Observations of groundwater-surface water exchange effects on emerging pollutants in a subtropical catchment.

The occurrence of emerging pollutants (EPs) in aquatic environments is a major threat to natural ecosystems and human health, but the connections between EPs in surface water and groundwater have been largely unexplored. Here, a total of 38 EPs, including antibiotics, per- and poly-fluorinated alkyl substances, and herbicides were monitored in both surface water and adjacent groundwater in the Jiulong River Basin of China. Thirteen different EPs were detected, with atrazine, sulfamethoxazole and perfluorooctanoic acid identified as priority pollutants based on a novel holistic scoring method that integrated concentration levels, occurrence frequency, and environmental and human health risks in surface water-groundwater systems. Clear connections between the EPs in surface water and groundwater were apparent, demonstrated through principal component analysis and hierarchical clustering. Agricultural activities appear to be the main EP sources, with dissolved oxygen playing a significant role in the occurrence of EPs in both surface water and groundwater. The detected EPs can be well explained by the interaction between surface water and groundwater in combination with natural attenuation processes. These findings underscore the critical role of surface water-groundwater exchange in the fate of EPs within water systems, a factor often overlooked in prior EP analyses.