Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, CH-8092 Zürich, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, CH-8092 Zürich, Switzerland; School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Water Res. 2014 Jun 15;57:183-92. doi: 10.1016/j.watres.2014.03.019. Epub 2014 Mar 20.
Sulfadiazine (SD) and sulfamethoxazole (SMX) are widely used sulfonamide antibiotics, which are present as contaminants in surface waters and are known to undergo phototransformation. This kinetic study was conducted to identify the processes responsible for their phototransformation in sunlit surface waters. Water samples from the Thur River (Switzerland) and from a pilot wastewater treatment plant, as well as aqueous solutions of two well-characterized natural dissolved organic matter (DOM) extracts, namely Suwannee River and Pony Lake fulvic acids (SRFA, PLFA), were examined. Both sulfonamides were found to undergo direct and indirect phototransformation, with contributions of excited triplet states of DOM and of effluent organic matter (EfOM) and possibly of hydroxyl radical and other unidentified reactive species. Under simulated sunlight, SMX mainly reacted through direct phototransformation, with a certain contribution of indirect phototransformation occurring for a wastewater effluent. The behavior of SD was found to be more diverse. For river waters, wastewater effluents and PLFA solutions, indirect phototransformation was predominant, while for SRFA solutions direct phototransformation prevailed. The rates of phototransformation of SD were interpreted as the result of a complex interplay between the photosensitizing and the inhibitory effect of DOM/EfOM, with an additional component related to the nitrite ion as a source of photoproduced hydroxyl radical. For typical conditions found in surface waters comparable to the Thur River, phototransformation half-lives on the order of 3-13 d were estimated for the two studied sulfonamides.
磺胺嘧啶（SD）和磺胺甲恶唑（SMX）是广泛使用的磺胺类抗生素，它们作为污染物存在于地表水，已知会发生光转化。本动力学研究旨在确定导致它们在阳光照射的地表水中光转化的过程。研究了来自图尔河（瑞士）和一个试点废水处理厂的水样，以及两种经过充分表征的天然溶解有机物质（DOM）提取物，即苏万尼河和小马湖富里酸（SRFA、PLFA）的水溶液。结果发现，这两种磺胺类药物都经历了直接和间接的光转化，DOM 和废水有机物（EfOM）的激发三重态以及可能的羟基自由基和其他未识别的反应性物质都有贡献。在模拟阳光下，SMX 主要通过直接光转化反应，而对于废水，间接光转化也有一定的贡献。SD 的行为被发现更为多样化。对于河水、废水和 PLFA 溶液，间接光转化占主导地位，而对于 SRFA 溶液，直接光转化占主导地位。SD 的光转化速率被解释为 DOM/EfOM 的光敏和抑制作用之间复杂相互作用的结果，其中还涉及到亚硝酸盐离子作为光产生的羟基自由基的来源的附加成分。对于类似于图尔河的地表水中发现的典型条件，估计了两种研究磺胺类药物的光转化半衰期约为 3-13 天。
