A one year study of the seasonal variations of sDDT and PCB levels in fish from heated and unheated areas near a nuclear power plant

An investigation of the influence of excess heat discharge from a nuclear power plant on the residual levels of the sDOT and PCB in roach and perch has been made during a period of one year. A seasonal variation of the residual concentrations was observed, with the highest levels during spring and early summer and lower more stable levels in the autumn. Significantly higher levels of the sDDT and PCB was observed in perch from the cooling water recipient as compared to values in perch from the intake area. No significant differences could however be verified for roach. The result stress the importance that, in a monitoring program, a sampling period with stable ecological conditions is selected.