Brasilia

Tracing and tracking wastewater-derived substances in freshwater lakes and reservoirs: Anthropogenic gadolinium and geogenic REEs in Lake Paranoá, Brasilia

A significant increase in anthropogenic gadolinium (Gd) in Lake Paranoá, Brasilia, between 2012 and 2013, was detected, serving as a tracer for wastewater-derived substances such as pharmaceuticals. This finding highlights the potential of rare earth element (REE) geochemistry as an inexpensive method to monitor water quality, particularly for reservoirs like Lake Paranoá, which may serve as future drinking water sources. The study analyzed total and dissolved REE and uranium concentrations during dry and wet seasons, revealing distinct M-type lanthanide tetrad effects and large positive Gd anomalies, with the latter likely originating from wastewater treatment plant effluents due to the use of Gd-based contrast agents in medical imaging. Additional inputs, such as aeolian or fluvial sources, may contribute to the observed Ce anomaly.