Occurrence and ecological risk assessment of organophosphate esters in surface water from rivers and lakes in urban Hanoi, Vietnam

In this study, an investigation on the pollution status, distribution, and ecological risk to the aquatic organisms of six organophosphate tri-esters (tri-OPEs) and two organophosphate tri-esters (di-OPEs) in surface water in urban Hanoi, Vietnam were conducted. In 37 surveyed water samples (6 rivers and 17 lakes), all eight targeted OPEs were discovered with a detection frequency (DF) of 41-100% and the concentration varied largely from below the method detection limit (<MDL) to 6138 ng L-1. The total concentrations of six tri-OPEs (Sigma(6)tri-OPEs) were 46-3644 ng L-1 (average 1409 ng L-1) and the total concentrations of two di-OPEs (Sigma(2)di-OPEs) ranged from 2.6 to 6138 ng L-1 (average 351 ng L-1). In general, the Sigma(6)tri-OPEs in water samples collected in rivers (average 2262 ng L-1) were higher than those in lakes (average 1000 ng L-1). The most dominant chemical was tris(2-chloro-1-methyl ethyl) phosphate (TCPP) with a DF of 100% and took up 75% (on average) of Sigma(6)tri-OPEs. Principal component analysis showed that most of the tri- and di-OPEs in lakes may come from similar emission sources. While, there were at least four different origins of organophosphate esters (OPEs) in rivers in urban Hanoi. The risk quotient (RQ) was estimated for the detected concentration of tri- and di-OPEs in water samples and the toxicological relevant concentration for three trophic groups of algae, crustaceans, and fish. The RQs and the total of RQs for each group were lower than 1, indicating that the effects of each OPE and their OPEs' combined effects on the aquatic environment in Hanoi were at low to medium levels.