Occurrence and temporal changes of pharmaceuticals in the Warta River in Poland during and after the COVID-19 pandemic.

This research aimed to assess the impact of the COVID-19 pandemic on pharmaceutical concentrations in surface water. The Warta River (western Poland) was studied at points upstream and downstream of the treated sewage outflow. Ten pharmaceuticals were analyzed in 12 sampling campaigns during the pandemic (February 2020 - April 2021), and 3 during the post-pandemic period (November 2024 - January 2025) to assess their long-term impact. The results revealed a significant increase in pharmaceutical concentrations near the outflow of treated sewage (range 1.53-20.47 µg/L), confirming that it is the main source of these micropollutants in the environment. Moreover, the concentration increase in the river, overlapped with successive waves of the COVID-19 pandemic. This made it possible to identify patterns of society's behavior. During lockdowns, preventive and psychotropic drug concentrations increased in the river. These indicate that higher consumption of these pharmaceuticals maybe associated with worse mental well-being and a desire to protect against the virus. However, the concentrations of antibiotics and cardiological drugs decreased, which was linked to more difficult access to doctors and protection from the virus by avoiding the health center. During the post-pandemic period psychotropic drug concentrations increased significantly, suggesting a significant deterioration in society's mental health.