Changes in the characteristics of dissolved organic matter released from sediment according to precipitation in the Namhan River, South Korea.

Abstract In this study, changes in the properties of dissolved organic matter (DOM) released from sediments into water layers were investigated. To analyze the spatial and temporal variation in dissolved organic carbon (DOC), sediment and bottom water samples were collected upstream of the Gangcheon, Yeoju and Ipo weirs of the Namhan River during the rainy and non-rainy seasons. Vials containing the sediment and bottom water samples were incubated for seven days at 20 ℃ in the dark. Thereafter, the DOC concentration of the supernatant was analyzed at 0, 3 and 7 days of incubation. The results show that the change of bottom water DOC concentration resulted from the DOC released from the sediments. The initial DOC was significantly correlated with precipitation (p = 0.0042) and residence time (p = 0.0473). Furthermore, fluorescence analysis revealed that the DOM contained a significant quantity of hydrophilic and low-molecular-weight (LMW) organic matter in non-rainy season, and higher levels of hydrophobic and high-molecular-weight (HMW) organic matter were observed during the rainy season.