Assessing the Impact of Chlorpyrifos on Soil Health: Microbial and Physicochemical Changes in Pristine Soils

Chlorpyrifos (CP), a common organophosphate pesticide, has serious ecological concerns, especially in pristine forest soils. This study examined how chlorpyrifos affected indigenous microbial communities and physicochemical qualities of Toru-Ebeni Forest soils in Bayelsa State, Nigeria. Soil samples from three sites were tested for chlorpyrifos concentrations: low (2.19 µg/gdw), medium (5.2 µg/gdw), and high (6.7 µg/gdw). Concentration-dependent effects on microbial growth and pesticide breakdown were observed over 22 days. The control group had significantly higher total heterotrophic bacterial counts (2.0 x 10³ to 1.18 x 10¹⁰ CFU/gdw) than the low, medium, and high concentrations, indicating chlorpyrifos inhibits microbial growth. Staphylococcus (19.5%), Pseudomonas (10.9%), and Bacillus (7.2%) dominated. Chlorpyrifos degradation was 80.7%, resulting in a residue reduction from 5.2 µg/gdw on Day 1 to 1.0 µg/gdw on Day 22. Significant reductions in nitrogen (25.4 ± 0.2 mg/kg to 19.0 ± 0.1 mg/kg) and phosphorus (5.8 ± 0.1 mg/kg to 4.1 ± 0.1 mg/kg) concentrations were observed. Heavy metals including Cu, Pb, Cd, and Zn declined. Changes in urease and dehydrogenase activity indicated soil microbial disturbance. This study emphasises the significance of microbial communities in chlorpyrifos biodegradation and the possibility for tropical soil bioremediation to address pesticide contamination