Distribution of heavy metals and persistent organic pollutants in sediment from coastal areas of northern and middle Viet Nam

Abstract

Heavy metals and persistent organic pollutants (POPs) in surface and core sediments can reflect the status and trend of pollution in the study area and help to assess negative impacts on the ecosystem. However, comprehensive studies dealing with multiple classes of inorganic and organic contaminants, such as toxic heavy metals and POPs, in sediment core samples in Vietnamese coastal areas have been relatively limited in recent years. In this study, the concentrations of heavy metals and several groups of POPs, including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), in surface and core sediment samples collected from estuarine areas in northern and central Vietnam were determined to evaluate their bioaccumulation characteristics in both special and temporal terms. The accumulation pattern of POPs in surface sediments in some estuaries along central coasts was in the order of PCBs > PBDEs > DDTs > HCHs. The concentrations of PCBs and PBDEs in surface sediments showed more obvious variations than did those of DDTs and HCHs. The residue concentrations of OCPs reached their highest values in the sediment layers corresponding to the late 1960s and early 1980s, and the peak concentrations of PCBs in the sediment layer occurred in the 1970s. The concentrations of total PBDEs, BDE-209, and several heavy metals, such as Cd, Cr, Cu, Pb, and Zn, in the core sediments of the Day River have tended to increase gradually in recent years. Our results of POP and metal accumulation in sediment core layers generally reflect the pattern of usage in Vietnam, such as the effect of the ban of OCPs and the recent input of emerging industrial chemical PBDEs into coastal areas.