Environmental risk assessment of background radiation, natural radioactivity and toxic elements in rocks and soils of Nkalagu quarry, Southeastern Nigeria
Merrious Oviri Ofomola, Fredrick Oghenebrorie Ugbede, Ochuko Anomohanran
Abstract
This study investigated the environmental risk of natural radioactivity and some toxic elements in quarry site located in Nkalagu, Southeastern Nigeria. Background radiometric, natural radioactivity and selected toxic elements in quarry rocks and soil samples were analyzed for the environmental risk assessment of the quarry area. In-situ background radiation survey of the quarry environment indicated radiation exposure levels ranging from 0.012 to 0.017 mRh–1 with a total average of 0.015 mRh–1, which exceeded the recommended ambient level but not to a statistically significant rate. Mean activity concentrations of 232Th, 226Ra and 40K in quarry rocks exceeded those of the soil, meanwhile 232Th and 226Ra concentrations in both samples were higher than world average. Results of radiological hazard indices in quarry rocks were higher than the permissible limits, except for the lifetime cancer risk. The mean concentration of the analyzed toxic elements in the rock and soil followed the order; Fe > Zn > Cr > Pb > Cd and Fe > Zn > Pb > Cr > Cd respectively. The analyzed metal concentrations were within WHO permissible limit for soil samples. Findings from the study showed that the background radiation of the quarry environment is slightly elevated which may result to higher exposure dose of workers. The quarry rocks may pose radiological risks when used as building construction material, whereas that of the soil pose no influence on health and it is classified as unpolluted with low environmental and ecological risks. Conclusively, it is advised that the use of the quarry rocks be excluded from building construction, especially in the interior in order to limit the exposure of the population.