Radium is naturally occurring radioactive element in the earth's crust. It is chemically
similar to calcium and absorbed from soil by plants, passed up the food chain to humans.
The occurrence and the distribution of radioactivity in water depend on the local geological
characteristics of the source, soil, rock and other factors that control the occurrence and
distribution of radionuclides in ground water and the hydro geological condition and the
geochemistry of radionuclides. Activities of the naturally occurring radionuclides 226Ra and
222Rn were determined in natural ground water of the Mandya district, Karnataka State,
India. The concentration of 222Rn in borewell water varies form 6.44 ± 0.20 to
44.83 ± 0.54 Bq l1 with geometric mean 16.42 ± 0.31 Bq l1. Higher radon concentrations
were observed at Yettaganahalli and Mandya city. 226Ra concentration varies form
14.26 ± 0.32 to 81.06 ± 0.99 mBq l1 with geometric mean 27.61 ± 0.43 mBq l1. It is observed
that the radon concentration is high in ground water around the granitic rock exposures
and similarly observation of high values of radon is reported in sheared gneiss which
covers major portion of the Mandya district to phyllites and schists. The total dose due to
ingestion and inhalation varies from 26.31 to 178.53 mSv y1 with a geometric mean of
65.94 mSv y1, which is below the prescribed dose limit of 100 mSv y1 by WHO.
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