Indexing low-level radioisotopes in Felda Jengka cultivated land / Masitah Alias

Naturally occurring radionuclides such as 40K, 226Ra and 228Ra which emit gamma radiation through their decay process could reach the human in vicinity. The amount of radioactivity concentration of these radionuclides is the important factor in assessing whether it harmful or vice versa. In this study, the oil palm plantation in Jengka 15, Maran District, Pahang Darul Makmur was chosen as a study area, since geographically it has various sections such as slope, flat land and catchments area. The samples were collected using hand auger at specific locations determined by using global positioning system. The surface dose measurement were done in-situ using dose rate meter, and the radioactivity concentration levels were done by counting the soil samples using gamma spectrometer with HPGe detector in the laboratory. The concentrations of uranium, thorium and potassium were determined using neutron activation analysis technique. It is found that the mean radioactivity concentrations for 40K are 70.7 ± 12.4 Bq/kg and 55.5 ± 10.9 Bq/kg, 50.5 ± 11.2 Bq/kg and 61.9 ± 12.8 Bq/kg, and 243.0 ± 29 Bq/kg for flats 1 and 2, slopes 1 and 2 and catchments area respectively. The mean radioactivity concentrations for 226Ra are 16.6 ± 0.8 Bq/kg and 17.9 ± 0.8 Bq/kg, 20.1 ± 1.4 Bq/kg and 18.8 ± 1.7 Bq/kg and 22.1 ± 1.1 Bq/kg for flats 1 and 2, slopes 1 and 2 and catchments area respectively. The mean radioactivity concentrations for 228Ra are 22.4 ± 2.5 Bq/kg and 26.9 ± 2.6 Bq/kg, 27.1 ± 3.5 Bq/kg and 24.5 ± 3.1 Bq/kg, and 36.6 ± 13.2 Bg/kg for flats 1 and 2, slopes 1 and 2 and catchments respectively. The mean concentrations of uranium are 3.0 ± 0.2 µg/g and 2.0 ± 0.2 µg/g for flats area, 2.0 ± 0.2 µg/g for slopes area and 3.1 ± 0.2 µg/g for catchments area. The mean concentrations of thorium are 7.7 ± 3 µg/g and 6.9 ± 2 µg/g for flats area, 3.9 ± 1µg/g and 4.3 ± 2 µg/g for slopes area, and 11.4 ± 4 µg/g for catchments area. The mean concentrations of potassium are 1763 ± 14 µg/g and 2148 ± 13 µg/g for flats area, 1484 ± 13 µg/g and 1657 ± 15 µg/g for slopes area, and 6200 ± 13 µg/g for catchments area.