Hydrochemical and contamination evolution of Rio Bonito aquifer in the Carboniferous region, Paraná Basin, Brazil

Groundwater is an essential natural reserve of fresh water in the world. However, population and economic growth in many countries has caused the contamination of many aquifers. Water crises make significant any study of the Paraná Basin aquifers, composed of several geological formations with high capacity of storage and transmission of water. In this context, Rio Bonito aquifer is in part located in the Carboniferous Region of Santa Catarina state (Brazil) and in the Araranguá Hydrographic Basin. The carboniferous region is known for coal mining and minimal care for the environment which led to damaging consequences. In this study, the interpretation of chemical data from nine wells monitored by 'Grupo Técnico de Assessoramento' (GTA, Relatório de Monitoramento dos Indicadores Ambientais (Internal technical reports referent the years 2006–2018), vol 1. Ação Civil Pública n. 93.8000.533-4. Processo de cumprimento de sentença n. 2000.72.04.002543-9. Criciúma, Brasil, 2018) was performed with binary variation diagrams, photo interpretation and comparison with local geology. This resulted in the identification of four groundwater groups with different hydrogeochemical characteristics, due to processes of water/rock interaction and contamination by the coal mines. The petrographic analysis defined that the sandstones from top coal layer of Rio Bonito aquifer is of the fractured type. The results indicate that the Rio Bonito aquifer in the studied region is contaminated by coal mining with high levels in limited areas, but only in one well. Groundwater quality is monitored in the Rio Bonito aquifer, which is very important for the management of water use and mitigation of existing contamination, but also to prevent contamination of other areas.