Department Applied Geology, Geoscience Centre of University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany.
Water Res. 2012 May 1;46(7):2131-9. doi: 10.1016/j.watres.2012.01.028. Epub 2012 Jan 31.
The antibiotic sulfonamide drug sulfamethoxazole (SMX) is extensively used in both human and veterinary medicine. Since it cannot be completely eliminated by the typical state-of-the-art wastewater treatment technology, it is frequently detected in the water cycle. SMX, as aromatic amine, can undergo abiotic transformations with the under denitrifying conditions produced nitrogen species nitric oxide (NO) and nitrite (NO(2)(-)). NO and aromatic amines are commonly known to form diazonium cations. Depending on the reaction conditions the diazonium cation disintegrates under cleavage of elementary nitrogen and substitutes its diazo-group by an NO(2)-group or by hydrogen. Following this approach, two transformation products (TPs) of the persistent SMX under denitrifying conditions were hypothesized and synthesized: 4-nitro-N-(5-methylisoxazol-3-yl)-benzenesulfonamide (4-nitro-SMX) and N-(5-methylisoxazol-3-yl)-benzenesulfonamide (desamino-SMX). The synthesized compounds were identified by Nuclear Magnetic Resonance (NMR) spectroscopy and used as reference standards for their confirmation and quantification in denitrifying water/sediment batch experiments and in environmental samples. During the denitrifying degradation experiment SMX was no longer detected after 10 days whereas increasing concentrations of the two TPs were observed. However, at day 87 the SMX concentration recovered to 53 ± 16% of the initial concentration after most of the nitrate was consumed. A retransformation of 4-nitro-SMX to SMX was postulated and confirmed by another anoxic water/sediment test in the absence of nitrate as electron acceptor. Both TPs were also detected in karst spring samples, highlighting the need and benefit of focusing on transformation products in environmental studies. Furthermore, the consideration of the retransformation potential of 4-nitro-SMX can substantially improve the understanding of SMX behavior during processes such as bank filtration and artificial recharge.
抗生素磺胺类药物磺胺甲恶唑（SMX）广泛应用于人类和兽医医学。由于它不能被典型的最先进的废水处理技术完全去除，因此它经常在水循环中被检测到。SMX 作为芳香胺，可在产生氮物种一氧化氮（NO）和亚硝酸盐（NO(2)(-))的缺氧条件下进行非生物转化。众所周知，NO 和芳香胺通常会形成重氮阳离子。根据反应条件，重氮阳离子在裂解时会分解，其中初级氮被取代，其重氮基团被 NO(2)-基团或氢取代。基于此方法，在缺氧条件下假设并合成了持久的 SMX 的两种转化产物（TP）：4-硝基-N-（5-甲基异恶唑-3-基）-苯磺酰胺（4-硝基-SMX）和 N-（5-甲基异恶唑-3-基）-苯磺酰胺（去氨基-SMX）。通过核磁共振（NMR）光谱鉴定合成的化合物，并将其用作在缺氧水/沉积物批量实验和环境样品中鉴定和定量的参考标准。在缺氧降解实验中，SMX 在 10 天后不再被检测到，而两种 TP 的浓度则增加。然而，在第 87 天，当大部分硝酸盐被消耗后，SMX 浓度恢复到初始浓度的 53±16%。在没有硝酸盐作为电子受体的另一个缺氧水/沉积物测试中，推测并证实了 4-硝基-SMX 向 SMX 的再转化。两种 TP 也在岩溶泉样本中被检测到，这突出了在环境研究中关注转化产物的必要性和益处。此外，考虑到 4-硝基-SMX 的再转化潜力可以大大提高对 SMX 在诸如河岸过滤和人工补给等过程中的行为的理解。
