Post-Impact Assessment of Oil Pollution on Some Soil Characteristics in Ikot Abasi, Niger Delta Region, Nigeria

Abstract

Following a large-scale crude oil spillage in 2007, soil surveys were conducted in 2008 and in 2012 for post-impact assessment of the pollution on some soil characteristics in Ikot Abasi, Niger Delta Area, Nigeria. Soil characteristics examined include: pH, organic carbon (C), total nitrogen (N), available phosphorus (P), exchangeable cations (Ca, Mg, Na, K) exchangeable acidity (EA), effective cation exchange capacity (ECEC) base saturation (BS), total petroleum hydrocarbons (TPH), micronutrients (Fe, Mn, Zn, Cu) and heavy metals (Cadmium (Cd) and lead (Pb)). Soil analysis results in 2008 showed phenomenally greater values in some characteristics compared to 2012 results – five years after the pollution. In 2008, soil pH (6.8), organic (201.4 g/kg), N (5.65 g/kg), TPH, Pb, Fe, Mn, Zn, Cu, and Cd (3294.9, 2316.3, 23086.8, 189.4, 31.25, 29.1 and 4.22 mg/kg, respectively), were extremely (between 1.77 x 10⁵ and 1.2 x 10² percent) higher than the respective values in 2012. On the other hand, available P(6.8 mg/kg), Ca, Mg, Na, K, EA, ECEC (2.2, 1.1., 0.04, 0.08, 1.6, 5.0 cmol/kg, respectively) and BS (68.5%) in 2008 were relatively higher in 2012, indicating a suppressive effect of oil pollution on these characteristics. The results showed that oil pollution is accompanied by major soil nutrient imbalances and phenomenal increases in soil TPH and some heavy metals. However, the impact of the pollution diminishes with time. This has serious implications on agricultural productivity of the land, ground water pollution and health of the people. Also, remediation approach to adopt and payment of compensation should be based on the magnitude of the pollution and persistence of the impact of the pollution.

Keywords: Impact assessment, oil pollution, soil characteristics, Niger Delta, Nigeria.