Post-Remediation Soil Quality Dynamics: The Role of Indigenous Bio-Resource Materials in Regulating pH in Petroleum Hydrocarbon-Impacted Soils

Abstract

Petroleum hydrocarbon contamination remains a persistent environmental challenge in oil-producing regions, particularly in the Niger Delta of Nigeria, where soil quality and ecosystem functionality have been severely compromised. In this study, an indigenous bioresource-based solid biostimulant was developed and evaluated for the remediation of petroleum-contaminated soils. The biostimulant, formulated from locally sourced organic materials, was applied to soils with varying Total Petroleum Hydrocarbon (TPH) concentrations (7,346 to 14,518 mg/kg), and remediation performance was monitored over a three-week period using soil pH as a key indicator of recovery. Results showed a consistent, time-dependent increase in soil pH across all treatment systems, reflecting progressive restoration of soil chemical balance. The magnitude of pH change increased with contamination level, ranging from 1.40 to 3.89% at the lowest TPH and 17.60 to 21.79% at the highest. Strong linear relationships between pH change and time (R² = 0.804 to 0.968, p ≤ 0.05) confirmed the reliability of the remediation process. Optimal performance was observed at moderate to high contamination levels (10,520 to 12,553 mg/kg), where both efficiency and predictability were highest. At the highest contamination level, although pH improvement was greatest, reduced linearity suggested possible system stress due to excessive hydrocarbon load. The findings demonstrate that the bioresource-based biostimulant effectively enhanced and accelerated hydrocarbon degradation, leading to measurable soil recovery. This approach offers a sustainable, low-cost alternative to conventional remediation technologies and holds significant potential for large-scale application in petroleum-impacted environments. Further field validation and process optimization are recommended to support its adoption and commercialization.