The vertical distribution of PCBs was measured in a datedcore from the profundal sediments of Esthwaite Water,U.K. The resulting historical record of
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PCB depositionagreedwell with published U.K. production data. Ratiosbetweenthe various PCB homolog groups revealed significantcompositional variations with depth. Sedimentsdepositedin the last ~10 years and sediments deposited before PCBproduction began are both relatively enriched in the lesschlorinated homolog groups. When considered withotheravailable data, these enrichments provide evidence forpost-depositional mobility of PCBs favoring the more aqueoussoluble and volatile compounds. The results lendfurthersupport to a growing body of evidence that recyling ofPCBs is occurring between the sediments and overlyingwaters, associated with solubilization and diffusivetransport.