Abstract: Taking Beibu Gulf, South China Sea as a case, the occurrence, source, and ecological risks of 12 organophosphate esters (OPEs) were investigated in 34 surface sediment samples. The Σ12OPEs in the sediments ranged from <LOQ to 35.1 ng·g^-1. Triphenyl phosphate (TPHP), tri-n-butyl phosphate (TNBP), tris (2-chloro-propyl) phosphate (TCIPP) and tris (2-chloroethyl) phosphate (TCEP) were the dominant OPEs in the surface sediments. Generally, the total mass fraction of OPEs detected in sediments from the offshore was higher than that in the near shore, and the mass fraction for major OPEs were also different between the above two areas. On the one hand, the main reason might be related to their physiochemical properties. TPHP and TNBP compounds with higher lipophilicity might be more likely to accumulate in the sediments. On the other hand, it might be related to the source. For example, the OPEs detected in the offshore might be related to the oil exploitation and transportation, submarine optical cable and oil pipeline laying, shipping activities and the transportation of circulation in Beibu Gulf, while the discharge of life and industrial sewage as well as marine aquaculture might be the major sources for OPEs detected in the inshore area. Risk assessment revealed that most individual OPE could pose low ecological risks, but medium ecological risks of TPHP and the mixture of OPEs on aquatic organisms were found, which requires more attention. Therefore, the OPEs pollution situation in Beibu Gulf needs to be paid attention to, especially the pollution emission and control TCIPP and TCEP from inshore area, as well as TPHP and TNBP from offshore area, so as to reduce OPEs pollution from the source.

Key words: organophosphate esters (OPEs), sediment, Beibu Gulf, occurrence, ecological risk