Occurrence of Halogenated Flame Retardants in Sediment off an Urbanized Coastal Zone: Association with Urbanization and Industrialization

To examine the impacts of urbanization and industrialization on the coastal environment, sediment samples were collected from an urbanized coastal zone (i.e., Daya Bay and Hong Kong waters of South China) and analyzed for 20 polybrominated diphenyl ethers (PBDEs) and 10 alternative halogenated flame retardants (AHFRs). The sum concentration of PBDEs was in the range of 1.7-55 (mean: 17) ng g^-1, suggesting a moderate pollution level compared to the global range. The higher fractions of AHFRs (i.e., TBB+TBPH, BTBPE and DBDPE) than those of legacy PBDEs (i.e., penta-BDE, octa-BDE and deca-BDE) corresponded with the phasing out of PBDEs and increasing demand for AHFRs. Heavy contamination occurred at the estuary of Dan'ao River flowing through the Daya Bay Economic Zone, home to a variety of petrochemicals and electronics manufacturing facilities. The concentrations of HFRs in surface sediments of Hong Kong were the highest in Victoria Harbor, which receives around 1.4 million tons of primarily treated sewage daily, and a good relationship (r² = 0.80; p < 0.0001) between the HFR concentration and population density in each council district was observed, highlighting the effect of urbanization. Moreover, the AHFR concentrations were significantly correlated (r² > 0.73; p < 0.05) with the production volume of electronic devices, production value of electronic industries and population size, demonstrating the importance of industrializing and urbanizing processes in dictating the historical input patterns of AHFRs.