ABSTRACT
We studied the natural radioactivity distribution of an α-emitting radionuclide, 226Ra in water, sediment and biota (plankton, weed, snail, bivalve, prawn and fish) of Cauvery river ecosystem extending a stretch of 95 km. The dissolved 226Ra concentration in river water ranged from 0·82mBq.I-1 to l 06mBq.l-1 (mean: 0·93mBq.l-1) and the activity in river sediments from 4·7Bq.kg-1 to 6·9Bq.Kg-1 (mean: 5·6Bq.kgg-1 dry wt.). The 226Ra activity levels in the biota were within a narrow range from below detection limit to 3·80 Bq.kg-1 (wet wt). Generally higher 226Ra concentrations are observed in the shells and bones of aquatic organisms than in their tissues and muscles. The concentration factors (CFs) of 226Ra for the biotic components ranged from ~ 101 to ~ 103. The significance of 226Ra activity in the abiotic and biotic components of Cauvery river are discussed.