Urban River Contamination Case Study: Spatial–Temporal Dynamics of Emerging Contaminants in the Fervença River (Bragança, Portugal)

Urban rivers are subject to multiple anthropogenic pressures, particularly those associated with wastewater discharges and diffuse inputs from urbanized catchments. This study investigates the occurrence and spatial–temporal patterns of emerging contaminants in the Fervença River (Bragança, NE Portugal), with a specific focus on the influence of the municipal wastewater treatment plant (WWTP). Three riverine sampling sites were selected to represent upstream rural conditions, urban influence, and downstream areas receiving WWTP effluent. An additional sampling point was included at the WWTP discharge. Water and sediment samples were collected during four campaigns: one dataset from 2018 and three sampling campaigns conducted in March, May, and September 2024.

The analyses targeted a set of pharmaceutical products using HPLC-MS. Physicochemical parameters were also recorded in situ. The results show (i) a marked increase in contaminant concentrations in the urban section, (ii) the persistent detection of certain pharmaceutical products downstream of the WWTP, indicating incomplete removal, and (iii) differences in contaminant profiles between water and sediments, suggesting specific partitioning behavior of the compounds and possible long-term accumulation in benthic compartments. Comparison of data from 2018 and 2024 suggests temporal variability potentially related to changes in urban water use patterns and treatment efficiency.

This case study highlights the vulnerability of small urban rivers to wastewater-related contamination and the importance of integrating sediment monitoring to capture the environmental persistence of emerging contaminants. Findings contribute to a better understanding of contaminant dynamics in urban systems and support evidence-based management strategies to mitigate chemical pressures in freshwater environments.