RADON CONCENTRATIONS IN THE PYRAMID OF THE SUN AT TEOTIHUACAN

Measurements of radon were taken inside the Pyramid of the Sun at the pre-Columbian Teotihuacan site in Mexico. Beneath the Pyramid of the S un, there is a prehispanic tunnel that was used for ritual ceremonies. We evaluated the radon levels inside this and other tunnels plus tunn els excavated for research purposes by archaeologists. Passive nuclear track detectors were used to measure radon. Measurements were made in winter during the dry season because the tunnels flood in the rainy s eason. Radon ranged from 70 to 190 Bq m(-3). The radon levels decrease d with height above ground level which probably reflects relatively ea sy escape routes for radon through the loosely stacked volcanic stores in the outer wall covering.