Abstract
Rivers carry dissolved organic matter (DOM), which influences nutrient cycling, pollutant transport, and the distribution of microbial communities within aquatic ecosystems. This research investigates dissolved organic carbon (DOC) diversity and its impact on water quality within the Tajan River watershed. Sampling was conducted from March 2023 to February 2024 at ten stations, where key parameters including temperature, dissolved oxygen (DO), turbidity, electrical conductivity (EC), chemical oxygen demand (COD), DOC, total phosphorus (TP), total nitrogen (TN), and chlorophyll-a were measured using standard methods. Fluorescence was measured in the spectral range 200-550 nm excitation and 200-450 nm emission. Seasonal analysis revealed that EC, temperature, turbidity, TP, and specific ultraviolet absorbance (SUVA) were lower in winter; while COD and DOC concentrations were lowest in spring. The highest levels of TN and chlorophyll-a occurred in spring. Station 7 showed elevated concentration of EC, temperature, DOC, COD, and TP compared to other sites. Using the PARAFAC technique, seven fluorescence component (C1-C7) were identified, with C1 representing visible humic substances. C1 exhibited strong positive relationships with temperature, chlorophyll-a, TN, TP, UV254, and COD. The EEM-PARAFAC method effectively evaluates the link between the fluorescent components of DOM and water quality parameters, demonstrating its potential for surface water quality monitoring.