Natural environmental radioactivity and estimation of radiation exposure from saline soils

Abstract

The study was conducted for the investigation of amount of radioactivity in the barren and cultivated soil of Bio saline Research Station in Pakka Anna, established by Nuclear Institute for Agriculture and Biology (NIAB) in 1990, 34 km. away from the city of Faisalabad, in the Punjab province of Pakistan. The studies were done on an area of about 100 hectares of two types of virgin and fertilized saline soils. The technique of gamma ray spectrometry was applied using HPGe (high purity germanium) gamma ray detector and a PC based MCA. Activity concentration levels due to 40 K, 137 Cs, 226 Ra and 232 Th were measured in 250 saline soil samples collected at a spacing of about 4 hectares at the depth level of 0–25 cm. with a step of 5 cm. depth. Activity concentrations ranges of the concerned radionuclides for both of the soils were as follows: 40 K, for virgin and cultivated saline soil was 500−610.2 and Bq/kg 560.2−635.6 respectively; 137 Cs, 3.57−3.63 and 1.98−5.15 Bq/kg 238 U, 26.3−31.6 and 30.3−38.7 Bq/kg, and 232 Th, 50.6−55.3 and 50.6−64.0 Bq/kg respectively. The absorbed dose rate in air lies in the region 63-73 nGyh -1 and 68-83 nGyh -1 for virgin and fertilized soils respectively. This indicates that this region lies in the area of higher radiation background, while comparing with the worlds’ average. The slightly higher value of dose in the fertilized farm may be due to the use of fertilizers for cultivation. Before the radiometric measurements, chemical analysis for concentration of Na, Ca and Mg was also carried out along with the measurement of electrical conductivity and pH of the soil samples.