MULTI ISOTOPIC AND NOBLE GASES APPROACH TO UNDERSTAND THE GROUNDWATER FLOW CONDITIONS AND RECHARGE IN AÇU AQUIFER IN THE POTIGUAR BASIN

Abstract

In the Brazilian Northeast, groundwater represents the main source of water. In the scenario of climate change and demographic growth in semi-arid regions, knowledge about flow conditions, storage and hydrogeochemical evolution of groundwater contributes to better management of water resources in these regions. The record of overexploitation and salinization in the Açu Aquifer, located in the Potiguar Sedimentary Basin (BSP), in the states of Ceará and Rio Grande do Norte, creates the necessary alert for new studies to be carried out in the region. Through the integration of hydrogeochemical data, environmental isotopes (´2H, ´18O, ´13C and 14C) and noble gases (He, Ne, Ar, Kr, Xe), the present study aims to understand, the flow, storage and residence time conditions of groundwater of the Açu Aquifer, as well as understanding past climatic conditions at the time of its recharge. The flow and confinement systems of the Açu Aquifer present a consistent pattern represented by increased residence times from the recharge zone located on the edge of Chapada do Apodi. Current climate patterns in the region differ from past conditions during the Holocene/Pleistocene transition, between 4 and 7°C cooler, identified in previous studies. Therefore, with the use of climate tracers, such as stable isotopes and noble gases, it is expected to understand the climate conditions during groundwater recharge, enabling a better understanding of the region's paleoclimatic framework. Furthermore, interpretations regarding the residence time of these waters, mixing with underlying saline waters contribute to the knowledge of the flow and management systems of this aquifer.