IJOART. Keywords: Mechanical remediation; Impacted Soil; Reassessment; Gas chromatography; Hydrocarbon; Gokana

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1 International Journal of Advancements in Research & Technology, Volume 6, Issue 2, February Possible Persistence of Crude Oil in Remediated Sites in Gokana, Ogoni. 1 Okorondu, J. N., 1 Osuji, Leo. C., 2 Ofodile, S. E., 1 Onojake, M.C. 1 Department of Pure and Industrial Chemistry, University of Port Harcourt, Rivers State, Nigeria, 2 Rivers State University of Science and Technology, Port Harcourt, Rivers State, Nigeria justin.okorondu@gmail.com ABSTRACT The concept of potential trapping of patches of oil in permeable soils necessitated a revisit to a previously remediated oil impacted sites in Gokana. Incident of oil spillage by vandalisation of oil pipelines has been recorded in the area in which mechanical remediation was used for the cleanup. The objective of this study is to carry out a reassessment of the impacted sites using the results from a Gas Chromatographic (GC) fingerprint. Soil samples of varying depth (0-15 cm and cm depth) were collected from two previously impacted sites in Gokana. Hydrocarbon analysis was carried out on the samples using a GC-FID for the aliphatic hydrocarbons and GC-MS for polycyclic aromatic hydrocarbons; results show TPH concentrations increases with soil depth in the range of 1, mg/kg to 1, and 2, mg/kg to 3, mg/kg for the two sites respectively. Also, the lighter polycyclic aromatic hydrocarbon compounds (PAHs) were more abundant on the subsurface (15 30 cm) than the surface soil (0 15 cm) whiles the heavier polycyclic aromatic hydrocarbons also increases with soil depth. Other aromatic compounds such as (Anthracene, Fluoranthene, and Pyrene) did not show any significant difference. The implication of hydrocarbon in the soil after remediation insinuates that, the hydrocarbon content of the soil at sites 1(BH1) and site 2 (BH2) for both surface and subsurface soils were all higher than the threshold value instituted by EGASPIN, which is mg/kg. This infers that the remediation exercise was not performed to a satisfactory limit. The study divulges the possibility of potential trapping of patches of oil in permeable soils even after remediation. Keywords: Mechanical remediation; Impacted Soil; Reassessment; Gas chromatography; Hydrocarbon; Gokana 1.0 Introduction: Evaporation can cause about 40% loss of the volume of light Hydrocarbon pollution of soil can occur in many ways, from natural seepage of hydrocarbons in areas where petroleum is found in shallow reservoirs, to unintended spillage of crude oil on the ground. Regardless of the source of contamination, once hydrocarbons come into contact with the soil, they modify its physical and chemical properties. The degree of modification depends on the soil type, the specific composition of the hydrocarbon spilled and the quantity spilled [11]. When a spill occurs, the oil in the environment is exposed to weathering; this entails evaporation, dissolution, dispersion, medium crudes [14]. Remediation processes constitute various methods applied to alleviate or reduce the impact of the oil spill on the environment and the inhabitants, which include fauna and flora and human beings. The method varies from application of booms, use of skimmers, use of dispersants, high and low pressure pumps and array of mechanical methods. One of the most commonly applied is heavy equipment for the removal oily sediment and soil [1]. The method also generates a lot of waste. One of the limitation of this method as heighted in the photochemical oxidation, water-oil emulsification, and Exxon Valdez spill is that patches of oil were trapped in microbial degradation, adsorption onto suspended particulate materials, sinking and sedimentation [12], [10]. In short term, after heterogeneous low permeability sediment overlaid by high permeability sediment [1]. The implication is that sites where oil spill, evaporation is the single most important and dominant such methods were employed or which bear such weathering process that can cause considerable changes in the chemical composition and physical properties of the spilled oil. characteristics of soil permeability should frequently be revisited for assessment of potential hydrocarbon trapped by low permeability soil overlaid by high permeability soils.

2 International Journal of Advancements in Research & Technology, Volume 6, Issue 2, February In this study, a reassessment of previously mechanically remediated sites was performed. Soil samples were obtained at different depths in the soil and subjected to GC-FID and GC- MS analysis for TPH and PAH respectively. were determined using Agilent 7820 GC with 5975 MSD in Total Ion Count (TIC) mode with Helium as the carrier gas. 3.0 Description of study area with a Google map: 2.0 Materials and method. Sample collection Soil samples were collected randomly from previously remediated site in Gokana, Ogoni; samples were obtained using soil auger, which enables collection of representative soil samples at specific depths. Samples were obtained at 0-15 cm and cm respectively and collected in Teflon lined glass bottle, properly labeled, stored in ice chest before transport to the laboratory. Sample Preparation Ten grams (10 g) of the soil sample was blended with 10g of anhydrous sodium sulphate and extracted in a soxhlet apparatus for 4 hours using dichloromethane (DCM). This was later filtered and concentrated to a volume of 2 ml in a rotary evaporator. The sample clean up and fractionation was done in Fig. 1. Map of the study area a fractionating column using activated silica gel of 100 mesh B-dere is a community in Gokana Local Government area, size topped with 0.5 g anhydrous sodium sulphate. Sample Analysis Ogoni-Nigeria. It plays host to a lot of oil companies in the Niger Delta. Over the years, there has been incidence of oil spillage especially from pipeline vandalism in the area. The site 1 µl of the soil extract was injected into the GC through an auto-sampler. The total petroleum hydrocarbons, TPH was used for this study had already undergone mechanical remediation in the past years. determined using a Gas Chromatograph (Agilent 6890N) with HP-5 fused silica column of dimensions 30 m 250 µm 250 µm film thickness and 5% phenyl methyl siloxane capillary column. The oven temperature programme was maintained at 40 0 C for 2 min and then increased at a rate of 10 0 C/min until a final temperature of C was reached. The final temperature was held for 2 min with Nitrogen carrier gas held at a constant flow rate of 2.6 ml/min and pressure of 10.4psi. The PAHs 4.0 Results and discussion

3 International Journal of Advancements in Research & Technology, Volume 6, Issue 2, February Aliphatic Hydrocarbons (mg/kg) Sample C 8 C 10 C 12 C 14 C 17 Pr C 18 Ph C 22 C 23 C 24 C 29 C 30 BH1: molecular and moderate molecular weight hydrocarbons was lower in the surface (0-15 cm) with the light molecular weight hydrocarbon dominant, while it was higher for the deeper samples with the moderate molecular weight hydrocarbon dominant as shown in fig.2 1: cm BH2: BH2: Polycyclic Aromatic Hydrocarbons (mg/kg) Sample ID Nap Ace Fluo Ph An Fl Py BaA Chr BH1: C8 C10 C12 C14 C17 Pr C18 Ph C22 C23 C24 C29 C30 BH1: BH2-15CM BH2: BH2-30CM BH2: Table.1.0 Concentration of hydrocarbon components in the soil Hydrocarbon profile in the soil: The soil samples from BH1 show the distribution of the hydrocarbon compounds inferring that the lighter molecular weight hydrocarbon (nc 8 nc 14 ) were slightly more abundant in the upper 0-15 cm depth soil while the moderate molecular weight compounds (nc 17 nc 20 ) were more abundant in the deeper 15-30cm depth soil. The profile for BH2 also show the same trend, however, the nc 8 nc 12 hydrocarbon were relatively absent, nonetheless, nc 17 nc 20 moderate molecular weight hydrocarbons were observed to be more abundant in the subsurface (15-30 cm). It was observed for both samples (BH1 and BH2) that the relative differences in the quantity of light Fig.1 Clustered column plots of TPH distribution in soil samples (BH1) and (BH2).

4 International Journal of Advancements in Research & Technology, Volume 6, Issue 2, February This may infer that the lighter molecular weight hydrocarbon, which could have remain in the shallower depth, could have been degraded by microbes, since Chr biodegradation is enhanced in media where there is BaA availability of oxygen. [3]. Physical weathering such as Py vapour pressure, temperature could have aided the FL Anth evaporation of the lower molecular weight hydrocarbons on Phen the soil surface. The fact that there are higher amount of oil Fluo residue in the subsurface soil samples (15-30 cm) in the AceNapylene Nap study site could be explained by the Exxon Valdez spill case, where 24 years after the oil spill event oil residues still persisted on shorelines and subsurfaces, trapped in BH1-30CM heterogeneous low permeability sediment overlaid by high permeability sediment [1]. The TPH concentrations in the soil after remediation at both 0-15 cm and cm depth at both sites 1 and 2 (BH1 and BH2) are thus: 0-15 cm at site 1 = mg/kg cm at site 1 = mg/kg 0-15 cm site 2 = mg/kg cm site 2 = mg/kg The TPH concentration of the soil at sites 1 (BH1) and 2 (BH2) both for shallow (0-15 cm depth) and for deeper depths (15-30 cm) were all higher than the threshold values for the target value which 50 mg/kg. This infers that the remediation exercise was not performed to a satisfactory limit. The target value of 50 mg/kg was not realized; hence, the soil has not attained the soil quality required for the full Fig. 2. Clustered column plots of PAHs distribution in soil restoration of the soil s functionality for human, animal and samples (BH1) and (BH2). plant life. This means that the soil is still harmful to life forms given the hydrocarbon content of the soil. The distribution of the aromatic hydrocarbon in the samples of the two sites (BH 1 & 2) as shown in fig. 2. show that the PAH lighter fractions such Naphthalene, Acenaphthylene, Fluorene were more abundant in the deeper sample (15-30 cm) relative to the shallower sample, while the heavier molecular weight compounds such as benzo (a) anthracene and chrysene were more abundant in the surface samples (0-15 cm) relative to the subsurface sample. The amount of hydrocarbon in the soil was approximately mg/kg for 0-15 cm depth sample and mg/kg for the cm depth sample for BH1.

5 International Journal of Advancements in Research & Technology, Volume 6, Issue 2, February Also, fig. 2 shows the distribution of aromatics in the soil in [4] Brown GS, B. L. (2003). Permanganate oxidation of site 2 (BH 2). The distribution showed that the lighter sorbed polycyclic aromatic hydrocarbons. Waste aromatic hydrocarbon such as Naphthalene, Acenaphthylene, Manage, 23: Fluorene, and Anthracene are more abundant in the subsurface [5] Chaillan F, C. C. (2006). Factors inhibiting sample (15-30 cm) while the heavier polycyclic aromatic hydrocarbon are abundant in the shallower depth (0-15 cm). This could be explained by the fact that concentration of the polycyclic aromatic hydrocarbons in the shallow depth (0-15cm) are less by one degree of magnitude compared to that in the subsurface (15-30cm). This infers that most of the polycyclic aromatic compounds in the shallow sample have [6] [7] bioremediation of soil contaminated with weathered oils and drill cuttings. Environ Pollut, 144: Clark, R. (1982). Biological effects of oil pollution. Wat. Sc. Tech, 14,: Khan FI, H. T. (2004). An overview and analysis of site remediation technologies. J Environ Manage, 71: been degraded, since the presence of oxygen and [8] Liu B, B. M. (2001). Effects of soil water content on microorganisms enhances PAH degradation in the soil [9]. biodegradation of phenanthrene in a mixture of organic contaminants. Soil Sediment Contam, 10: 5.0 Conclusion: The implication of hydrocarbon in the soil after remediation [9] Li, X., Li, P., Lin, X., Zhang, C., Li, Q., Gong, Z., insinuates that, the hydrocarbon content of the soil at sites Biodegradation of aged polycyclic aromatic BH1 and BH2 for both surface (0-15cm depth) and for hydrocarbons (PAHs) by microbial consortia in soil subsurface depth (15-30cm) were all higher than the and slurry phases. EGASPIN target value of 50.0 mg/kg. This can also be the Journal of Hazardous Materials 150: case in some other locations in Ogoni where mechanical [10] Osuji Leo.C, Iniobong D, Idung, and Chukwunnonye remediation was used. M. Ojinnaka (2006): Hydrocarbon Speciation by This infers that the remediation exercise was not performed to Fingerprinting Technique and Diagnostic a satisfactory limit. The target value of 50.0 mg/kg was not Vanadium/Nickel Ratio of Mgbede-20 Oil-Impacted realized; hence, the soil has not attained the required quality Site in the Niger Delta Basin of Nigeria. for restoration of the soil s functionality for human, animal Environmental Forensics, 7: and plant life. [11] [11] UNEP. (2011). Environmental Assessment of Ogoniland. Report. Washington DC: United nations Environmental Programme. References: [1] Abrakasa, S. (2013). Remediating Environmental pollution by Petroleum exploration: The Nigerian Perspective. Advances in Environmental and Chemical pollution studies, 1: [2] Atlas, R. (1995). Petroleum biodegradation and oil spill bioremediation. Marine Pollution Bulletin, 31: [3] Bento FM, C. F. (2005). Comparative bioremediation of soils contaminated with diesel oil by natural attenuation, biostimulation and bioaugmentation. Bioresour Technol, 96: [12] Vladimir et al. (2012): Gas Chromatography in Environmental Sciences and Evaluation of Bioremediation, Gas Chrototography-Biochemicals, Narcotics and Essential Oils, (Ed).pp1-11. [13] Wang, Z. F. (1998). Study of the 25years old oil spill: Persistence of oil residues and comparison between surface and subsurface sediments. Environmental science Technology, 32: [14] Wang, Z. F. (1995). Study of the effects of weathering on chemical composition of a light crude oil using GC-MS/GC-FID. J. Microcolumn Separations, 7 (6),

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