Assessment of radionuclides in the soil of residential areas of the Chittagong metropolitan city, Bangladesh and evaluation of associated radiological risk

Soil samples from the three residential hubs of Chittagong city, Bangladesh were analyzed using gamma spectrometry to estimate radiation hazard due to natural radioactive sources and anthropogenic nuclide Cs-137. The activity concentration of Ra-226 was found to be in the range 11-25 Bq.kg(-1), Th-232 in the range 38-59 Bq.kg(-1) and K-40 in the range 246-414 Bq.kg(-1). These results were used to calculate the radiological hazard parameters including Excess of Lifetime Cancer Risk (ELCR). The estimated outdoor gamma exposure rates were 40.6-63.8 nGy.h(-1). The radiation hazard index (radium equivalent activity) ranged from 90-140 Bq.kg(-1). The average value of the ELCR was found to be 0.21 x 10(-3), which is lower than the world average. Sporadic fallout of Cs-137 was observed with an average value of 2.0 Bq.kg(-1).