Pharmaceuticals with intrinsic environmental mobility are widely detected in rivers, estuaries, and oceans worldwide, underlining the need to prioritize and control those capable of long-range transport along river/estuary-to-sea pathways. The river-estuary continuum of Hong Kong, a representative coastal metropolis, was therefore selected to address this issue. This study integrated a persistence, mobile, and toxicity (PMT)-based priority control assessment with river/estuary-to-sea transport trajectory modeling to systematically evaluate high-priority pharmaceuticals along the river–estuary continuum. The results revealed that mobile pharmaceuticals were prevalent in the river-estuary continuum of Hong Kong, with nervous system agents predominating, averaging 69% and 75% in the dry and wet seasons, respectively. Over-the-counter medicines were the major contributors. Pharmaceutical levels correlated strongly with age-grouped population densities, while the relative importance of age groups varied across pharmaceutical classes. Among the target pharmaceuticals, 80% exhibited PMT properties, and caffeine, paracetamol, cetirizine, cimetidine, sitagliptin, and fexofenadine were identified as priority pollutants for river/estuary-to-sea control. These high-priority PMT pharmaceuticals could be subject to a longer-range transport to the South China Sea as indicated by transport trajectory modeling, potentially exerting broader impacts on the marine environment. By linking pollutant prioritization with transport trajectories and considering anthropogenic drivers, the present study provides a practical strategy for effectively controlling environmentally mobile pharmaceuticals in the urban river-estuary continuum. • Caffeine and paracetamol were predominant in the river-estuary continuum. • The rank of pharmaceutical residue followed: OTC > POM > Pharmacy only medicine. • Pharmacy and prescription drug residues were mainly from populations aged ≥45. • The top identified vPvM&PMT compounds were fluconazole, trimethoprim, and sitagliptin. • Transport trajectories in the river-estuary-sea system varied among the estuaries.
Luo et al. (Sun,) studied this question.