Base line radioactivity levels in Kaiga site soil and its migration to biosphere

The effects of variation in different parameters on the environmental distribution of base line 137Cs and 40K activities in Kaiga environment and their migration into biosphere are discussed. Transfer factors of these radionuclides from soil to different parts of commonly available plants in this region were estimated. Base line radioactivity levels in soil at Kaiga were higher as compared to pre-operational values reported from other power station sites in India and were mainly attributed to the very high precipitation rate prevailing in this area. Also, this area being an undisturbed forest land, fallout activities are re-circulated to the soil by the decay of parts of trees. 40K and 137Cs activity levels in leaves of shallow rooted plants were found to be higher as compared to that in deep rooted trees. Transfer factors of soil to plant parts revealed that there is no major bio-accumulation of 137Cs in any parts of Colocassia esculenta (L.) and Chromolaena odorata (L.) King and Robinson. Comparison of 40K/137Cs ratio between soil and different parts of these plants has revealed that uptake of K is relatively more efficient as compared to that of Cs, presumably because of the faster kinetics of K due to its larger atom inventory in the soil. (author)