Dissolved organic matter characteristics of urban stormwater runoff from different functional regions during grassy swale treatment

In this study, the water purification performance of grassy swales for treating stormwater runoff was evaluated using a simulated experimental device. The binding properties of dissolved organic matter (DOM) in stormwater runoff samples from Beijing were measured by ultraviolet visible absorbance spectroscopy and excitation-emission matrices, combined with parallel factor analysis (PARAFAC). The concentrations of total nitrogen and phosphorus were significantly decreased after treatment by grassy swales: 50%-95.23% of total suspended solids and total organic carbon were removed, respectively. Additionally, the removal of heavy metal ions was 30.95%-97.39%. The spectral parameters indicated that humification and aromaticity of DOM would be greatly increased by grassy swale treatment. Two humic-like components and one protein-like component were identified in the runoff DOM using excitation-emission matrices coupled to PARAFAC. With progressive grassy swale treatment, the content of humic-like components increased and protein-like substances gradually decreased. Two-dimensional correlation spectroscopy demonstrated that the effluent DOM of grassy swale samples displayed different binding sites for Cu (II). Thus, the binding sequencing of Cu (II) with DOM fluor-ophores can be greatly influenced by grassy swale treatment. The results may provide a solid foundation for the treatment of urban runoff pollution.