly in the oxidative activity in all soils. The higher degradation of DZN and IMPH in natural Mollisols was related to the higher hydrolytic and oxidative activities. The stability of the inclusion complexes formed could play an important role for explaining the results obtained with the amendments.
全世界农业活动中大量使用氯蜱（CPF）和二嗪农（DZN）等杀虫剂，导致土壤受到污染和/或污染物转移到非目标区域，包括其分布到地表水和地下水。环糊精（CDs）因其可用于从土壤中分离污染物而被提议作为修复技术的替代物，因为它们可以提高其降解的生物利用度，同时对环境的影响较小。在这项工作中，建立了 CPF 和 DZN 的降解模式，以及主要降解产物 3,5,6-三氯-2-吡啶醇（TCP）和 2-异丙基-6-甲基-4-嘧啶醇（IMPH）的形成和消散，在属于安第斯土、砖红壤和淋溶土的四个农业火山和非火山土壤中进行。这两种农药在这些土壤中高度吸附，因此，污染这些土壤的可能性更大。相比之下，它们两种主要代谢物的吸附量较低或为零；因此，它们是潜在的地下水污染物。在天然土壤和添加了β-环糊精（β-CD）和甲基-β-环糊精（Mβ-CD）的土壤中，分别研究了 CPF 和 DZN 的降解过程。在火山土壤中，CPF 和 DZN 的降解速度较慢，可观察到残留物质，直到培养时间结束（150-180 天）。在蒙脱石中，中性至碱性 pH 有利于 CPF 的更高降解速率，而对于 DZN，它与较低的吸附和更高的生物利用度有关。土壤中添加 CDs 会导致降解速度变慢，从而在培养时间结束时导致化合物浓度更高。对于 DZN，这种效果更为明显。安第斯土是个例外，与未添加 CD 的土壤相比，这两种化合物的含量没有明显变化。在整个培养期间，在这两种情况下，该土壤中均未观察到 TCP 的残留；然而，在砖红壤和蒙脱石中，TCP 的积累量显著，但添加土壤中的浓度较低。IMP 的积累在添加蒙脱石的土壤中很重要；然而，在天然和添加土壤中，整个培养期间都观察到了火山土壤中的残留。在添加 CD 的 Mollisol 系统中，微生物活性显著增强，但对杀虫剂的降解效果并没有更有效。在添加 Mβ-CD 的 DZN 系统中观察到了相反的效果，主要是在所有土壤中的氧化活性。天然蒙脱石中 DZN 和 IMPH 的较高降解与更高的水解和氧化活性有关。形成的包合物的稳定性可能对解释添加物的结果起着重要作用。
