Assessment of natural radionuclides in a fertilized farmland in Abeokuta, Nigeria: Implications for environmental radioactivity evaluation and monitoring

In this study, the concentrations of radionuclides were determined for soil samples obtained from a fertilized farm soils in Abeokuta, southwestern Nigeria. On the average, seven soil samples were obtained and keptin a sealed polythene bags. Then later dried and pulverized. Two hundred grams of each of the pulverized samples was held in a standard plastic container and left for about thirty days to allow for secular equilibrium between radium and its progenies. Radionuclides activity concentrations within the collected samples were measured using a calibrated NaI-based gamma- ray spectrometer. The detected natural radioactivity of soil samples are presented and radiological attributes for effective radiological hazards detection and monitoringfor the study location are equally estimated.The results revealed that the specific activity for K-40 radionuclides at location L7 is higher than the world average concentration of 420 Bq/kg. This is not unconnected to the fertilizer within that portion of the farm. However, the estimated radiological attributes in the farmland are relatively lower that the threshold standards, which implies that the soils in the farmland are free of any radiation hazards and pose no threat to farmers and the residents of that area. It is however recommended that organic manure should be used in the farmland rather than fertilizer and routine check on environmental radioactivity of the farmland should be done regularly for adequate monitoring

Ground radiometric survey for assessment of environmental radioactivity in a fertilized farmland: a case history in southwestern Nigeria

Soils in their natural state contain radionuclides and heavy metals at different concentrations which may be increased by the use of fertilizers. When the concentrations of radionuclides and in soils are higher in value than the recommended limits, this may pose health concern. In this study, absorbed dose rate was measured in-situ at thirty-five station points in the farmland using a caesium Iodide-based GammaRAE II R full range dosimeter held at gonald height above the surface.Results of the in-situ absorbed dose rate in air are presented and the potential risks to the farmers and near-by residents are equally assessed.The results revealed that the measured absorbed dose rate (ADRA) in the farm is high which is likely to be connected to the use of fertilizer in the farmland. It is highly recommended that the management of the farm should reduce the use of fertilizer but rather use natural organic manure that is less toxic. Also, a routine check on environmental radioactivity of the farmland should be done regularly for adequate monitoring

Radiogenic Components of Limestone Samples Collected from Ewekoro SW Nigeria: Implications for Public Radiological Health Risks Assessment and Monitoring

AIM: This research presents the radiogenic components in thirteen limestone samples from a quarry site in Ewekoro, southwestern Nigeria. METHODS: The distributions of natural radionuclides (238U, 232Th and 40K) in the limestone samples were determined by gamma spectroscopy using a well-type thallium-doped sodium iodide detector. Also, estimated associated radiological hazards are presented and compared with the standard threshold values. RESULTS: The activity concentrations for 238U, 232Th and 40K radionuclides range 18.09 ± 3.43-239.50 ± 25.74 Bqkg-1, 8.33 ± 0.83 - 360.01 ± 21.33 Bqkg-1 and 11.28 ± 0.81-735.26 ± 0.95 Bqkg-1 respectively. The radium equivalent activity concentration in the samples ranges 58.857-758.832 Bqkg-1 with samples S3, S4 and S11 values higher than the threshold limit of 370 Bqkg-1. Estimated dose rate and annual effective dose rate (AEDE) from the samples have ranges 28.754-330.917 nGyh-1 and 35.26-405.84 μSvy−1 respectively greater than the standard limit of 59 nGyh-1 and 70 μSvy−1 respectively for all samples except S9. The estimated external and internal indices are ranging 0.16 – 2.05 and 0.21 – 2.68 respectively, greater than permissible unity in some limestone samples such as S3, S4, S8, S11 and S13. Excess lifetime cancer risk was also computed using a life expectancy of 54.5 years. The results of higher radiological parameters in the limestone samples revealed that the miners have a high probability of contracting induced cancer. CONCLUSION: A regular check-up is recommended for the miners and staffs within the quarry site. Also, the residents within the environs should be relocated far away from the quarry site, as the particulates from the limestone rock blasting could contaminate the air in the study area

Evaluating the groundwater potential of coastal aquifer using geoelectrical resistivity survey and porosity estimation: A case in Ota, SW Nigeria

Geoelectrical resistivity sounding surveys was carried out at two locations (A and B) in the new CanaanCity residential estate of Canaan land Ota, Ogun state in order to locate possible targets for groundwater explorations. A total of twelve (12) vertical electrical soundings were conducted using the Schlumberger array configuration. The interpretations of the VES curves revealed five to six geoelectrical layers at location A which comprises VES1-7. The geoelectric units consist of the topsoil, sandy clay, lateritic clay, confining bed (clayey sand), and main aquifer (sand). The top of the aquifer in this part of the study area is between 40 m and 83.5 m. Likewise, a total of five to seven layers of geoelectrical units were delineated at the location B portion of the study site (VES 8–12) similar to location A with an addition of the shale unit that was interpreted to be that of the Akimbo Formation of the Dahomey Basin. The depth to the top of the productive aquifer within location B is in the range of 40–112.4 m. The delineated basal shale layer is impermeable, serving as the base seal rock for the confined aquifer system. The estimated porosity values range from 28% to 74%, indicating that the highly porous aquifer system in the area is the coastal plain sands mixed with the alluvium sand of the Benin Formation of Dahomey Basin. The study revealed the complexity of the productive aquifer system in the area and its undulating topography

Investigating the near surface leachate movement in an open dumpsite using surficial ERT method

Geoelectrical resistivity imaging technique was conducted at Abule-egba open dumpsite, Lagos with intentions to monitor the movement of the contaminant leachate within the near surface. The two survey traverses (T1 and T2) of 2D electrical resistivity tomography were conducted using Wenner array configuration with minimum electrode spacing of 1 metre and maximum data levels of seven. The inversion models revealed the two delineated geoelectrical layers which are sandy-clay and sand units. The leachate fluids has the resistivity values of 5.75 – 10.4 Ωm at depth range of 2.5 – 4.0 metres along T1 and T2 moving from NW to the SE section. The leachate fluids are capable of polluting shallow groundwater aquifer within the study area and the residents are advised to drill deeper in the subsurface for clean and portable groundwater resources. Keywords: Environmental Geophysics, Leachates, Near-surface geophysics, Open dumpsite, Electrical resistivity tomography (ERT