AIRBORNE POLLUTION IN 5 DRAINAGE BASINS IN EASTERN FINNMARK, NORWAY -AN EVALUATION OF OVERBANK SEDIMENTS AS SAMPLING MEDIUM FOR ENVIRONMENTAL-STUDIES AND GEOCHEMICAL MAPPING

To study whether airborne pollution can be detected in overbank sedime nts, samples collected from five overbank sediment profiles in eastern Finnmark, Norway, at 1 cm depth intervals, were subjected to chemical analysis and Pb-210 dating. The studied drainage basins constitute pa rts of an area polluted by emissions from two Ni-Cu smelters in Russia . In the most polluted catchment area, the surface sample showed a 5-f old higher Ni concentration and a 3-fold higher Cu concentration than the pre-industrial sediments at depth. The increases started at the sa me time as the smelters. Slight Ni increases were also detected in the neighbouring drainage basin, while no significant concentration chang e was seen in drainage basins previously shown to be only weakly influ enced by the smelter emissions. In the most polluted drainage basin. t he increase in Ni accumulation rate did not equal the airborne deposit ion rate. Selective surface erosion of fine grained particles with adh ering airborne Ni has probably caused excess Ni accumulation in both o verbank and lake sediments, On the contrary, opening of minerogenic po int sources may dilute the pollutant concentrations in the drainage se diments. Thus, dating of the sediment profiles is necessary to determi ne the airborne pollutant accumulation rates. However, dating is not n ecessary to map the resultant concentration increase, that may show th e increased exposure of humans and biota in contact with the sediments .