Distribution of 228Ra and 226Ra in the high background radiation areas of South India

The 228Ra and 226Ra activity in soil samples from four regions of natural high background radiation areas (NHBRA) in the country (Chavara, Neendakara in Kerala, Manavalakurichi-Kudiraimozhi in Tamil Nadu and Bhimilipatnam in Andhra Pradesh) are reported. The 228Ra and 226Ra activity varied widely at different sites and the mean values at the core deposit areas are 2612 Bq.kg-1 and 242 Bq.kg-1 respectively. The corresponding levels at inland areas spread over 10 km radial distance from the core deposits locations except at Manavalakurichi are 170 Bq.kg-1 and 20 Bq.kg-1. At the Manavalakurichi area, the inland soil samples indicated higher activity levels comparable to the mineral deposits regions. The average gamma absorbed dose rate in air is estimated to be 1740 nGy.h-l at the deposits region and 115 nGy.h-l at the environmental areas. Significant radium concentrations are also observed in the sediment samples collected from the lakes and rivers available at the study areas. (author)