Historical record of polychlorinated biphenyls (PCBs) in the continental shelf of the Korea Strait

The vertical distribution of PCBs was measured in a dated core from the continental shelf of the Korea Strait. The historical trend of deposition and fluxes of individual and total PCB agreed well with the dynamics of historical tendencies of PCBs consumption in South Korea up to mid-1980 and a peak of total PCBs of 810 ng kg1 was recorded at the turn of the 1960s. A second period of deposition, when concentrations of total PCB up to 1007 ng kg1 were reached, was evidenced between 1989 and 2010 after the ban of PCBs. Sediments deposited in 1990se2010, and sediments deposited in the period of maximum PCBs use (1956e1983) are both enriched in the less chlorinated homologue groups (tri- and tetrachlorobyphenyls) and congener PCB 118. However, the ratio of dioxin-like PCBs, and dichloro- and hexachloro homologue groups disclosed compositional variations between the two time periods. Source analysis suggested that PCBs in the sediment record mainly originated from Kanechlor 300, Kanechlor 400 and Aroclor 1242 technical mixtures overlapped by secondary/unintentional combustion sources from regional steel making processes in the last decades (1990s-2010).