Organophosphate flame retardants in leachates from six municipal landfills across China

With the phasing out of brominated flame retardants, organophosphate flame retardants (OPFRs) have been widely used and further detected in multiple environmental media. However, municipal landfill leachates, an important source of contamination of OPFRs to aquatic environment, have not been fully understood, especially in a developing country like China. Thus, the occurrence, aqueous removal efficiency, environmental emission, and risk assessment of 10 OPFRs were investigated in leachates from six municipal landfills across China. The results indicated that except triethyl phosphate (TEP), the remaining 9 OPFRs were detected in both raw and final leachates with different frequencies higher than 33.3%. The range of total concentrations of OPFRs (ΣOPFRs) across China was 29.0-437 and 0.652-32.4 μg L^-1 in raw and final leachates, respectively. Tris(2-chloroethyl) phosphate (TCEP) was the dominant species and accounted for 78.5% and 85.8% of average ΣOPFR concentration in raw and final leachates, respectively. This may be because TCEP is the most prevalently used OPFR in China. The overall aqueous removal efficiency of ΣOPFRs across China ranged from 57.7% to 99.8%. Tris(2-butoxyethyl) phosphate was the most removed species (98.8%), whereas TCEP was the least removed species (91.5%). The annual emissions of ΣOPFRs discharged into the aquatic environment from municipal landfills across China were estimated to be between 170 and 7094 g. Further risk assessment based on risk quotient values in the final leachates showed that most OPFRs posed negligible risk except TCEP (medium and high risk) and tributyl phosphate (medium risk).