PCBs in Central Vietnam coastal lagoons: levels and trends in dynamic environments

PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008\ud in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to\ud evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained\ud with low total PCB concentrations (0.367–44.7 lg kg1). Atmospheric transport and post depositional\ud processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance\ud of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial\ud samples also suggests the presence of a unique source over the entire study area, probably\ud connected to mobilisation and long range transports from land-based stocks. The removal of consistent\ud sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological\ud events (such as typhoons) are suspected to be responsible for these sediment losses