Organophosphate esters in reservoir water from a metropolitan city in the Guangdong-Hong Kong-Macao Greater Bay Area, China, and their ecological risk

Organophosphate esters (OPEs) are emerging flame retardants widely used in products such as furniture, electronic equipment, construction, and plastics. It has been demonstrated that OPEs are harmful to humans and aquatic organisms, thus posing a threat to ecosystems. Considering that reservoirs are critical sources of drinking water for residents in Southern China, this study quantified nine OPEs in water samples collected from 29 reservoirs and their tributaries. The temporal and spatial distributions of OPEs were analyzed and their ecological risks were assessed. The results showed an extensive presence of OPEs in reservoirs, and the median concentration of Σ₉OPEs was much higher in the dry season (65.3 ng/L) than in the wet season (21.3 ng/L). Triisobutyl phosphate (TiBP) (median: 5.24 ng/L) and tris(2-ethylhexyl) phosphate (TEHP) (median: 10.8 ng/L) dominated in the wet and dry seasons, respectively. Other OPEs varied considerably in concentrations over time, related to their physical and chemical properties, environmental factors (e.g., precipitation and temperature), and varied applications. Furthermore, the significant correlations of individual OPEs suggest their shared utilization, emission sources, and environmental behaviors. Spatially, there was no significant difference (P > 0.05) among the Σ₉OPEs concentrations in water samples from different sites (inlet, reservoir, outlet, and tributary) of the reservoirs. Additionally, the concentrations of OPEs in reservoir water samples could be linked to industrial development, economic conditions, and population density. OPEs in the reservoir pose low ecological risks (RQ < 0.1), except for EDHPP and TEHP, which present median ecological risks (RQ = 0.54 and 0.38, respectively). Future studies could investigate more OPEs and their joint effects with other organic pollutants, as well as survey the chemical reactions and degradation pathways of OPEs in different environmental matrices to assess their potential ecotoxicity more comprehensively.