[Abundance and Fluorescent Components of Dissolved Organic Matter Affected by Land Use in a Drinking Water Source]

Regional concentrations, fluorescent components, and sources of dissolved organic matter (DOM) in a drinking water source in Chaobai River across seasons were investigated here using fluorescence excitation-emission matrices, parallel factor analysis, and fluorescence indexes. Five fluorescent-DOM components were identified, including two microbial humic-like components and one autochthonous tyrosine-like, one reduced quinone-like, and one terrestrial humic-like component. DOM was mainly derived from microorganisms. The farmland-dominated region showed the highest DOM concentration and significantly lower maximum fluorescence intensities (F_max) of almost all fluorescent components than those in the forest-dominated region. The region dominated by urban lands exhibited obviously lower DOM concentrations than those in the farmland-dominated region and lower F_max values of fluorescent components than those in the forest-dominated region. No interaction was found between land use and season when considering their effects on DOM. Season had a significant influence on the humification degree of DOM. This study shows that agricultural land use had a greater impact on DOM than that of forests and urban areas, and the increased riverine DOM resulting from farmland was mainly non-fluorescent parts.