Geophysical and hydro physicochemical investigation and pollution potential evaluation of an urban landfill in southern Nigeria

The study was conducted in an old landfill in the Calabar South local government area of Cross River State. The essence of the research work is to investigate groundwater quality within the area and evaluate the level of environmental pollution due to radioelement exposure to landfill waste. Ten profile (traverse) lines were created for the survey, and twenty vertical electrical soundings were probed with a maximum half-current electrode (AB/2) of 200 m. The result revealed four to five geoelectric layers. The rock strata and soil layers with a resistivity of less than 15 Ωm were interpreted as zones of contamination. Also, samples of groundwater were collected from four boreholes and six hand-dug wells for water quality and physicochemical analysis. The analysis shows that iron (Fe), total dissolved solids, Sulfate ( \(SO_{4}\) $S{O}_4$ ) and turbidity exceeded the recommended thresholds for drinking water. Consequently, the water quality index result showed that 2% of the samples produced good water, 1% produced water of poor quality, 20% of the samples produced very poor water, and 50% produced water unsuitable for human consumption. Subsequently, a radiation spectrometer was deployed to measure the radioelement concentration to determine the radio hazard and environmental pollution status of the area. Measurements of radiation due to man-made sources were undertaken in the ten profiles. The mean concentration and mean specific activity were determined for all the survey lines. While the mean concentration of \({}^{40}K\) ${}^{40}K$ and radiation dose rate were recorded below UNSCEAR’s (2000) proposed limits. \({}^{238}U\) ${}^{238}U$ and \({}^{232}Th\) ${}^{232}Th$ exceeded the recommended threshold for profiles seven to ten. The annual effective dose equivalent (AEDE) in the area was also calculated to be \(40.98\,\mu \,{\text{Sv/year}}\) $40.98\mu \text{Sv/year}$ . The research provides a multi-geophysical approach to evaluating and understanding hydro-geophysical and geo-environmental conditions related to landfill contamination.