Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Earth and Planetary Sciences

Language

English (en)

Date of Award

1-1-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Robert Criss

Abstract

This dissertation examines the physical hydrology and geochemistry of surface waters and shallow groundwaters in east-central Missouri, USA, to determine how runoff differs in flow and quality between urban and natural watersheds. The study employs high frequency in situ monitoring of relevant water quality parameters in tandem with lab analyses of major and minor elements and stable isotope concentrations to address degradation of watersheds by land development and other human activities. Chapter 3 of this dissertation compares three watersheds and their tributaries, each with differing levels of urban land use, which were monitored for more than one year to document their hydrologic and geochemical character. Urban streams were characterized by flashier responses to storm perturbations and had reduced baseflow components compared to rural streams. Rural streams had smaller hydrologic and geochemical variations, higher baseflow, and longer lag times following storm perturbations. Urban and suburban streams were commonly polluted with salts and nutrients, and chemical compositions could change rapidly. Continuous monitoring data demonstrate increased seasonal and diurnal variability in urban systems, and show that infrequent and arbitrary sampling regimes in both urban and rural systems can under- or overestimate loads by 100-fold. Chapter 4 examines regional boron: B) concentrations. In contrast to previous work that attributes B contamination of surface waters and groundwaters to wastewaters and fertilizers, this study found that the largest contributor of B to local waters was municipal drinking water used for urban lawn irrigation. Chapter 5, a comparative study of springs in east-central Missouri, establishes contaminant background levels in shallow groundwaters and quantitatively establishes that springs proximal to St. Louis and adjoining suburbs have the most degraded water quality. The impacted springs display the same water quality problems as urban surface waters including high Cl: > 230 ppm), low dissolved oxygen: DO; < 5 ppm), and high Escherichia coli: E. coli; > 206 cfu/100 mL). In addition, the residence times for contaminants typically range from a few months to two years and approximate stable isotope residence times. Chapter 6 discusses a novel technique to determine the subterranean environment of groundwaters using field measurements of DO and pH. Springs draining vadose cave passages have higher DO and pH values than "phreatic" springs that have no known cave passage because of the equilibration of DO with overlying cave air and the simultaneous degassing of dissolved CO2. Degassing processes also affect the saturation state of minerals such as calcite, with cave springs having the highest degree of saturation with respect to calcite. Taken together, these chapters provide a unique archive of regional water hydrology and geochemistry, and demonstrate previously unknown sources and transport mechanisms for several chemical constituents.

Comments

Permanent URL: http://dx.doi.org/10.7936/K7N014KS

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