Spectral evaluation of watershed DOM and DBP precursors

Abstract

Dissolved organic matter (DOM) quantity and character from eight locations, including rivers and managed‐flow sites, within two northern Colorado Rocky Mountain watersheds were examined using fluorescence and absorbance spectroscopy to characterize changes in DOM quantity and quality. River sites exhibited strong seasonal variability, containing higher concentrations of more aromatic DOM during spring runoff. Reservoir‐influenced, managed sites had year‐round stability and were less aromatic compared with the rivers. Total trihalomethane formation potential (TTHMFP) was used as a measure of DOM chlorine reactivity. Fluorescence compositional metrics (fluorescence index [FI] and Peak C/UV340 ratios) correlated with TTHMFP yields. River sites showed increased TTHMFP concentrations during runoff but little change in TTHMFP yield. Managed sites showed little seasonal variation in both TTHMFP and TTHMFP yield. The results show that fluorescence parameters provide additional information on DOM character not available from conventional measures and may be useful in facilitating watershed management and treatment decisions.