Impact of Crude Oil Spillage on the Physico-Chemical Characteristics of Soils in Izombe, Imo State, Southeast, Nigeria.

Abstract The study investigated the impact of crude oil spillage on the soil physico-chemical properties in Izombe, Imo State, in 2024. A free survey technique was used in the field sampling in which two profile pits were dug; one at the polluted site (Umuokwu) and the other at the unpolluted site (Ugbele). Routine soil analysis was conducted on some physico-chemical properties as well as heavy metals. Statistical comparisons and permissible limit assessments were adopted to determine environmental and agricultural implications. Results showed that soil texture though an inherent property was significantly altered, with polluted site showing higher clay content (44.6%) and lower sand content (46.4%), compared to 24.35% clay and 62.15% sand in the unpolluted site, affecting aeration and root penetration. Bulk density (1.19g/cm3) was significantly higher in the polluted site than in the unpolluted site (0.95 g/cm3). Similarly, total porosity was significantly lower in the polluted soils (58.67%) compared to the unpolluted site (64.13%). Moisture content was higher in the polluted site (13.81%) than the unpolluted site (11.2%). Perhaps due to higher clay retention and high bulk density which inhibited drainage. Soil pH in the polluted soil (6.13) was slightly higher than in the unpolluted site (5.86) indicating minimal impact on nutrient solubility. Exchangeable cations were significantly depleted in the polluted soils, with potassium (K) at 0.26 Cmol/kg and 0.57Cmol/kg unpolluted; Sodium (Na) at 0.22 Cmol/kg compared to 0.31 Cmol/kg, reflecting increased leaching and soil degradation. Effective Cation Exchange Capacity (ECEC) was lower in the polluted soils (4.53 Cmol/kg) than in the unpolluted site (5.3 Cmol/kg) below the 6 Cmol/kg threshold, indicating low nutrient retention capacity. Heavy metal concentrations in both the polluted and unpolluted soils were shown to be below permissible limits Chromium (Cr) had a mean value of 1.25 mg/kg (polluted), 0.46 mg/kg (unpolluted) while Cadmium (Cd) 1.08 mg/kg (polluted) and 0.70 mg/kg (unpolluted); Copper (Cu) 1.18 mg/kg (polluted), 0.61 mg/kg (unpolluted); Zinc (Zn) 1.14 mg/kg (polluted) and 0.39 mg/kg (polluted). The decline in soil fertility and reduced cation retention poses a long-term risk to agricultural productivity. Bioremediation is recommended as a sustainable solution, involving compost, introduction of hydrocarbon-degrading microorganisms, poultry manure etc. to accelerate hydrocarbon breakdown and restore soil structure.