Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer 1007, 8380000, Santiago, Chile.
Environ Sci Pollut Res Int. 2017 Sep;24(26):20908-20921. doi: 10.1007/s11356-017-9652-7. Epub 2017 Jul 18.
Cyclodextrins (CDs) can improve the apparent solubility and bioavailability of a variety of organic compounds through the formation of inclusion complexes; accordingly, they are suitable for application in innovative remediation technologies of contaminated soils. However, the different interactions in the tertiary system CD/contaminant/soil matrix can affect the bioavailability of the inclusion complex through the possible sorption of CD and CD complex in the soil matrix, as well as with the potential of the sorbed CD to form the complex, concurrent with the desorption processes. This work focuses in changes produced by three different CDs in soil sorption-desorption processes of chlorpyrifos (CPF), diazinon (DZN), and chlorothalonil (CTL), and their major degradation products, 3,5,6-trichloro-2-pyridinol (TCP), 2-isopropyl-6-methyl-4-pyrimidinol, and hydroxy-chlorothalonil (OH-CTL). Cyclodextrins used were β-cyclodextrin (β-CD), methyl-β-cyclodextrin (Mβ-CD), and 2-hydroxypropyl-β-cyclodextrin (HPβ-CD). The studied soils belong to the orders Andisol, Ultisol, and Mollisol with different organic matter contents, mineral composition, and pH. The apparent sorption constants were significantly lower for the three pesticides in the presence of all CDs. The highest displacement of sorption equilibria was produced by the influence of Mβ-CD, with the most pronounced effect for CPF, a pesticide strongly sorbed on soils. The same was obtained for TCP and OH-CTL, highlighting the need to assess the risk of generating higher levels of groundwater contamination with polar metabolites if degradation rates are not controlled. The highest desorption efficiency was obtained for the systems CPF-β-CD, DZN-Mβ-CD, and CTL-Mβ-CD. Since the degree of adsorption of the complex is relevant to obtain an increase in the bioavailability of the contaminant, a distribution coefficient for the complexed pesticide in all CD-soil-pesticide system was estimated by using the apparent sorption coefficients, the stability constant for each CD-pesticide complex, and the distribution coefficients of free pesticide.
环糊精（CDs）可以通过形成包合物来提高各种有机化合物的表观溶解度和生物利用度；因此，它们适合应用于污染土壤的创新修复技术中。然而，三元体系 CD/污染物/土壤基质中的不同相互作用可能会通过 CD 和 CD 复合物在土壤基质中的可能吸附以及吸附的 CD 形成复合物的潜力，同时伴随着解吸过程，影响包合物的生物利用度。本工作重点研究了三种不同的 CDs 在土壤中对毒死蜱（CPF）、二嗪农（DZN）和百菌清（CTL）及其主要降解产物 3,5,6-三氯-2-吡啶醇（TCP）、2-异丙基-6-甲基-4-嘧啶醇和羟基百菌清（OH-CTL）的吸附-解吸过程中的变化。所使用的环糊精为β-环糊精（β-CD）、甲基-β-环糊精（Mβ-CD）和 2-羟丙基-β-环糊精（HPβ-CD）。研究土壤属于安山岩、腐殖质土和黑钙土，具有不同的有机质含量、矿物组成和 pH 值。在所有 CDs 的存在下，三种农药的表观吸附常数明显降低。Mβ-CD 的影响产生了最高的吸附平衡位移，对 CPF 的影响最为显著，CPF 是一种强烈吸附在土壤上的农药。对于 TCP 和 OH-CTL 也是如此，这突出表明，如果不控制降解速率，需要评估生成更高水平的地下水极性代谢物污染的风险。CPF-β-CD、DZN-Mβ-CD 和 CTL-Mβ-CD 系统的解吸效率最高。由于复合物的吸附程度与获得污染物生物利用度的提高有关，因此通过使用表观吸附系数、每个 CD-农药复合物的稳定常数以及自由农药的分配系数，估算了所有 CD-土壤-农药系统中复合物农药的分配系数。
