DEPOSITIONAL TIME TRENDS AND REMOBILIZATION OF PCBS IN LAKE-SEDIMENTS

The vertical distribution of PCBs was measured in a dated core from th e profundal sediments of Esthwaite Water, U.K. The resulting historica l record of Sigma PCB deposition agreed well with published U.K. produ ction data. Ratios between the various PCB homolog groups revealed sig nificant compositional variations with depth. Sediments deposited in t he last similar to 10 years and sediments deposited before PCB product ion began are both relatively enriched in the less chlorinated homolog groups. When considered with other available data, these enrichments provide evidence for post-depositional mobility of PCBs favoring the m ore aqueous soluble and volatile compounds. The results lend further s upport to a growing body of evidence that recyling of PCBs is occurrin g between the sediments and overlying waters, associated with solubili zation and diffusive transport.