Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, United States.
Department of Horticulture, Oregon State University, Corvallis, OR, United States.
Sci Total Environ. 2015 Dec 15;538:683-91. doi: 10.1016/j.scitotenv.2015.08.035. Epub 2015 Aug 29.
Encapsulation of pesticide active ingredients in polymers has been widely employed to control the release of poorly water-soluble active ingredients. Given the high dispersibility of these encapsulated pesticides in water, they are expected to behave differently compared to their active ingredients; however, our current understanding of the fate and effects of encapsulated pesticides is still limited. In this study, we employed a central composite design (CCD) to investigate how pH and ionic strength (IS) affect the hydrodynamic diameter (HDD) and zeta potential of encapsulated λ-cyhalothrin and how those changes affect the exposure and toxicity to Daphnia magna. R(2) values greater than 0.82 and 0.84 for HDD and zeta potential, respectively, irrespective of incubation time suggest those changes could be predicted as a function of pH and IS. For HDD, the linear factor of pH and quadratic factor of pH×pH were found to be the most significant factors affecting the change of HDD at the beginning of incubation, whereas the effects of IS and IS×IS became significant as incubation time increased. For zeta potential, the linear factor of IS and quadratic factor of IS×IS were found to be the most dominant factors affecting the change of zeta potential of encapsulated λ-cyhalothrin, irrespective of incubation time. The toxicity tests with D. magna under exposure conditions in which HDD or zeta potential of encapsulated λ-cyhalothrin was maximized or minimized in the overlying water also clearly showed the worst-case exposure condition to D. magna was when the encapsulated λ-cyhalothrin is either stable or small in the overlying water. Our results show that water quality could modify the fate and toxicity of encapsulated λ-cyhalothrin in aquatic environments, suggesting understanding their aquatic interactions are critical in environmental risk assessment. Herein, we discuss the implications of our findings for risk assessment.
将农药活性成分封装在聚合物中已被广泛用于控制水溶性差的活性成分的释放。鉴于这些封装农药在水中的高分散性，它们的行为预计与它们的活性成分不同；然而，我们目前对封装农药的归宿和影响的理解仍然有限。在这项研究中，我们采用中心复合设计 (CCD) 来研究 pH 值和离子强度 (IS) 如何影响封装的 λ-氯氟氰菊酯的水动力直径 (HDD) 和 ζ 电位，以及这些变化如何影响对大型溞的暴露和毒性。HDD 和 ζ 电位的 R² 值分别大于 0.82 和 0.84，无论孵育时间如何，这表明可以根据 pH 值和 IS 值预测这些变化。对于 HDD，在孵育开始时，pH 值的线性因子和 pH×pH 的二次因子被发现是影响 HDD 变化的最显著因素，而随着孵育时间的增加，IS 和 IS×IS 的影响变得显著。对于 ζ 电位，IS 的线性因子和 IS×IS 的二次因子被发现是影响封装的 λ-氯氟氰菊酯 ζ 电位变化的最主要因素，无论孵育时间如何。在暴露条件下对大型溞进行的毒性测试中，封装的 λ-氯氟氰菊酯的 HDD 或 ζ 电位在表层水中最大或最小时，也明显表明对大型溞的最坏暴露条件是当封装的 λ-氯氟氰菊酯在表层水中稳定或较小。我们的结果表明，水质可以改变封装的 λ-氯氟氰菊酯在水生环境中的归宿和毒性，这表明了解它们在水生环境中的相互作用对于环境风险评估至关重要。在此，我们讨论了我们的研究结果对风险评估的意义。
