[Spatiotemporal Occurrence of Organophosphate Esters in the Surface Water and Sediment of Taihu Lake and Relevant Risk Assessment].

ABSTRACT

Aiming to explore the spatiotemporal occurrence of organophosphate esters (OPEs) in the aquatic environment of Taihu Lake and to assess the relevant ecological risk, monomeric and oligomeric OPEs in the surface water and sediment of Taihu Lake were determined using solid phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry. The target monomeric OPEs included chlorinated OPEs, alkyl OPEs, and aryl OPEs. There was no significant difference in the spatial distribution of OPEs in water and sediment between the pollutant-impacted and less-impacted zones. The average concentrations of OPEs in summer and winter were, respectively, 752.7 and 498.5 ng·L-1 in water and 124.0 and 54.5 ng·g-1 in sediment, indicating an obvious seasonal difference, especially for the monomeric OPEs. The OPEs levels in both the water and sediment were ranked in the order of chlorinated OPEs > alkyl OPEs > aryl OPEs≈oligomeric OPEs. The pseudo-partitioning coefficients (Kd) of OPEs between the sediment and surface water of Taihu Lake were much higher in summer (0.05-4.17 L·g-1) compared to those in winter (0.02-3.47 L·g-1) and were significantly positively correlated with the lg Kow values of OPEs. Based on the median concentrations of OPEs in the water of Taihu Lake, the ecological risk of OPEs was assessed by risk quotient (RQ) values, which indicated a medium risk at an RQ level of 0.34 during winter and 0.35 during summer. The assessment results showed that the risk ranking of OPEs was consistent with that of their concentrations, and the monomeric OPEs posed a higher ecological risk in summer compared to that in winter. Although the ecological risk of oligomeric OPEs in this study was not serious and was lower than that of monomeric OPEs, it is an urgent requirement to conduct ecotoxicology studies on oligomeric OPEs in the future since available data is highly limited at present.