Time-Lapse Geological Assessment of Groundwater and Soil; A Case Study of Oghara Farmlands, Delta State, Nigeria (Published)
The use of mineral fertilizers and nutrients is widely adopted in conventional agricultural practices, playing an essential role in maintaining optimal crop yields and improving overall quality. To aid farmers in effective fertilization and crop management strategies, non-invasive geophysical techniques can offer insights into the nutrient distribution within the soil. This study deemed it imperative to assess the physicochemical parameters and heavy metals (HM) present in the groundwater and soil of the study area. A total of three groundwater samples and five soil samples were collected and tested for different physical properties, such as pH, alkalinity, electrical conductivity (EC), temperature, total hardness (TH), total dissolved solids (TDS), total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl⁻), nitrate (NO₃⁻), sulfate (SO₄²⁻), phosphate (PO₂₄⁻), and ammoniacal nitrogen (NH₄–N). The heavy metals (HM) checked included iron (Fe), chromium (Cr), lead (Pb), copper (Cu), zinc (Zn), nickel (Ni), manganese (Mn), and cadmium (Cd). Recently, electrical resistivity tomography (ERT) has been used in local studies to measure changes in soil properties. Unfortunately, the signals we measure from the ground are mixed up because of changes in the soil both sideways and up and down, making it hard to figure out what each change is contributing. The analysis of groundwater and soil revealed that, with the exception of a few parameters, groundwater samples fell below the WHO permissible limit. The soil’s porosity, permeability, and the surrounding topography influence the migration rate. The rates of migration vary between the first and second locations. It has been found that if the vertical migration rate in the dry sand layer (which is about 13.7 meters thick based on drilling data) stays the same, the fertilizer contaminant will take about 0.5 years to reach the wet sandy layer below it in the first location, while in the second location, it will take around 1 year. Detailed calculations to determine the arrival time at the sandy layer has been conducted. Ultimately, it is imperative for the government to guarantee the installation of water purification plants during the process of borehole drilling, as this will help further decrease the existing salinity levels in the groundwater.
Keywords: Date, Fertilizer, Heavy Metal, Migration, pH, permissible