Hydrochemistry, δD and δ18O to explain the distribution of water quality in a karst setting in the semi-arid region of Northeast Mexico

Abstract

Characterization of the groundwater flow systems can be used in conjunction with the geochemical evolution of groundwater to assess water–rock interaction processes, time of residence, and the regional hydrogeochemical evolution system. To identify the regime of groundwater flow, we consider it is essential to localize the geographic components of the hydrologic cycle, where the geologic environment determines the functional areas such as the recharge and discharge areas and the dynamics of water availability of the aquifer, as well as water quality. In this paper, we analyzed the groundwater flow systems on a section of chalky rocks, known as Plataforma Valle-San Luis Potosí (PVSL), located in the state of Tamaulipas, Northeast Mexico. The groundwater from the study area has dissolved Ca 2+ and HCO 3 − as dominant ions; average concentrations are 118.9 and 253.9\xa0mg/L, respectively. Thought to be derived from calcite dissolution, basically under the influence of the massif of the Sierra Madre Oriental, a karst Quaternary environment denominated El Abra Formation, a sedimentary rocks geology that dominates the regional geology. We used the cluster analysis to classify the primary element concentrations in two groups and three subgroups, where we could identify a local, intermediate, and regional flow. Defining the evolution of groundwater from recent waters on Ca 2+ to HCO 3 − and dominance of SO 4 −2 to waters with more residence period, associated with the dissolution of gypsum from the Guaxcama Formation. That s was corroborate by utilization of δD and δ18O data which allow the identification of the recharge areas with mean values from −\xa07.94 δ18O (‰) and 53.84 δD (‰) on recharge areas, and −\xa08.19 ‰ δ 18 O and 57.83 ‰ δD on intermediate flow. This result contributes to describe the geochemical process of groundwater and how it interacts with geological formations with El Abra Formation, the most crucial geological-water unity for the study area.