ABSTRACT
Soil and water pollution pose significant environmental challenges in coastal regions worldwide, driven by population growth, urbanization, and industrialization. This study focuses on the Environmental Hydrogeochemistry of the Benin Formation in the Niger Delta, Nigeria, specifically the Port Harcourt, Aba, and Owerri axis. The study area encompasses latitudes 4°40’N to 5°40’N and longitudes 6°50’E to 7°50’E, covering approximately 12,056 km².
The investigation reveals that the aquifers in the region predominantly consist of unconfined sands with intercalations of gravels, clay, and shale. Geoelectric sections, borehole logs, and sieve analysis confirm the prevalence of sandy horizons in the area. Pumping tests indicate high transmissivity ranging from 152.0 m²/day to 2835.0 m²/day, with an average of 1026.0 m²/day, while specific capacity varies from 828.0 m³/day to 15314.0 m³/day, with an average of 6258.0 m³/day. The hydraulic conductivity ranges from 3.2 m/day to 478.4 m/day, with a mean of 98.6 m/day, suggesting a porous, permeable, and prolific groundwater aquifer.
The geochemical data exhibit wide ranges and high standard deviations, implying significant variations in groundwater quality within the study area. Based on the Piper, Durov, and Scholler diagrams, six hydrochemical facies were identified: Na-Cl, Ca-Mg-HCO3, Mg-Ca-SO4, Ca-Mg-Cl, Na-Fe-Cl, and Na-Fe-Cl-NO3. Additionally, heavy metal enrichment index revealed 12 elements in decreasing order: Fe > Ni > Cu > Zn > Mn > Cd > V > Co > Pb > Cr > As > Hg.
The study attributes soil and water deterioration in the area to salt intrusion, high iron content, acid rain, hydrocarbon pollution, agrochemical usage, industrial effluents, and poor sanitation. Saltwater/freshwater interface occurs between 5 m and 185 m, while iron-rich water is found between 20 m and 175 m, with the presence of marcasite, a sulfide mineral, at depths between 150 m and 180 m.
To address these issues, a modified DRASTIC model, called DRASTICA, was developed to construct an aquifer vulnerability map. The study recommends the establishment of modern sanitary landfills to replace existing open-dumpsites and emphasizes the urgency of eradicating gas flaring and minimizing oil spills in the area. Bioremediation and phytoremediation techniques are suggested for the cleanup of hydrocarbon-contaminated soils and water.
The study demonstrates the efficiency of multivariate statistical techniques in evaluating hydrogeochemical data, providing valuable insights for addressing soil and water pollution in the study area.
Assessing Environmental Hydrogeochemistry in the Benin Formation of the Niger Delta, Nigeria: A Study of the Port Harcourt, Aba, and Owerri Axis.