Radium content in ground water from a granitic batholith of the metamorphic basement, eastern São Paulo State, Brazil.

The radon emanation method was applied to measure the activity of 226Ra, dissolved and associated with suspended solids, in the ground waters from two wells drilled in the Morungaba Batholith fractured granites, intruded in the metamorphic basement, eastern border of the Paraná basin in São Paulo State, Brazil. The water samples were collected from March 2003,to April 2004, with a time interval of about one month between sampling campaigns. The mean observed dissolved 226Ra activity concentrations in the two wells were 47.9 +/- 7.1 and 51.6 +/- 8.8 mBq/L. No systematic time dependence of the 226Ra activity concentration was clearly identified. The activity of 226Ra associated with suspended solids contained in 1L of ground water fell, during the sampling period, from 13 +/- 1 to 0.8 +/- 0.1 mBq in one well and from 4.9 +/- 0.3 to 0.6 +/- 0.1 mBq in the second well.