RÉSUMÉ

The model slowly flowing media contained the native silt from the 30-km zone of the Chemobyl Nuclear Power Plant (NPP). There were compared the intensities of washing out Cs-137 from the media where Limnodrilus hoffmeisteri and Chironomus plumosus were introduced. At 12-18°C, one gram of oligochaetes effects in 0.46 Bq and the same mass of chironomids affords 1.24 Bq of Cs-137 released into the water during 24 hours. Using the removal coefficient proposed by the authors, it was calculated that more than 5% of Cs-137 contained in the water of the Kiev Reservoir might be determined by vital activities of oligochaetes and more than 1% of that - by chironomid larvae.