Sub-Soil Properties of Hydrocarbon Contaminated Sites in Parts of the Eastern Niger Delta, Nigeria
American Research Journal of Earth Science
This study aims at assessing the subsurface soil properties of contaminated sites in parts of the Niger Delta with a view to providing basic data that would guide not only future development and construction in the region but in choosing remediation options for contaminated sites. Standard soil sampling and analytical methods were employed in the study. Soil moisture content values range from 5.2 to 97. 9 with spikes at Okrika OKR-CTRL and BM-CTRL probably due to shallow water table encountered
... at shallow depth of 2.0 m. While the average moisture level at contaminated sites was 20.08 while that of the control sites was 17. 85. The variation also suggests higher water retention potential of contaminated soils against normal clean soil which in essence will enhance contaminant persistence in the soil. The soil pH value for control sites tends to normal range i.e towards 7.0, while the values for impacted sites are slightly lower. Most samples had normal soil pH ranges except BM-SS1 which indicated acidic soil conditions with ranges of 4.5-5.8. Liquid Limit is higher for control samples than contaminated sites at Okrika, Ogu-Bolo, Bomu manifold and Norkpo while Liquid Limit value for impacted site at Sime is higher than the control site and similar for Nonwa sites. This variation could be as a result of the impact of the contamination on the soil. The plastic limit is highest at BM-SS, OGB-SSOKR-SSNOR-SS and lowest at SIM-CTRL, NOW-CTRL, NOW-SS, OGB-CTRL and BM-CTRL. Generally hydrocarbon contamination decreases liquid limit, plastic limit and Plasticity index of the soil. There is a generally slight reduction in porosity values at the impacted sites as compared with the control sites. The soil profile across the study area grade from fine silty sands to fine gravel sand and the soil profile up to depth of investigation were generally dominated by silts, sands and sandy clay in different proportions. Following this, stoppage of infiltration of liquid hydrocarbon product and movement of contaminated water through it will continue unhindered.