Caffeine as a Pollution Marker for Shallow Groundwaters in a Peri-Urban Area of Campinas / São Paulo – Brazil

Abstract The presence of emerging contaminants, including caffeine, in groundwater can represent an anthropogenic contamination that can impact human health. The present research aims to use caffeine as a wastewater pollution marker of shallow groundwaters in the peri-urban area of Campinas/SP. For a better evaluation of caffeine as an anthropogenic marker, more conventional markers were also analyzed, such as Cl-, NO3-, K+, B, NH4+, NO2- and DOC, and physicochemical parameters such as pH, Eh and EC. Two samplings campaign were done, the first in April (wet season) and the second in August 2019 (dry season), where 18 domestic wells, one sample from the river and one sample from an abandoned meander were selected points to collect water for physicochemical analysis. Nine wells and an abandoned meander waters were selected for the analysis of caffeine. Results show correlations between NO3- and Cl- indicating apport of domestic septic tanks sewage in groundwater. Caffeine, however, was detected in three samples and quantified in one during the wet season and was detected in two samples and quantified in one during the dry season. In the area, caffeine and nitrate have opposite behavior due to reducing conditions of the environment. The study area is rich in dissolved organic carbon, so the conditions for caffeine conservation are not ideal, because it degrades rapidly in groundwaters rich in bacteria and organic matter. Even in this scenario, caffeine was detected in groundwater in the study area, providing unambiguous evidence of anthropogenic pollution of the phreatic aquifer.