Source identification of groundwater salinization within a localized aquifer system in Texas

This study investigates an abrupt groundwater salinization event in a localized aquifer system in North Central Texas. Salinization increases observed in this system are potentially related to petroleum production, agriculture/livestock activity or interaction with deeper groundwater. Analysis of hydrogeochemical data revealed unusual Ca-Mg-Cl waters with little HCO3- or Na+. Cl- proportion correlated directly with TDS. Leaching of soil samples revealed direct correlation between soils-derived-TDS and distance from nearest oil well. Resistivity measurements identified a shallow high-conductivity zone extending down-gradient from the well. Indications of conductive material were observed in the near surface (0--10m) in the 2D resistivity profile. Low NO3- levels indicated that agriculture and livestock contributions to salinization are unlikely. Minimal SO42- and low Na+/Cl- ratios suggest little contribution from evaporites. High TDS and low Na+/Cl- ratios infer petroleum production activities as the likely contributor to groundwater quality reduction at this site. Whether these fluids arise from the oil production interval or from intervening brackish aquifers is still unknown.