The historical residue trend of PCBs in the Agassiz Ice Cap, Ellesmere Island, Canada

Current detailed measurements of contaminant deposition cannot provide a historical perspective except through long-term monitoring programs. In the Aretic, ice caps provide an alternative to lake sediments, in that the annual snow layers reflect atmospheric deposition. As a result of the remoteness of the ice cap and the limited summer melt, annual layers undergo little chemical change, especially after the first summer season, and therefore provide a well-defined historical record. Initial work was undertaken at the Agassiz Ice Cap (80°49′50″ N, 72°56′30″ W) beginning in 1986, but a major effort was undertaken in 1993, during which snow samples covering 30 years were taken from a snow pit. Large volume snow samples were obtained for the determination of PCB congeners. Mean ΣPCB deposition to the ice cap ranged from 930 ng/m²/year in the winter of 1967-1968 to a minimum of 91 ng/m²/year in 1980-1981. Since 1980-1981, deposition has again increased to a local maximum of 848 ng/m²/year (in 1989-1990). The mean deposition for the 30 years of record was 406 ng/m²/year, with no evidence of a consistent long-term trend.