Community-level ecological risks of organophosphate esters in surface waters from the northern Liaodong Bay, China: A comparative analysis of multiple species sensitivity distributions

Abstract

Organophosphate esters (OPEs), as preferred substitutes for brominated flame retardants, pervaded the global aquatic environment and have been proven to exert multiple toxicological effects on organisms. However, significant information gaps remain about the community-level risks of OPEs to aquatic ecosystems. This study adopted 10 species sensitivity distribution (SSD) parametric models coupled with the acute-to-chronic conversion of toxicity data to perform comprehensive evaluations on the single and joint community-level ecological risks of OPEs in surface waters from the northern Liaodong Bay, China. OPEs were widely detected across all monitoring sites, with the total concentrations ranging from 47.6 to 303 ng/L. The toxicity dataset of triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), triisobutyl phosphate (TiBP), tris(2-carboxyethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(1, 3-dichloro-2-propyl) phosphate (TDCIPP) met the basic data requirements of SSD fitting. Model-dependent variations in the hazard concentrations corresponding to the 5% cumulative probability (HC₅s) reached up to two orders of magnitude for a certain OPE homolog. Weibull, Logistic, Weibull, Sigmoid, Logistic, and Gumbel were ultimately preferred as the best-fitting models for TEP, TnBP, TiBP, TCEP, TCPP, and TDCIPP, with their HC₅s being 3.67 mg/L, 0.125 mg/L, 1.54 mg/L, 1.30 mg/L, 1.89 mg/L, and 0.0751 mg/L, respectively. The risk quotients of OPE homologs and the hazard indexes of OPEs were all <<0.1, indicating low risks. This study could provide a scientific methodological framework for effectively establishing environmental quality benchmarks and assessing ecological risks for emerging contaminants.