MEASUREMENTS OF ACTIVITY CONCENTRATIONS OF NATURALLY OCCURRING RADIONUCLIDES IN SOIL SAMPLES FROM PUNJAB PROVINCE OF PAKISTAN AND ASSESSMENT OF RADIOLOGICAL HAZARDS

摘要

The natural level of radioactivity in soil is one of the major causes of external gamma rays exposure. It was considered imperative to measure gamma-ray activity concentrations due to naturally occurring, potentially hazardous radionuclides from ~(232)Th, ~(226)Ra and ~(40)K in soil samples from Punjab, the most populated province of Pakistan. The activity concentrations were measured in soil samples collected from all 34 district headquarters of Punjab province using a P-type coaxial high purity germanium (HPGe)-based gamma-ray spectrometer having a relative efficiency of 60%. The mean activity concentrations for ~(232)Th, ~(226)Ra and ~(40)K were found to be 41 ± 8, 35 ± 7 and 615 ± 143 Bq kg~(-1), respectively in soil samples from all 34 district headquarters of Punjab. The mean values of radium equivalent index (Ra_(eq)) and total annual external gamma radiation dose were found to be 141 ± 27 Bq kg~(-1) and 0.38 mSv, respectively. Since these estimated radiological impact assessment factors are lower than the recommended values there seems to be no potential radiological health hazard associated with the soils from the district headquarters in the Punjab province of Pakistan. Geological studies show that most of the soils in Punjab have developed on the extensive fluviatile deposits of five rivers and a stable ratio of natural activity concentrations is observed in soil samples of the areas under study.