27-19 Geologic and Urban Controls on Municipal Contamination in Springs and Surface Water in Austin, Texas

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 92

Presenting Author:

Grace Castle

Authors:

Castle, Grace¹, Janelle, Alexander J.², Siegel, Helen G.³, Gary, Marcus O.⁴, McKinney, Tyson⁵, Shanahan, Timothy⁶, Banner, Jay L.⁷

(1) The University of Texas at Austin, Jackson School of Geosciences, Department of Earth and Planetary Sciences, Austin, Texas, USA, (2) The University of Texas at Austin, Jackson School of Geosciences, Department of Earth and Planetary Sciences, Austin, Texas, USA, (3) The University of Texas at Austin, Jackson School of Geosciences, Department of Earth and Planetary Sciences, Austin, Texas, USA; The University of Texas at Austin, Jackson School of Geosciences, Environmental Science Institute, Austin, Texas, USA, (4) The University of Texas at Austin, Jackson School of Geosciences, Bureau of Economic Geology, Austin, Texas, USA, (5) City of Austin, Department of Watershed Protection, Austin, Texas, USA, (6) The University of Texas at Austin, Jackson School of Geosciences, Department of Earth and Planetary Sciences, Austin, Texas, USA, (7) The University of Texas at Austin, Jackson School of Geosciences, Department of Earth and Planetary Sciences, Austin, Texas, USA; The University of Texas at Austin, Jackson School of Geosciences, Environmental Science Institute, Austin, Texas, USA,

Abstract:

Municipal inputs from aging or failing drinking water and wastewater infrastructure can contaminate relatively pristine natural waters. In this study, we sampled springs and surface water in three aquifers (Lower Cretaceous Edwards Limestone, Upper Cretaceous Buda Limestone, and Tertiary Colorado River Alluvial Terrace) in Austin, Texas, each with varying levels of urbanization and land use. Building on previous studies that demonstrate how differing urbanization extents and residence times influence municipal water-surface water interactions, we hypothesized that springs behave differently from surface water and that spring behavior varies across geologic formations.

Spring and surface water samples were analyzed for dissolved ions, per- and polyfluoroalkyl substances (PFAS), Sr isotopes, and water isotopes. We applied a mixing model to quantify municipally sourced constituents in natural waters and used water isotopes to estimate residence time and recharge time.

We found variable municipal contamination across aquifers and heterogeneity among springs within the same aquifer for specific contaminants and amounts of contamination. To estimate residence time using water isotopes, we used Edwards Limestone samples and surface water samples as endmembers. Water isotopes were similar among Edwards Limestone samples but had more variation in the Tertiary Colorado River Terrace and Buda Limestone. Springs in the Tertiary Colorado River Terrace had the highest concentrations of nitrate, chloride, and PFAS, indicating more influence from municipal inputs. Edwards Limestone springs were the least impacted by municipal inputs and had low PFAS concentrations due to limited urbanization and extensive land protection. The three springs sampled in the Buda Limestone had varying PFAS concentrations and compound types, indicating unique point sources of contamination. These findings demonstrate the impacts of urbanization, infrastructure failure, and localized geology on water quality in natural springs and surface waters. We show the importance of legislation for protection of vulnerable aquifer systems, as the most protected aquifer had the least impacted springs.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10651

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