Emerging Contaminants in Water Resources: Monitoring Gaps, Treatment Limitations and Governance Challenges in a Global Context with Insights from Portugal

This paper provides a systematic and comparative review of emerging contaminants in water resources, examining global trends in occurrence, detection technologies, treatment strategies and regulatory responses, with a particular focus on the Portugal context. Following PRISMA 2020 guidelines, peer-reviewed studies published between 2020 and 2025 were critically assessed to identify patterns of contamination, monitor-ing gaps and technological readiness levels. Results indicate an increasingly frequent presence of pesticides, antibiotics, antidepressants and nutrients in surface water, groundwater and wastewater systems. Advanced analytical techniques, particularly liquid chromatography coupled with high-resolution mass spectrometry stands out as the main detection technique, allowing the identification of trace levels of compounds and the characterization of diffuse sources of contamination associated with agricul-ture, urban and industrial effluents. However, significant asymmetries persist between international and Portuguese research, especially regarding systematic monitoring networks and integrated risk assessment approaches. Conventional water/wastewater treatment plants show limited removal efficiency, while advanced oxidation processes, adsorption technologies and microalgae-based systems demonstrate promising but variable performance depending on scale and operational maturity. The findings high-light critical gaps between scientific advances and regulatory implementation, empha-sizing the need for strengthened monitoring frameworks, technology scale-up strate-gies and improved integration between science, governance and sustainability policies to ensure resilient water resource management in line with the Sustainable Develop-ment Goals.