Spatiotemporal variations and risk assessment of organophosphate esters in surface waters of the Eastern Route of the South-to-North Water Diversion Project, China: A comprehensive survey for human health

Water contamination by organophosphate esters (OPEs) is a worldwide issue. Yet, there has been little investigation into the residue of OPEs in artificial water environments. Thus, 140 surface water samples from the Eastern Route (ER) of the South-to-North Water Diversion Project (SNWDP), the world’s longest water transfer project, were collected and tested for 12 OPEs to conduct a comprehensive ecological and health risk assessment. The total OPE (ΣOPE) concentration was 28.3-906.3 and 80.9-478.1 ng L -1 in the constructed waterways and four regulative lakes. The mean ΣOPE concentration did not vary by season in the Lunan Canal, but it changed seasonally in the Subei Canal, due to the Lunan Canal inputs under artificial canal regulation. Spatial distribution indicated that the conveyor manufacturing activity may be a critical source for OPEs in the Lunan Canal. Among four lakes, Nansi Lake (273.6 ng L -1 ) showed the highest mean ΣOPE concentration, which may be related to the relatively high local industrial wastewater emissions. The OPE concentration and composition were changed seasonally in Dongping Lake under the influence of the ER-SNWDP. Tris(2-choroethyl) phosphate (TCEP) would produce moderate risks to algae in 87.5% and 94.4% of water sites from Nansi Lake and Lunan Canal, which warrants further attention. Children exposed to the targeted OPEs were at greater health risks than adults from water consumption. Even in the high exposure scenario, the carcinogenic risks of the target OPEs to children and adults were all within acceptable levels. Overall, surface waters from the ER-SNWDP were safe for drinking. • OPE concentrations in constructed waterways were influenced by canal regulation • OPE concentrations in lakes were related to local industrial wastewater emissions • Conveyor manufacturing activity may be an important source for OPEs in the canal • Ecological risks of TCEP to algae and fish deserve more attention in the future • Children were at greater health and carcinogenic risks than adults by water intake