Occurrence, spatial distributions, sources, and potential risks of organophosphate esters in Yarlung Tsangpo River and its main tributaries on the Tibetan Plateau.

Organophosphate esters (OPEs) are extensively utilized as flame retardants and plasticizers in a wide range of products. Because of their high solubility, mobility, and persistence, OPEs are frequently detected in aquatic environments with relatively high concentrations and may pose risks to the ecosystem and human health. In the present study, the occurrence, spatial distributions, influencing factors, sources, and potential risks of eight OPE congeners in the Yarlung Tsangpo River and its main tributaries (the Lhasa, Nianchu, and Niyang Rivers) in the summer were investigated. Although all of the OPE congeners were detected, the detection frequencies of the individual OPEs varied from 10.3 % (TPeP) to 100 % (TPPO). The concentrations of the ∑OPEs ranged from 15.1 to 2.55 × 10 ng/L while those of the individual OPEs ranged from below the method detection limit to 2.51 × 10 ng/L, with TPPO, TCEP, and TCPP being the main congeners. In all the four rivers, sampling sites near to the more populated regions had higher ∑OPE concentrations than those farther away. The Lhasa River also presented higher ∑OPE concentrations than the Niyang River. Local anthropogenic activities, wastewater treatment plants, and hydrological features such as temperature, pH, and salinity might be the main factors influencing OPE distribution. Source appointment of the OPEs indicated that the three halogenated OPEs might share similar sources, whereas the sources of TPPO might be more complex. The ecological and health risks of the OPEs in the rivers were at acceptable levels. However, TPPO at YJ17 and LS08 would pose a moderate ecological risk to the aquatic organisms, indicating that more attention should be paid to it at these sites.