Natural radioactivity levels in the soils and human risk assessment in Tiruchirappalli district (Tamil Nadu, India)

The activity concentrations of Ra-226, Th-232 and K-40 in 91 soil samples collected from proposed housing sites in Tiruchirappalli district were measured using gamma ray spectrometer, Rn-222 activity using SSNTD technique and ambient absorbed gamma dose employing hand held scintillometer. The mean activity concentrations of Ra-226, Th-232 and 40 K were found to be 6.5, 61.7 and 379.8 Bq kg(-1), respectively. The mean ambient gamma dose rate was 66.7 nGy h(-1) and the mean radon activity 210.8 Bq m(-3). The study identified two stations in which Ra-eq levels exceeded the permissible limit (370 Bq kg(-1)).