Mapeamento da fragilidade ambiental de íons fluoreto na macrorregião Verdes Campos/RS

Abstract

Groundwater is of utmost importance for population supply in Brazil, especially in areas with limited access to public water supply systems. Through the percolation of the surrounding geology, groundwater can carry pathogens and chemical contaminants such as fluoride, arsenic, nitrate, manganese, among others, which can pose health risks. Among these, fluoride ions (F- ) stand out, playing a crucial role in the prevention of dental caries when in concentrations ranging from 0.5 mg/L to 1.5 mg/L. However, when found in drinking water at concentrations above 1.5 mg/L, it can lead to adverse conditions such as dental or skeletal fluorosis, compromising the quality of life of populations relying on this water resource. Federal legislation follows WHO standards regarding fluoride ion limits, which is set at 1.5 mg/L. However, in Rio Grande do Sul, cases of dental fluorosis have led to the publication of more restrictive legislation than the federal one. Through Ordinance No. 10/1999, the limit was changed to 0.9 mg/L of fluoride in drinking water. Thus, the objective of this work was to demonstrate, through environmental fragility maps, the most vulnerable areas to fluoride contamination in the Verdes Campos macroregion, located in the state of Rio Grande do Sul. Initially, surveys and analyses of underground wells in the region were carried out, obtained from the VIGIAGUA portal, in the VIGIFLUOR section, to identify the areas with the highest contamination from 2014 to 2022. Subsequently, with the aid of QGIS software, vector layers such as land use and occupation (MapBiomas, 2023), geological formations (CPRM, 2023), population density (IBGE, 2022), and hydrology (SEMA, 2023) were included, and respective scores were assigned for each layer of interest. The maps were interpolated after assigning individualized weights based on the previously identified most affected areas, generating an environmental fragility map. The overall fragility map of fluoride ions provided a similar result compared to the VIGIFLUOR analyses, confirming the method's efficiency. With this work, it is hoped that the data from this research can aid decision-making regarding possible new sites for tubular well installations, improving the population's quality of life and preventing environmental damage due to excessive fluoride ion presence.