Effect of a dam on the optical properties of different-sized fractions of dissolved organic matter in a mid-subtropical drinking water source reservoir

• Published in: The Science of the total environment Vol. 598; pp. 704 - 712
• Main Authors: Sun, Qiyuan, Jiang, Juan, Zheng, Yuyi, Wang, Feifeng, Wu, Chunshan, Xie, Rong-rong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.11.2017
• Subjects: CDOM; China; Dam; Drinking Water - chemistry; Drinking water source; EEM; Organic Chemicals - analysis; Phytoplankton - metabolism; Rivers; Size fraction; Spectrometry, Fluorescence; Tangential ultrafiltration; Water Supply; CDOM; Dam; Tangential ultrafiltration; Size fraction; EEM; Drinking water source
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.04.175

The presence of a dam on a river is believed to have a key role in affecting changes in the components of the chromophoric dissolved organic matter (CDOM) in reservoirs. However, questions remain about the mechanisms that control these changes. In this study, we used tangential ultrafiltration, fluorescence spectrum and phytoplankton cell density detection to explore the impacts of a dam on the CDOM components in the Shanzai Reservoir, a source of drinking water. The results demonstrated each CDOM size fraction comprised two main components, namely C1 (protein-like substance) and C2 (humic-like substance). The C1 content had a higher value in areas with slow flow than in the normal river channel, while the C2 contents were generally stable in the flow direction. The topography of the reservoir site affected the structure of the CDOM components based on changes in the hydraulic conditions caused by the dam. The variations in the CDOM components, hydraulic parameters and fluorescence indices in the river flow direction indicated that the contribution of the phytoplankton to the CDOM content increased as the distance to the dam decreased, phytoplankton metabolism enhanced C1 content of the 1–10kDa molecular weights range fraction. Further, the contributions of different phytoplankton biomass to C1 proved that the dam changed the hydraulic conditions, had secondary effects on the metabolism of the phytoplankton, and resulted in changes in the structure of the CDOM components. [Display omitted] •Slow flow reservoir areas had a higher protein-like content and a lower mean molecular weight than the river.•The phytoplankton contribution to CDOM increased as the distance to the dam fell.•Phytoplankton metabolism mainly enhanced the protein-like part of the 1–10kDa molecular weights.•The presence of the dam resulted in a decrease in the degree of CDOM humification.