School of Earth Sciences and Environmental Sciences Graduate Program, The Ohio State University, 125 S. Oval Mall, Columbus Ohio 43210, USA.
Environ Sci Technol. 2009 Nov 15;43(22):8587-92. doi: 10.1021/es9020537.
Sulfadimethoxine (SDM) is an antibiotic often used in combination with ormetoprim to prevent the spread of disease in freshwater aquaculture. It is known to undergo photochemical degradation in natural sunlit surface waters, but the role of dissolved organic matter (DOM) in this process is poorly understood. Our results show that water from a eutrophic catfish pond at the Mississippi State University Delta Research and Extension Center facility in Stoneville, MS facilitates the rapid phototransformation of SDM. In contrast, water from a nearby stream (Deer Creek) whose DOM is derived from allochthonous precursors does not enhance SDM photodegradation. We attribute these disparate results to DOM composition, whereby dissolved organic matter originating from highly eutrophic water bodies is a better SDM photosensitizer. Experiments conducted concurrently using respective autochthonous (Pony Lake, Antarctica) and allochthonous (Suwannee River) derived fulvic acids corroborate these findings. Scavenging experiments and experiments conducted anoxically show that the main indirect photodegradation pathway occurs by triplet excited-state DOM oxidation. Finally, transformation products assayed by mass spectrometry reveal the same major SDM photoproducts in the presence and absence of dissolved organic matter.
磺胺二甲氧嘧啶（SDM）是一种常用于预防淡水水产养殖疾病传播的抗生素，常与奥莫西林联合使用。已知它会在自然阳光照射的地表水中发生光化学降解，但该过程中溶解有机物（DOM）的作用还了解甚少。我们的研究结果表明，来自密西西比州立大学三角洲研究与推广中心在密西西比州斯通维尔的鲶鱼养殖场的水促进了 SDM 的快速光转化。相比之下，来自附近溪流（鹿溪）的水（其 DOM 来源于异源前体）并没有增强 SDM 的光降解。我们将这些不同的结果归因于 DOM 的组成，即来自高度富营养化水体的溶解有机物是更好的 SDM 光敏化剂。同时进行的使用各自的自生（南极洲的庞尼湖）和异源（苏万尼河）衍生的富里酸的实验证实了这些发现。清除实验和缺氧实验表明，主要的间接光降解途径是通过三重态激发态 DOM 氧化发生的。最后，通过质谱分析检测到的转化产物表明，在存在和不存在溶解有机物的情况下，会产生相同的主要 SDM 光产物。
