318 E . Srinivasa et al .: Radioprotection 2024 , 59 ( 4 ), 317 – 326
Fig . 1 . Geological and lithological map of Hassan district , Karnataka state , India .
primordial radionuclides in the soil samples and to estimate the radiological hazards .
1.1 Geology of the study area
The Hassan district lies between 12 ° 13 0 and 13 ° 33 0 north latitude and 75 ° 33 0 and 76 ° 38 0 east longitude . The geological map of the study area as shown in Figure 1 . Geologically , Hassan district forms a part of Precambrian terrain . The major litho units are granitic gneiss , granulites , granites , associated pegmatite rocks and metamorphic rocks , steatite , Dharwarian schists and dyke rocks . The most important rock formation of the district is Nuggehalli and Holenarasipura Schist belt . These two schist belts are the host of number of mineral deposits like Chromites , Titaniferous magnetite , Chalcopyrite , Kaolin , Asbestos , Quartz , Granites , Gabbroid , Ultramafic igneous rocks , Dolerites , Diorites , Bauxite , magnesite , green granites ( Dykes ), Garnets , micas , Kyanite , columbite and tantalite etc . The important types of soil observed in the Hassan district are red sandy soil , red silty-clayey soil , mixed soil and black soil ( Srinivasa et al ., 2015 , 2019 ).
2 Materials and methods
2.1 Collection and preparation of soil samples
The soil samples were collected from 40 randomly selected undisturbed locations in the Hassan district and its surrounding areas to determine the activity concentration of natural radionuclides in the soil using standard procedures
( Srinivasa et al ., 2019 ; Volchok and de Planque , 1983 ). The samples were dried with sunlight to remove the moisture and then powdered and sieved through 125 mm size mesh . The samples were poured into porcelain dish and then dried in an oven at 110 ° C for the overnight . The samples were then poured into plastic container of 250 ml capacity . The containers were firmly sealed internally and externally using proper adhesive tapes and weighed . The samples were kept for at least 30 days to attain secular equilibrium between parent and daughters of uranium and thorium series ( Srinivasa et al ., 2019 ; Srilatha et al ., 2015 ).
2.2 Estimation of 238 U , 226 Ra , 232 Th , and 40 K in soil samples
The activity concentration of 238 U , 226 Ra , 232 Th , and 40 Kin soil samples was determined by gamma ray spectrometry employing an n-type low background HPGe detector using GENIE-2000 spectrum analysis software at the laboratory of the University Science Instrumentation Centre , Mangalore University , for the present study . HPGe n-type detector having 48 % efficiency coupled to 16 K MCA was used . It was enclosed by lead shield of thickness 10 cm ( model GR 4021 , Canberra , USA ). Using area under the photo peaks of 214 Pb ( 351.9 keV ) to estimate 238 U , 214 Bi ( 609.3 , 1129.3 and 1764.5 keV ) to estimate 226 Ra , one photo peak of 228 Ac ( 911.2 KeV ) and two photo peaks of 208 Tl ( 583.1 and 2614.5 KeV ) to estimate 232 Th , and ( 1460.8 keV ) to estimate 40 K activity concentrations respectively . The standard procedure was followed to calibrate the instrument . Compton