Characterizing temporal and spatial variability of watershed dissolved organic matter and disinfection byproduct formation with fluorescence spectroscopy.

摘要

Dissolved organic matter (DOM) is important for drinking water utilities, because it serves as precursor material in the formation of disinfection byproducts (DBPs). Over the past 10 years, Front Range utilities have reported an increase in DOM in their primary drinking water sources. The reasons for the increase are not well understood, though potential hypothesis include changes in land use, urban growth and development, climate change and an ongoing pine beetle epidemic which has heavily impacted forests near watershed headwaters.;In this thesis, the physicochemical properties of DOM from northern Colorado watersheds and pine litter leachates were examined. The watersheds in the study originate in the Rocky Mountain region, where the majority of precipitation falls as snow and the main hydrologic event is snowmelt runoff. Spectral measures including fluorescence excitation and emission (EEM) and ultraviolet absorbance (UV) spectroscopy were utilized to analyze seasonal and spatial variability in DOM character from river and reservoir sites. Relationships between DOM measures and DBP formation were developed. Fluorescence measures provided additional information such as DOM origin, aromaticity and redox state not provided by traditional measures. Fluorescence parameters were strongly correlated with chlorine demand, total trihalomethane (TTHM) and haloacetic acid (HAA5) concentrations.;A parallel factor (PARAFAC) analysis model of the EEMs was developed for the two watersheds. A six component model was validated for filtered, coagulated, chlorinated and non-chlorinated watershed and pine leachate samples (n=494). The model characterized spatial and seasonal watershed DOM variability and provided information on fluorophores originating from a large scale mountain pine beetle epidemic in the watershed. Four humic-like components, one PP-TYR-like component and one tryptophan-like component were identified. Humic-like components were strongly correlated to chlorine demand, TTHM and HAA5 concentrations formed after 24 hours, while the PP-TYR-like and tryptophan-like components did not show correlations.;This thesis shows that fluorescence parameters may be used to develop relationships between watershed DOM character and TTHM and HAA5 concentrations. Fluorescence measures and PARAFAC analysis provide information to improve the understanding of the manageable fraction of DOM in respect to removal via coagulation and DBP formation and can facilitate watershed management and treatment decisions.