Tracking pharmaceutical contamination in coastal aquifers: An integrated modeling framework for source identification and risk management in the Campina de Faro aquifer system (Portugal)

The occurrence of emerging persistent pharmaceuticals (PPPs) in groundwater (GW) systems is a growing environmental concern, particularly in areas under combined urban and agricultural pressure. This study applies an integrated numerical modeling approach to assess the fate and potential sources of PPPs in the Campina de Faro aquifer system (CF), southern Portugal. To simulate the hydrogeological dynamics of the study area, a GW flow model was developed and calibrated using MODFLOW-2005. Calibration was supported by field measurements and literature-derived hydrogeological parameters. Flow model outputs were used to perform backward particle tracking, enabling a probabilistic assessment of contaminant transport pathways and the identification of likely source areas. A reactive transport model was subsequently developed using MT3DMS to simulate the dispersion and fate of selected PPPs, incorporating processes such as advection, dispersion, and biodegradation. Moreover, a principal component analysis (PCA) was conducted which agrees with our modeling hypothesis, thus showing a discontinuity in the Cretaceous formation at the northwestern boundary of the aquifer system. PCA showed that some of the abstraction points are extracting from a different aquifer than previously believed, giving new insight into the conceptual understanding of the study area. The modeling framework demonstrates its effectiveness in delineating areas of contamination, potential sources, and characterization of PPP behavior in GW. This approach provides a valuable support tool for GW quality management and mitigation of risks associated with emerging contaminants such as PPPs in vulnerable aquifer systems.