Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 3250 Fitts-Woolard Hall, 915 Partners Way, Raleigh NC 27695, USA.
Geosyntec Consultants Inc., 2501 Blue Ridge Road, Suite 430, Raleigh, NC, 27607, USA.
Environ Sci Process Impacts. 2022 May 25;24(5):805-824. doi: 10.1039/d1em00545f.
Wastewater treatment wetlands are aquatic systems where diverse dissolved organic matter (DOM) compositions physically interact. Complex photochemical behaviors ensue, leading to uncertainties in the prediction of indirect photodegradation rates for organic contaminants. Here, we evaluate the photosensitization ability of whole water DOM samples from a treatment wetland and wastewater treatment plant (WWTP) in North Carolina to photodegrade target pharmaceuticals. Optical characterization using ultraviolet-visible and excitation-emission matrix spectroscopy shows that wetland DOM has higher aromaticity than WWTP DOM and that WWTP secondary treatment processes increase aromaticity, overall molecular weight, and humic character of wastewater DOM. Our application of a reversed-phase HPLC method to assess DOM polarity distinctly reveals that a subset of the wetland samples possesses an abundance of hydrophobic DOM moieties. Hydroxyl radicals (˙OH) mediate the majority (>50%) of the indirect photodegradation for amoxicillin (AMX), atenolol (ATL), and 17α-ethinylestradiol (EE2), while singlet oxygen (O) is presumed to be solely responsible for the photodegradation of cimetidine (CME). Our findings suggest that hydrophobic interactions and improved accessibility to photogenerated reactive intermediates lead to significant increases in photosensitization efficiencies and overall indirect photodegradation rates of AMX, ATL, and EE2 for the hydrophobic wetland samples. In contrast, CME photosensitization yields are unaffected by polarity and trend positively with optical indicators of sunlight-induced DOM photobleaching and humification, suggesting that wetland processing favors faster O photogeneration. These relationships highlight the uncertainties in photosensitization yields and effects of DOM optical properties and polarity on the photochemical fate of organic contaminants.
污水处理湿地是各种溶解有机物质（DOM）物理相互作用的水生系统。复杂的光化学反应随之发生，导致对有机污染物间接光降解速率的预测存在不确定性。在这里，我们评估了来自北卡罗来纳州处理湿地和废水处理厂（WWTP）的全水 DOM 样品对目标药物进行光降解的光敏能力。使用紫外可见和激发发射矩阵光谱学进行光学特征描述表明，湿地 DOM 的芳香度高于 WWTP DOM，WWTP 二级处理过程增加了废水 DOM 的芳香度、总分子量和腐殖质特征。我们应用反相高效液相色谱法评估 DOM 极性的方法明显表明，湿地样品中的一部分具有丰富的疏水性 DOM 部分。˙OH 介导了阿莫西林（AMX）、阿替洛尔（ATL）和 17α-乙炔基雌二醇（EE2）的大部分（>50%）间接光降解，而单线态氧（O）被认为是西咪替丁（CME）光降解的唯一原因。我们的发现表明，疏水性相互作用和对光生反应中间体的更好接触导致 AMX、ATL 和 EE2 的间接光降解速率和整体光敏效率显著增加，这对疏水性湿地样品而言是如此。相比之下，CME 的光敏产率不受极性影响，并且与阳光诱导 DOM 光漂白和腐殖化的光学指标呈正相关，这表明湿地处理有利于更快地产生 O。这些关系突出了 DOM 光学性质和极性对有机污染物光化学命运的光敏产率和影响的不确定性。
