Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 208 Mann Hall, 2501 Stinson Drive, Raleigh, NC 27695-7908, United States.
Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175, United States.
Sci Total Environ. 2019 Jan 15;648:923-934. doi: 10.1016/j.scitotenv.2018.08.138. Epub 2018 Aug 15.
Constructed wetlands have the capacity to degrade a host of contaminants of emerging concern through photodegradation via sunlight produced reactive oxygen species. Dissolved organic matter (DOM) is a critical intermediary in photodegradation as it influences the production of reactive oxygen species. In this study, the photochemical behavior of DOM of wastewater treated in constructed wetlands was characterized. Whole water samples and fractionated DOM were characterized using SUVA, spectral slope ratios, excitation emission matrix fluorescence spectroscopy (EEMs), and proton nuclear magnetic resonance (H NMR). Photoreactivity was assessed by measuring formation rates and steady state concentrations of hydroxyl radical (OH), singlet oxygen (O), and the triplet excited states of DOM (DOM). The effluent was observed to transition from a microbially sourced protein-like DOM to a terrestrial DOM with higher aromaticity. Size exclusion chromatography revealed an 18% increase in larger molecular weight fractions of vegetated wetland effluent DOM. Additionally, wetland effluent DOM was observed to have a 32% increase in the aromatic region of H NMR spectra as compared to untreated wastewater. H NMR analysis also indicated an increase in the complexity of wetland effluent DOM. Fluorescence intensity fraction of the protein-like Peak T (Ex/Em:278/342 nm) of EEMs decreased by 16% from the untreated wastewater to wetland effluent. A negative correlation between the percent fluorescence of Peak T (Ex/Em:278/342 nm) and Peaks A (Ex/Em:245/460 nm), C (Ex/Em:336/435 nm), and M (Ex/Em:312/400 nm) of the excitation emission spectra confirmed the transition from a spectrum of pure wastewater to a spectrum characteristic of terrestrially derived DOM. Microbial uptake of bio-labile DOM and leaching of humic like substances from vegetated wetland cells were the predominant processes involved in this transition. This transition coincided with an increase in the formation rates of O and DOM and in the steady state concentration of O.
人工湿地通过阳光产生的活性氧物质进行光降解，具有降解多种新兴关注污染物的能力。溶解有机物（DOM）是光降解的关键中间体，因为它会影响活性氧物质的产生。在这项研究中，对人工湿地处理废水的 DOM 的光化学行为进行了表征。使用 SUVA、光谱斜率比、激发发射矩阵荧光光谱（EEMs）和质子核磁共振（H NMR）对全水样和分级 DOM 进行了表征。通过测量羟基自由基（OH）、单线态氧（O）和 DOM 的三重激发态（DOM）的形成速率和稳态浓度来评估光反应性。结果表明，废水从微生物源蛋白样 DOM 转变为具有更高芳香度的陆地 DOM。尺寸排阻色谱法显示，植被湿地出水 DOM 中较大分子量的分数增加了 18%。此外，与未经处理的废水相比，湿地出水 DOM 的 H NMR 光谱中芳香区的比例增加了 32%。H NMR 分析还表明，湿地出水 DOM 的复杂性增加。EEMs 中蛋白样峰 T（Ex/Em：278/342nm）的荧光强度分数从未经处理的废水到湿地出水减少了 16%。激发发射光谱中峰 T（Ex/Em：278/342nm）和峰 A（Ex/Em：245/460nm）、C（Ex/Em：336/435nm）和 M（Ex/Em：312/400nm）的荧光百分比之间存在负相关，证实了从纯废水光谱向陆地来源 DOM 特征光谱的转变。微生物对生物可利用 DOM 的吸收和植被湿地细胞中腐殖质样物质的浸出是这一转变的主要过程。这种转变与 O 和 DOM 的形成速率增加以及 O 的稳态浓度增加相一致。
