Polychlorinated biphenyls in the global ocean

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Polychlorinated biphenyls (PCBs) are a group of industrial chemicals that were manufactured through the 1970s, at which point they were banned due to concerns about their adverse effects on humans and the environment, their enrichment in top predators, persistence, and long-range transport. The presence of PCBs in remote and marine environments was recognized early. A landmark transocean study in the late 1980s implied the global contamination of the oceans by PCBs, and the importance of atmospheric deposition. Several decades later, there is general consensus that the PCB concentrations are greater in the Northern Hemisphere oceans. Concentrations of individual PCBs are typically at or below 1 pg L- 1 in the surface waters of the oceans. Greater concentrations are recorded for the marginal seas, in particular the Mediterranean and Baltic. Little is known about profiles of PCBs in the open ocean water column, though the advent of passive sampling has made it possible to measure them more easily. Recent results seem to imply subsurface maxima for PCBs in the North Atlantic Ocean. Major progress has been made in understanding the presence and profiles of PCBs in the oceans by linking their transport into and within the marine waters to biogeochemical processes. In particular, the coupling of PCB dynamics to the biological pump has furthered the understanding of why PCBs continue to be taken up in productive ocean regions, but not in the oligotrophic gyres. A mass budget for PCBs has been established for shelf sediments, but is still missing for the water column and deep sea sediments.

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World Seas: An Environmental Evaluation Volume III: Ecological Issues and Environmental Impacts