Department of Environmental Health Sciences, School of Public Health, Seoul National University, Seoul, 08826, South Korea.
Department of Environmental Health Sciences, School of Public Health, Seoul National University, Seoul, 08826, South Korea.
Chemosphere. 2022 Sep;302:134876. doi: 10.1016/j.chemosphere.2022.134876. Epub 2022 May 10.
Propiconazole (PRO) is a triazole fungicide that is frequently detected in the water. In this study, we investigated the kinetics and degradation mechanism of PRO during the UV photolysis and UV/HO processes. PRO was removed by the pseudo-first-order kinetics in both processes. The removal of PRO was enhanced by increasing HO concentration in the UV/HO process. The highest removal under neutral conditions, and lower removal of PRO were observed in acidic and alkaline pHs in the UV/HO process. The presence of natural water ingredients such as Cl, NO, humic acid acted as radical scavengers, but HCO ion acted as both radical promoter and scavenger in the UV/HO process. The transformation products (TPs) of PRO during both processes were identified using LC-QTOF/MS. Four TPs ([M+H] = 238, 256, 306, and 324) were identified during UV photolysis, and six TPs ([M+H] = 238, 256, 306, 324, 356, and 358) were identified in the UV/HO process. Among the identified TPs, TP with [M+H] values of 356 and 358 were newly identified in the UV/HO process. In addition, ionic byproducts, such as Cl, NO, formate (HCOO), and acetate (CHCOO), were newly identified, indicating that significant mineralization was achieved in the UV/HO process. Based on the identified TPs and ionic byproducts, the degradation mechanisms of PRO during two processes were proposed. The major reactions in both processes were ring cleavage and cyclization, and hydroxylation by OH radicals. The Microtox test with Vibrio fischeri showed that, while the toxicity of the reaction solution increased first, then gradually decreased during UV photolysis, the UV/HO process initially increased toxicity at 10 min due to the production of TPs, but toxicity was completely removed as the reaction progressed. The results obtained in this study imply that the UV/HO process is an effective treatment for eliminating PRO, its TPs, and the resulting toxicity in water.
丙环唑（PRO）是一种三唑类杀菌剂，经常在水中被检测到。在这项研究中，我们研究了 PRO 在 UV 光解和 UV/HO 过程中的动力学和降解机制。在这两个过程中，PRO 的去除均遵循准一级动力学。在 UV/HO 过程中，增加 HO 浓度可以提高 PRO 的去除率。在中性条件下，PRO 的去除率最高，而在酸性和碱性 pH 值下，PRO 的去除率较低。在 UV/HO 过程中，天然水成分如 Cl、NO 和腐殖酸作为自由基清除剂，而 HCO 离子则作为自由基促进剂和清除剂。使用 LC-QTOF/MS 鉴定了 PRO 在这两个过程中的转化产物（TPs）。在 UV 光解过程中鉴定出 4 种 TPs([M+H]=238、256、306 和 324)，在 UV/HO 过程中鉴定出 6 种 TPs([M+H]=238、256、306、324、356 和 358)。在所鉴定的 TPs 中，TP 具有 [M+H] 值为 356 和 358 的在 UV/HO 过程中是新鉴定的。此外，还新鉴定了离子副产物，如 Cl、NO、甲酸盐（HCOO）和乙酸盐（CHCOO），这表明在 UV/HO 过程中实现了显著的矿化。根据鉴定的 TPs 和离子副产物，提出了 PRO 在两个过程中的降解机制。两个过程中的主要反应是环断裂和环化，以及 OH 自由基的羟化。采用发光细菌 Vibrio fischeri 的 Microtox 测试表明，在 UV 光解过程中，反应溶液的毒性先增加，然后逐渐降低，而在 UV/HO 过程中，由于 TPs 的产生，毒性在 10 分钟内最初增加，但随着反应的进行，毒性完全消除。本研究结果表明，UV/HO 工艺是一种有效去除水中 PRO、其 TPs 和由此产生的毒性的处理方法。
