[Pollution Characteristics and Risk Assessment of Typical Organophosphate Esters in Beijing Municipal Wastewater Treatment Plant and the Receiving Water]

Organophosphate esters (OPEs) are ubiquitous in the environment and pose a potential threat to ecosystems and human health. A method for the determination of eight OPEs by ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) was established. The recovery rates of eight target compounds with different solid-phase extraction columns, different eluents, and different eluent volumes were compared. The results showed that using ENVI-18 column enrichment, OPEs were eluted with 8 mL acetonitrile containing 25% (volume fraction) dichloromethane, and the labeled recovery rate of the target compound was 92.5%-102.2%. The recoveries of different matrix samples were 88.5%-116.1% and relative standard deviation was 1.7%-9.9%. The concentration range of 8 different detectable organophosphate esters in the effluent of sewage treatment plant is 85.9-235.4 ng·L^-1 during the six-day sampling process, permissive river downstream of the six-day ΣOPEs average total concentration was 130.3 ng·L^-1, higher than the 119.4 ng·L^-1 upstream water concentration, but lower than the sewage treatment plant effluent concentration of total 162.5ng·L^-1. The study shows that the sewage treatment plant cannot completely remove OPEs; for triethyl phosphate (TEP) and 3 (2-ethyl hexyl) phosphate ester (TEHP) there exists a negative removal phenomenon, whereas for other OPEs the removal rate was between 14.1% and 84.9%, and the total ΣOPEs removal rate by the sewage plant was 50.0%. The TPhP in the effluent of the sewage treatment plant has medium environmental risk (RQ>0.1), and other organophosphates have low environmental risk (RQ<0.1); however, the long-term mixing effects of organophosphate esters on the ecosystem of the receiving river should not be ignored.