title: Sunlight-induced changes in chromophores and fluorophores of wastewater-derived organic matter in receiving waters--the role of salinity.
abstract: Wastewater-derived organic matter (WOM) is an important constituent of discharge to urban rivers and is suspected of altering the naturally occurring dissolved organic matter (DOM) in water systems. This study investigated sunlight-induced changes in chromophores and fluorophores of WOM with different salinities (S = 0, 10, 20 and 30) that were collected from two wastewater treatment plants (WWTP-A and WWTP-B). The results showed that exposure to sunlight for 5.3 × 10(5) J/m(2) caused significant decreases in UV254-absorbing WOM (45-59% loss) compared to gross dissolved organic carbon (<15% loss). An increase in salinity accelerated the overall photo-degradation rates of the UV254-absorbing chromophores from both WOM and natural DOM. In addition, irradiated WOM at a higher salinity had a larger molecular size than that at a lower salinity. However, natural DOM did not display such behavior. Parallel factor analysis of the excitation-emission matrix determined the presence of two humic-like components (C1 and C2) and two protein-like components (C3 and C4). All the components in WOM followed second-order kinetics, except for the C4 component in WWTP-A, which fit zero-order photoreaction kinetics. The photo-degradation of the C1 component in both WWTPs appeared to be independent of salinity; however, the photo-degradation rates of the C2 and C3 components in both WWTPs and C4 in WWTP-B increased significantly with increasing salinity. In comparison, the photo-degradation of the C1 component was significantly facilitated by increased salinity in natural DOM, fitting first-order photoreaction kinetics. As such, the current knowledge concerning the photo-degradation of naturally occurring DOM cannot be extrapolated for the understanding of WOM photo-degradation.
authors: SYSU-HKUST Research Center for Innovative Environmental Technology, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University), Guangzhou 510275, PR China.
authors: Xiaofang
authors: X
authors: Yang
authors: SYSU-HKUST Research Center for Innovative Environmental Technology, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University), Guangzhou 510275, PR China. Electronic address: mengfg@mail.sysu.edu.cn.
authors: Fangang
authors: F
authors: Meng
authors: SYSU-HKUST Research Center for Innovative Environmental Technology, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University), Guangzhou 510275, PR China.
authors: Guocheng
authors: G
authors: Huang
authors: Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University), Guangzhou 510275, PR China.
authors: Li
authors: L
authors: Sun
authors: Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University), Guangzhou 510275, PR China.
authors: Zheng
authors: Z
authors: Lin
mesh_terms: D002244:Carbon / Q000032:analysis; D004777:Environment; D007700:Kinetics; D049408:Luminescent Agents / Q000528:radiation effects*; D009930:Organic Chemicals / Q000737:chemistry*; D010782:Photolysis / Q000528:radiation effects; D054712:Salinity; D013050:Spectrometry, Fluorescence; D013472:Sunlight; D014466:Ultraviolet Rays; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000528:radiation effects*; D018508:Water Purification
chemical_list: D002244:Carbon; D049408:Luminescent Agents; D009930:Organic Chemicals; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Dissolved organic matter (DOM); Parallel factor analysis (PARAFAC); Photo-degradation; Wastewater-derived organic matter (WOM)