CHERNOBYL-DERIVED RADIOCESIUM IN FISH AS DEPENDENT ON WATER-QUALITY AND LAKE MORPHOMETRY

Cs-137 concentrations in perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus obtained from lakes of different size and water quality in an area which received about 10-67 kBq m(-2) Cs-137, were compared with environmental data. Radiocaesium concentrations were hig hest in pike, and were about two to three times higher in the pike and perch than in the roach. The largest perch had about four times more Cs-137 than the smallest ones, but the activities in the pike and roac h were independent of fish size. All of the water quality parameters e xamined correlated with Cs-137 concentrations in the fish, but the con centrations of Cs-137 in the bottom sediment did not. Cs-137 fallout a nd water retention time in lakes showed a positive correlation with fi sh Cs-137, while the size of the catchment area, phosphorus content of the water, water colour, pH and electrical conductivity showed a nega tive one. Thus there was more Cs-137 in the fish from the oligotrophic lakes than from the eutrophic ones, from the less humic lakes than fr om the more humic ones, from the more acid than from the less acid one s and from the lakes containing less potassium than from those contain ing more potassium. The depth, area and volume of the lake did not aff ect radiocaesium in the fish. Regression equations are presented for p redicting Cs-137 in fish on the basis of environmental data. Fallout, total phosphorus and pH together had the highest influence in multiple regression models but were less significant in the roach than in the perch and pike.