The Concentration Of Natural Radionuclides In Soil Samples From The Practical Year Agricultural Farmland, University Of Ibadan
A total of 48 soil samples from the University of Ibadan practical year farmland were collected and analyzed using gamma ray spectrometer in order to determine the activity concentrations of the natural radionuclides. From the activity concentrations determined, the radium equivalent activity, the external hazard index, the internal hazard index, the absorbed dose rate and the effective dose rate in the soil were evaluated. The activity concentrations and hazard indices values were less than the accepted world average values. Keywords Concentration, Gamma Exposure, Hazard Indices, Natural Radionuclides, Soil Sediments Radionuclides are found in natural surroundings, mostly in the air, soil and water. Radionuclide means type of atom that exhibits radioactivity. Each radionuclide is characterized by its own half life, which is the time required for half of the radioactive substance to undergo spontaneous decay. It is the nucleus of atom that exhibits the properties of spontaneous disintegration. Radionuclides can be used to calculate the age of rocks and minerals using radiometric dating method. Naturally occurring radioactivity is common in the rocks and minerals as well as the soil that make up the planet. Also, they exist in the homes, building materials and so on The concentration of the 235 U, 232 Th, and 40 K were varied depending on soil type, the mineral content, geological features and geological conditions. (1) (2).These can severely affect the distribution of radionuclides in soil. Types of rocks also dictate the higher radionuclide present in it. Higher radionuclide level are mostly found in igneous rocks, such as granite and lower levels commonly with the sedimentary rocks (3).The concentration of thorium and uranium in high background radiation dose rate areas is as a result of soil developed from igneous rocks (4) Natural radioactivity is widespread in the earth environment and it exists in various geological formations such as earth crust, rocks, soils, plants, water and air (5) Soil radionuclide activity concentration is one of the main determinants of the natural occurring radiation. When rocks are disintegrated through natural process, radionuclides are carried to soil by rain infiltration process (6) In addition to natural sources, soil radioactivity is also affected by man made activities. Naturally occurring radionuclides (uranium and thorium series, etc. are the largest contributors to radiation doses received by human beings. Furthermore, the knowledge of the radionuclide content of soils is central to the establishment of environmental baselines for various substrates and environments (7) Although, Farming is one of the most crucial means of survival in Nigeria back in the early centuries and it is still a prominent way of sustenance till date. Planting of crops is essential since human beings and some animals depend on plants and crops to survive. The soil where this cropping is done may be as a result of sediments of rocks or rocks that are broken down through weathering processes and transported by erosion. The mineral contents that make up the soil may have some naturally occurring radionuclides and may as well give the details about the type of rocks that comprises of the soil. To understand the pathways by which radionuclides reach humans requires an assessment of those soil properties that affect the abundance and distribution of radionuclides. In addition, continuous farming and application of fertilizers are seen to increase the distribution of radionuclides in the farm. Therefore, this research is carried out to evaluate and to analyze the concentration of natural radionuclides and the gamma exposure levels in soils from the University of Ibadan agricultural farm. The concentrations of natural radionuclides in the farm soil and their distribution across the farm will be determined and if the continuous farming has had any effect on the concentration of these radionuclides which may increase exposure levels in the area of the farm. The aim of this study is to evaluate and analyze the distribution of the concentration of natural radionuclides and the gamma exposure levels in soils from the University of Ibadan agricultural farm. To achieve this aim, the following are the objectives of the research: To determine the activity concentration of 40 K, 226 Ra and 232 Th in the soil samples.