Distributions and seasonal variations of organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers in surface sediment from coastal areas of central Vietnam

Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in surface sediment from five estuaries of central coasts of Vietnam to understand the spatial distributions and seasonal variations. The contamination pattern was in the order: PCBs (9.72–3730 ng g−1 dry wt.) > PBDEs (11.8–311 ng g−1 dry wt.) > DDTs (0.462–26.7 ng g−1 dry wt.) > HCHs (0.491–22.6 ng g−1 dry wt.) > endosulfan compounds (0.196–19.4 ng g−1 dry wt.). DDTs and HCHs showed a little geographical variation, whereas PCBs and PBDEs exhibited clearer spatial distribution trend. Elevated concentrations of PCBs and PBDEs were detected in some sites in Nghe An and Quang Binh Province, which could be related to the human activities such as tourism, transportation, and domestic consumption. Seasonal variations of DDTs and HCHs were observed, showing higher residues in rainy seasons.