Cesium in perch in lakes from northern Sweden after Chernobyl

The aim of this project is to find measures to reduce the level of radioactive cesium in fish. 41 lakes in east central Sweden that received large amounts of cesium after the Chernobyl accident are studied. Most lakes have perch with cesium content for above the present maximum acceptable limit of 1500 Bq/kg wet weight. The median values for 1986 and 1987 were 3950 and 2650 Bq/kg respectively. The possibilities for speeding up the natural decrease of cesium 137 by liming (to counteract the acidification) and adding nutrient (N and P, to increase bioproduction and 'dilute' the cesium contents) are analyzed. 4-7000 lakes in Sweden are supposed to have fish with cesium levels above 1500 Bq/kg. A preliminary recovery prognosis is given. (12 p. English summary) (L.E.)