Radioactive pollution in freshwater ecosystems from Macedonia, Greece

The levels of radioactive contamination by artificial radiocesium (Cs-137, Cs-134) as well as the concentrations of natural radioisotopes (K-40, Ra-226, Ra-228, Th-228) in sediments and aquatic plants were evaluated in selected aquatic biotopes in Macedonia, Greece. Radionuclide analysis was performed in Marinelli beakers by a gamma spectrometry system with an Hp-Ge detector of 20% relative efficiency. Cs-137 concentration activities are higher in sediment than in plant material; in general, roots showed greater Cs-137 concentration than leaves, while stems showed the lowest concentration. Cs-137 is significantly higher at 95% confidence level in the river Axios than in the rivers Strymon and Aliakmon. Leaves, especially young ones, show K-40 activities higher than roots or stems. From the studied watersystems, the river Axios and Prespa Lake are more contaminated from Cs-137 and Cs-134. K-40 activity is significantly higher at the 95% confidence level in the river Axios than in the rivers Aliakmon and Pinios. The K-40 activity is also high, especially in Prespa Lake. High activities of Ra-226, Ra-228, Th-228, and K-40 were found in Polyphytos Lake, presumably as a result of the operation of the coal power plants in this area