Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 845, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2022.157300
Keywords
Constructed wetlands; Dissolved organic matter; Phototransformation; Reactive species; Bisphenol A
Categories
Funding
- National Natural Science Foundation of China [51778522]
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This study investigates the photochemical behavior of dissolved organic matter (WDOM) in free water surface flow constructed wetlands (CWs) under sunlight irradiation. The results show that solar irradiation can lower the molecular weight and aromaticity of WDOM, as well as weaken its light absorption. Reactive species produced from WDOM significantly enhance the photodegradation of Bisphenol A (BPA), a representative endocrine-disrupting compound.
Free water surface flow (FWS) constructed wetlands (CWs) have been broadly applied for polishing secondary treated effluents. Dissolved organic matter derived from FWS CWs (WDOM) plays key roles in contaminants transformations. Conversely, photodegradation could shape the quantity and quality of WDOM, thereby affecting its roles in the photol-ysis of organic micropollutants (OMPs). Nevertheless, whether and how solar irradiation-induced photodegradation modify the properties of WDOM, and the effects of WDOM on the photodegradation of OMPs remain unclear. This study elucidates the photochemical behavior of two WDOM isolated from field-scale FWS CWs for effluent polishing under simulated sunlight irradiation using spectroscopic tools and high-resolution mass spectra. Furthermore, the roles of WDOM in the photodegradation of Bisphenol A (BPA), as a representative endocrine-disrupting compound (EDC), were comprehensively investigated. Solar irradiation was demonstrated to lower the molecular weight and aro-maticity of WDOM, as well as weaken its light absorption. Ultrahigh-resolution mass spectra further confirmed that aromatic and unsaturated structures were susceptible to solar irradiation-induced photodegradation reactions. Subse-quently, less aromatic and more saturated structures eventually formed under sunlight irradiation, consistent with the result from spectroscopic characterization. The reactive species produced from WDOM significantly enhanced the photodegradation of BPA with the kobs noticeably increasing 4-fold compared with the kobs for direct photolysis. Additionally, 3WDOM* was identified as the dominant reactive species leading to the photolysis of BPA in the presence of WDOM. These findings improve understanding of the phototransformation behavior of WDOM under sunlight irra-diation and the roles that WDOM plays in the photochemical fate of coexisting OMPs in CWs treatment systems.
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