RADON CONCENTRATION LEVELS IN GROUND-WATER FROM TOLUCA, MEXICO

Concentration levels of Rn-222 have been analysed in water samples from deep wells of the aquifers around the City of Toluca, Mexico. The Rn-222 source is the decay of Ra-226 within the solid matrix of the aquifer. With a half life of 1600 years the Ra-226 continuously releases Rn-222 to the pores, from which it diffuses into the main body of water. This paper describes the methods used for sampling and measuring solubilized and Ra-226-supported Rn-222 in the water samples, in order to evaluate possible health hazards due to the presence of radon in the drinking water supplies. The relationship of Rn-222 with the hydrogeologic characteristics of the zone is also described. The analytical method involves laboratory extraction of Rn-222 into toluene. Alpha disintegrations of Rn-222 and contributions from short-lived daughters are counted by the liquid scintillation technique. The system was calibrated using a Ra-222 standard solution. Results up to 11.3 Bq/l of Rn-222 were obtained in the water samples.