Occurrence and photochemical fate of perfluorochemicals in a tropical urban watershed

Abstract

The occurrence of perfluorochemicals (PFCs) was studied in rivers and canals feeding into Marina Reservoir, which collects water from Singapore’s largest and most urbanized watershed. A total of 19 PFCs were targeted and 16 compounds were detected. Contaminants were present under both wet and dry weather conditions, indicating that non-point sources contribute to the occurrence of these contaminants. Sediments collected from different places within the watershed contained PFCs that were not detected in water samples. A longitudinal profile along Alexandra Canal revealed the presence of a PFC point source. The annual input of PFCs into the reservoir was estimated to be 35 ± 12 kg/year based on the PFC depth profile in the reservoir, partitioning onto sedimentary material and input from the tributaries. Phototransformation kinetics of PFCs was studied under laboratory conditions. The bimolecular reaction rate constant of a model PFC contaminant (N-EtFOSE (N-ethyl perfluorooctane sulfonamidoethanol) with photochemically produced was determined using simulated sunlight irradiation and competitive kinetics.