Application of Pb isotopes to the identification of geogenic and anthropogenic sources in groundwaters and surface waters in a world-class coal deposit area and associated thermoelectric power plant in Candiota, southern Brazil

The use of lead isotopes has been widely applied to identify contamination sources in nature. The present study aims to investigate the Pb isotope signature of surface and groundwaters in the region of Candiota, southern Brazil, where the largest mineral coal field in the country is found to identify geogenic and anthropogenic sources of Pb. Sampling was performed following an environmental monitoring program carried out in the area surrounding a thermoelectric power plant. Isotope and concentration analyses of Pb were performed also in a variety of geological materials, such as coal, sandstone, and metasandstone, to identify geogenic sources of Pb. For the identification of anthropogenic sources, sampling covered all the activities developed in the area, including farming, marble mining, and urbanization, by measuring Pb isotopes on samples of coal ash, marbles, sediments, and pesticides used in rice and soy cultivation. The results obtained for 206 Pb/ 207 Pb were compared to data from the literature on anthropogenic sources of contamination worldwide. The data assessment showed that, regarding geogenic sources of Pb, the surface waters are influenced by coal in comparison to groundwaters which possess a signature matching sandstones as well as signatures similar to the ones from surface waters in some locations. As for anthropogenic sources, the study identified sources of Pb connected to marble mining, coal ash, and pesticides and their possible impact on the isotopic composition of waters and sediments analyzed in the region. Finally, the isotopic signature 206 Pb/ 207 Pb of groundwaters from two monitoring wells indicate also the influence of fuels and domestic sewage in their composition, showing, for the first time, that the area has a complex distribution of Pb both by geogenic and anthropogenic sources.