ASSESSMENT OF HYDROGEOCHEMISTRY AND GIS-BASED EVOLUTION OF GROUNDWATER QUALITY AND SALINITY IN THE SHALLOW AQUIFER OF SÃO JOSÉ DO NORTE, SOUTHERN BRAZIL

Abstract

Water salinization changes hydrogeochemistry, affects the quality and quantity of groundwater available for human consumption and its mitigation is time-consuming. A large brackish lagoon and the Atlantic Ocean surround the aquifer of the São José do Norte town (Brazil). Population and economic growth demand more groundwater for domestic and agricultural purposes, stressing the aquifer. Despise the aquifer’s social-economic status, potential impacts on the groundwater have not yet been substantially investigated. The aims of this study were to analyze the hydrogeochemistry of the São José do Norte aquifer, focusing on the search for salinization indicators, and to assess the groundwater suitability for human drinking and irrigation purpose. Ionic ratios, Piper and USSL diagrams were applied, such as new methods, as Seawater Intrusion Groundwater Quality Index (GQISWI) and the Groundwater Quality Index for human consumption (GWQIHC). The results showed that the groundwater is mostly calcium bicarbonate type and did not indicated salinization occurrence. The interior and the northern area had the highest ionic content and the lowest water quality values. Most of the samples contained at least one parameter above the maximum allowed concentration for drinking purpose according to water quality standards. High concentration of alkalinity, iron and hardness reduced the groundwater suitability for human consumption, requiring water treatment before ingestion.