WINTER TRANSPORT OF CHERNOBYL RADIONUCLIDES FROM A MONTANE CATCHMENT TO AN ICE-COVERED LAKE

The amounts of Cs-137 and Sr-90 have been determined in the inflows and outflows of the Norwegian sub-alpine lake, Ovre Heimdalsvatn, in March/April during the period of ice-cover, when discharge is extremely stable. The lake is situated in an area contaminated by Chernobyl fallout. The transported course particulate plant material has been collected in traps; the particles and colloids have been removed from water samples by cross-flow ultrafiltration. On the basis of radionuclide inputs and outputs, lake budget calculations have been made for Cs-137 and Sr-90 during the period of ice-cover. Daily transport of radionuclides is considerably less than that observed during the spring snowmelt period when discharges are high. Size distribution patterns of Cs and Sr observed during winter are compared with previously published data from the same lake during the spring spate. The retention of Cs-137 is similar in winter and spring, but retention of Sr-90 is greater in winter.