Young, Kirby Lynn (2018-05). Biogeochemistry of Urban, Suburban, and Rural Ponds and Lakes in South-Central Texas. Master's Thesis.
Urban lotic surface waters have been extensively studied due to reported increases in their alkalization and dissolved organic carbon (DOC). However, urban lentic surface waters, which are subject to the same United States Environmental Protection Agency and Texas Commission on Environmental Quality (TCEQ) standards and present opportunities for human recreation and interaction, have received less attention. This study analyzed 24 urban, suburban, and rural lakes and ponds in South-Central Texas for Escherichia coli (E. coli), biogeochemical parameters, and a variety of metals within sediment. Additionally, potential relationships between seasonality, land cover classifications, and the analyzed constituents were explored. Seven of the 24 sampling sites had annual E. coli geometric means that exceeded the TCEQ's Primary Contact Recreation Standard of 126 most probable number (MPN) 100 mL^-1 but none exceeded the Secondary Contact Recreation I Standard of 630 MPN 100 mL^-1. Seasonally, the fall and spring had the highest number of sites that exceeded both of these standards. The biogeochemical parameters analyzed included pH, electrical conductivity, NOv3-N, NHv4-N, dissolved organic nitrogen, POv4-P, total suspended solids, DOC, SUVAv254, and BODv5. All of the parameters, except BODv5, were found to have statistically significant relationships with seasonality. None of the metals analyzed exceeded the TCEQ Texas Risk Reduction Program Tier 1 Sediment Protective Concentration Levels. Select biogeochemical parameters and metals were found to be significantly correlated with four land cover classifications, including grassland, forest, developed, and water. E. coli concentrations were not found to be significant correlated with any land cover. The findings from this study emphasize the importance of monitoring lentic surface waters, especially due to the increased E. coli concentrations and the impact of seasonality on water quality conditions.