Post-Remediation Soil Recovery in K-Dere, Ogoniland: Implications for Sustainable Environmental Restoration
Lebari Sibe *
Biochemistry/Chemistry Technology, School of Science Laboratory Technology, University of Port Harcourt, Choba, Rivers State, P.M.B. 5323, Nigeria.
Bapakaye Ibisiki
Kenule Beeson Saro-Wiwa Polytechnic, Bori, Rivers State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
This study investigated the post-remediation effects on soil health in K-Dere, Ogoniland, Rivers State, to determine whether remediation activities have effectively restored soil physicochemical and biological functionality in a hydrocarbon-impacted environment. Composite soil samples were collected from remediated soil (RS) and unremediated soil (URS) at a depth of 0–15 cm, and laboratory analyses were conducted in triplicate using standard soil analytical methods to assess microbial biomass, enzyme activities, organic matter status, nutrient composition and key physicochemical properties. The results showed that total organic carbon decreased from 2.10% in URS to 0.55% in RS (74.0% reduction), whereas total organic nitrogen increased from 0.20% to 0.40% (100% increase). Sulphate concentration increased from 56.98 to 66.30 mg/kg (16.4% increase), nitrate from 4.6 to 10.7 mg/kg (132.6% increase), and phosphate from 5.88 to 23.4 mg/kg (298.0% increase). Bulk density declined from 7.59 to 5.24 g/cm³ (31.0% reduction), water retention capacity increased from 0.375 to 0.433 (15.5% increase), and cation exchange capacity rose from 5.1 to 18.5 cmol/kg (262.7% increase). In contrast, biological indicators declined markedly, as bacterial counts decreased from 4.0 × 10⁶ to 3.9 × 10⁵ cfu/g (90.3% reduction), fungal counts from 2.6 × 10⁶ to 3.0 × 10⁵ cfu/g (88.5% reduction), and dehydrogenase, urease and phosphatase activities decreased by 73.1%, 74.6% and 70.0%, respectively. The overall soil health measured by the Soil Quality Index (SQI) indicated better soil quality in the unremediated soil (SQI = 0.79 > 0.70) than in the remediated soil (SQI = 0.64 < 0.70). The study concludes that remediation activities in K-Dere have substantially improved soil nutrient availability and physicochemical conditions but have not yet achieved full biological recovery. It is therefore recommended that future remediation programmes integrate biological enhancement strategies, including organic amendments and microbial stimulation, supported by long-term post-remediation monitoring to ensure sustainable restoration of soil health.
Keywords: Soil, remediation, physicochemical, soil quality index, microbial biomass, soil health