For my honors thesis I studied the influence of human activities on the contamination of groundwater in the Bull Creek watershed of Austin, Texas. I collected springwater samples from sites classified as “urban” or “rural” based on impervious cover estimates and analyzed them for strontium (Sr) isotopes and major ion concentrations. I used Sr isotopes because there is a significant difference in the Sr isotope composition (87Sr/86Sr values) between municipal water and local groundwater. Municipal water, obtained from the Colorado River dissolves Pre-Cambrian gneisses and granites of the Llano Uplift and has relatively high 87Sr/86Sr values. Local groundwater dissolves Cretaceous Carbonate rock and is characterized by having relatively low 87Sr/86Sr values. Increasing 87Sr/86Sr values with increasing concentrations of anthropogenic species (e.g. F, SO4, NO3) suggest that groundwater in urban portions of the watershed was impacted by human activities. Understanding the effects of urbanization on groundwater quality in this study area will help identify high-priority springs for water quality remediation.
Advisor: Jay Banner