Evaluation of the sodium concentration in the groundwater of the Aquifer Systems of the State of Rio Grande do Sul, Brazil

Abstract

Abstract Sodium in drinking water is not a health concern for most people, but may be an issue for someone with hypertension, congestive heart failure or on a sodium-restricted diet. This work evaluated sodium concentration data in wells of the main aquifer systems in the state of Rio Grande do Sul (RS) according to the potability standard established by Ordinance No. 888 of 2021 of the Brazilian Ministry of Health. Furthermore, an analysis of sodium concentrations in relation to to the recommendation of the U.S. EPA and other countries on sodium concentration in drinking water less than 20 mg/L for individuals on a sodium-restricted diet (500 mg/day). The human health risk of sodium was assessed by calculating the non-carcinogenic hazard quotient from the US EPA Human Health Risk Assessment. In all, 4,687 hydrogeochemical data from tubular wells that capture water in the Permian Aquitards (AP), Crystalline Basement Aquifer System (SAEC), Guarani Aquifer System (SAG), Coastal Quaternary Aquifer System (SAQC), Palermo - Rio Bonito Aquifer System (SAPRB) and Serra Geral Aquifer System (SASG). More than 100 wells exceeded the maximum allowable amount of sodium in water from Ordinance No. 888 of 2021 of the Brazilian Ministry of Health. All aquifer systems have more than 30% of wells with sodium values above the U.S. EPA recommendation on sodium concentration in drinking water less than 20 mg/L for individuals on a sodium-restricted diet (500 mg/day). Ten wells in RS showed indications of non-carcinogenic risk.