Total Extractable Hydrocarbons Research Articles

Updating risk remediation-endpoints for petroleum-contaminated soils? A case study in the Ecuadorian Amazon region

In Ecuador, the regulatory framework for the remediation of petroleum-contaminated soils is based on predefined concentration endpoints for a selected range of petroleum hydrocarbon compounds. However, such approach may lead to over or under-estimation of the environmental risk posed by contaminated soils. In this study, the end-point remediation criteria according to Ecuadorian Environmental legislation were evaluated using different approaches. The first one was based on Total Extractable Petroleum Hydrocarbons (TEPH) and the second one on Total Bioavailable Petroleum Hydrocarbons (TBPH). Both were compared with ecotoxicological determinations using EC50 -Microtox® bioassay at 5 and 15 min of exposure. The correlation (R2) between EC50 values vs TEPH was of 0.2 and 0.25 for 5 and 15 min, respectively. Meanwhile, R2 between EC50 and TBPH was of 0.9 and 0.65 for 5 and 15 min, respectively, demonstrating a stronger correlation. Our results suggest that a contaminated site where the concentration of the TEPH is higher than the relevant regulatory concentrations may be deemed to present an acceptable risk even though their concentrations exceed the target values in soils. The results also challenge the notion that hormesis is associated with TEPH, contrary to some literature. This study is the first in Ecuador to propose incorporating bioavailability into environmental regulations, highlighting the need for further research to establish realistic and achievable remediation goals based on toxicity studies involving various trophic levels.

Hydrocarbon Profile of Oil-Spill-Impacted Soils from Ogoni in Rivers State, Nigeria

This research examined the total extractable hydrocarbon content comprising of polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPHs), total hydrogen carbon (THC) and total organic nitrogen (TON) of an oil-spill-impacted site in Ogoni land, Okenta Alode, Eleme local government area, Rivers state, Nigeria. Sediment samples of crude oil hydrocarbon contaminated soils were randomly collected from different points at the study sites. Samples were collected between 0 - 15cm (surface m level) and 15 - 30cm (in-depth level) with soil auger and thereafter bulked to obtain composite sample. Bio remediated soil, obtained at about 200 m away from the contaminated site was also collected making a total of twelve (12) samples, with the coordinates of the locations recorded with a GPS device. The samples collected in sterile non-reactive polythene bags and transported using icepacks to the laboratory for analyses and the sediments stored at 6°C and extracted within 14 days of collection. The result of the study revealed among others that the oil-spill-impacted sites contain high concentration of TPH, as the highest concentration obtained from the different sites was 298.57 mg/kg and the lowest was 100.80 mg/kg. Also, the in-depth samples contain higher concentrations than the surface level samples, while similar results were also observed for PAHs and THC. The THC values for surface level samples are in the order of P3/S/O2 (129.000 mg/kg) > P5/S/O1 (229.300 mg/kg) > P1/S/O1 (232.200 mg/kg) > P4/S/O1 (256.111 mg/kg) > P2/S/O1 (303.100 mg/kg). The PAHs concentration in the sediment were within the acceptable limits and showed trend of DBA > Chr > BbFL > Ind > BaA > BkFL > Pyr > Fl > Flu > Ant > AcPY > Phen > AcP > NaP. There was no non-carcinogenic and carcinogenic risk posed to the populace as a result of PAHs contamination. Thus, the result suggest that these sediments may be contaminated with PAHs, TPH and THC and has reduced TON due to hydrocarbon contamination which may reduce plant growth in the study area. It recommends that these contaminations resulting from hydrocarbons be contained to prevent it from resulting to deleterious health effects to the exposed populace.

Exploration of Extraction and Separation Techniques for Routine Trace Analysis of Organic Compounds in Water: Dispersive Liquid-Liquid Microextraction vs Liquid-Liquid Extraction

Dispersive liquid-liquid microextraction (DLLME) was compared to liquid-liquid extraction (LLE) in terms of the methods’ abilities to analyze samples and ultimately to provide information to an analyst. A simple method of relative quantification by compound class approximation was introduced and its validity tested, while the merits of comprehensive gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS) were exhibited on multiple sets of locally obtained environmental water samples. 20 classes of compounds were effectively identified by the DLLME-GC×GC-TOFMS protocol proposed. The limits of detection (LOD) of the protocol ranged between 17 and 377 times lower than the conventional protocol designed for targeted total extractable hydrocarbon (TEH) and total petroleum hydrocarbon (TPH) analysis, with LODs of selected compounds between 0.08 and 1.0 µg/L. Relative quantification shows promising results and was used for quantification of non-targeted analytes within real samples. This quantification method will be used to inform future work to be implemented in industrial environmental analysis.

Investigation of Dioctyl Sodium Sulfosuccinate in Demulsifying Crude Oil-in-Water Emulsions.

This research investigated the performance of dioctyl sodium sulfosuccinate (DSS), a double-chain anionic surfactant, in breaking crude oil-in-water emulsions. The response surface methodology was used to consider the effect of the DSS concentration, oil concentration, and shaking time on demulsification efficiency and obtain optimum demulsification conditions. Further single-factor experiments were conducted to investigate the effects of salinity, crude oil conditions (fresh and weathered), and gravity separation settling time. The results showed that DSS efficiently demulsified stable emulsions under different oil concentrations (500–3000 mg/L) within 15 min shaking time. Increasing DSS concentration to 900 mg/L (critical micelle concentration) increased the demulsification efficiency to 99%. DSS not only improved the demulsification efficiency but also did not impede the demulsifier interfacial adsorption at the oil–water interface due to the presence of the double-chain structure. The low molecular weight enables the homogeneous distribution of DSS molecules in the emulsion, leading to a high demulsification efficiency within 15 min. Analysis of variance results indicated the importance of considering the interaction of oil concentration and shaking time in demulsification. DSS could reduce the total extractable petroleum hydrocarbons in the separated water to <10 mg/L without gravity separation and could achieve promising demulsification performance at high salinity (36 g/L) and various concentrations of fresh and weathered oil. The demulsification mechanism was explained by analyzing the microscopic images and the transmittance of the emulsion. DSS could be an efficient double-chain anionic surfactant in demulsifying stable oil-in-water emulsions.

Effects of gas pressurization on the interpretation of NMR hydrocarbon measurements in organic rich shales

The estimation of total hydrocarbons (HCs) in place is one of the most important economic challenges in unconventional resource plays. Nuclear magnetic resonance (NMR) has proven to be a valuable tool in directly quantifying both hydrocarbons and brines in the laboratory and the field. Some major applications of NMR interpretation include pore body size distributions, wettability, fluid types, and fluid properties. However, for tight formations, the effects of the factors on NMR relaxation data are intertwined. One purpose of this study is to review the interpretation of NMR response of HCs in a tight rock matrix through illustrated examples. When comparing NMR data between downhole wireline and laboratory measurement, three important elements need to be considered: 1) temperature differences, 2) system response differences, and 3) pressure (mainly due to the lost gasses.) The effect of temperature on HCs would be presented with experimental results for bulk fluids. Whereas, the effect of pressure is investigated by injecting gas back into rock matrix saturated with original fluids. The experiments were performed within an NMR transparent Daedalus ZrO2 pressure cell, which operates at pressures up to 10,000 psi. The results show that, at ambient temperature and pressure, NMR responds to a fraction of HCs, which is volatile enough to be observed as an NMR relaxation sequence. The invisible fraction of HCs to NMR sequence at ambient condition can be up to 20% of the total extractable HCs. Molecular relaxation is impacted by fluid viscosity, pore size, and surface affinity. In other words, the fluid with higher viscosity (either due to temperature or gas loss), presenting in smaller pore, or highly affected by the pore surface, will relax faster, and would be partially invisible to NMR, especially in the field. This is critical to the interpretation of NMR response for liquid rich source rocks, in which all of the above molecular relaxing restrictions can be found. Thus, engineers can underestimate movable HCs by using routine core analysis data.

Capture of stormwater runoff and pollutants by three types of urban best management practices

Land cover changes associated with urbanization produce hydrological alterations, which often diminish infiltration, leading to increased runoff volumes, peak flows, and greater need for pollution control. A number of urban “green infrastructure” best management practices (BMPs) have been designed to capture and contain stormwater runoff near the source. Although implementation of such practices has slowly increased, lack of evidence about their effectiveness in reducing the quantity and improving the quality of stormwater runoff may still limit the degree to which they are implemented. The objectives of this study were to assess performance of three types of urban stormwater BMPs by measuring their soil characteristics, infiltration rates, runoff reduction, and water quality parameters compared to adjacent contributing areas. Three types of practices—bioretention cells, native landscaping (reconstructed prairie areas), and three-zone vegetated riparian buffers located in Ames and Ankeny, Iowa—were assessed by conducting infiltration tests and collecting soil and water samples. For the biocells in particular, practice surface areas were smaller in relation to their contributing areas than is recommended in current design criteria. On average, the bioretention cells and the buffers9 wooded zones had significantly lower soil bulk densities, higher infiltration rates, and smaller runoff volumes than those of contributing areas. Time-to-runoff was particularly high for bioretention cells. Infiltration characteristics of the native landscapes (reconstructed prairie) and buffer prairie zones we studied were not significantly different from those of the contributing areas. Total extractable hydrocarbon concentrations were elevated in the bioretention cells, while metals such as chromium (Cr) had greater concentrations in the contributing areas. Based on these findings, we recommend careful attention to sizing, particularly for biocells, and suggest routine incorporation of soil amendments (such as compost) to improve the performance of reconstructed prairie areas. Our findings also suggest that more widespread implementation of these source-control measures in retrofit of existing developments and/or in the design of newly urbanizing areas will be effective for reducing stormwater runoff volumes and improving water quality.

Changes in the fingerprint of oil derived substances in the sediments of the Bílina River

The aim of this study was to evaluate the changes in the presence of the crude oil derived substances in the Bilina River sediments and to verify explanatory abilities of the used analytical methods. The Bi­lina River has its source on the slopes of Krusne hory and flows to the east through surface pits in an artificial corridor in its upper stream and further continues through the open landscape of the North Bohemian brown coal basin. The primary factor determining the current appearance of the landscape is human activity and anthropogenic embankments. The area along the Bi­lina River is loaded by the opencast brown coal mining and coal processing, petroleum refineries, and chemical plants. There are major industrial operations in the basin of the River Bi­lina which are particularly co-responsible over a long term for high levels of persistent organic pollutants and inorganic pollutants in the river sediments. Twenty samples of river sediments were collected along the Bi­lina River. All samples were subjected to the determination of the total extractable hydrocarbons, the total organic carbon, the total sulphur, and the sum of the polycyclic aromatic hydrocarbons(PAH). According to Herron (1988) most of the analysed samples belong to the shales or Fe-shales where a great possibility of sorption of inorganic or organic pollutants is expected. To distinguish the river segments with the prevailing input of the petrogenic from pyrogenic substances, correlation of the total extractable hydrocarbons and PAH were applied. The ratio fluoranthen / pyren, whose value from the anthropogenically modified flow in the segment Zaluži - Bi­lina did not go beyond 0.5 which is significant for the presence of the emissions from the transport or the petroleum industry, has been proved superior to the other currently recommended ratios of PAH. The evaluation of the archival TEH data did not show any improvement of the water and sediment quality along the Bi­lina river profile.

Investigating physiological, cellular and molecular effects in juvenile blue crab, Callinectus sapidus, exposed to field-collected sediments contaminated by oil from the Deepwater Horizon Incident

Juvenile blue crabs, Callinectus sapidus, were exposed for 31days to six different sediments collected within the Pass a Loutre State Wildlife Management Area approximately 6months or 1.5years post-capping of the Macondo-252 well-head following the Deepwater Horizon (DWH) Incident. Based on forensic analysis to fingerprint for DWH oil, these sediments differed in their levels of DWH oil contamination, and included one reference sediment collected from a location with no detectable DWH oil present. The concentration of 50 individual parent and alkylation group polycyclic aromatic hydrocarbons (PAHs), saturated hydrocarbons (37 total), and total extractable hydrocarbons were determined in each sediment, as were biologically relevant metals, grain size distribution, percent total organic carbon, and percent total solids. Total concentrations of 50 PAHs (TPAH50) of initial treatment sediments ranged from 187μgkg−1 (reference site) to 2,086,458μgkg−1 (the highest DWH oil contaminated site). Multiple biological endpoints were measured including mortality, growth, and ecdysis. Additionally, early biomarkers of biological stress were examined in the hemolymph and hepatopancreas of crabs, including DNA damage (Comet assay) and expression of genes encoding Cu-metallothionein (CuMT), glutathione-S-transferase (GST), and manganese superoxide dismutase (MnSOD). Over the 31day exposure, there were no treatment related mortalities in juvenile blue crabs. The overall growth and molting of the crabs were not substantially different between the various sediment exposures over the exposure period. Additionally, none of the early biomarkers of biological stress were correlated with PAH concentrations. Overall, juvenile blue crabs did not appear to be negatively impacted during the 31day exposure by DWH oil contaminated sediments collected at least 6months post-capping of the Macondo-252 well-head.

Evaluation of the actual standard procedures for analysis of total extractable hydrocarbons in environmental water matrices

Hundreds of different hydrocarbon compounds derived from agricultural, industrial and domestic practices are released daily into aquatic systems with adverse effects in the desirable potable characteristics, in aquatic fauna and flora, and on tourism, recreation and aesthetics of the impacted areas. Total petroleum hydrocarbon concentration data cannot be used to quantitatively estimate human health risk, but can be used as an important tool for three purposes: verifying if there is a problem, assessing the severity of the contamination and following the progress of a remediation effort. The objective of this work was the optimization of the experimental conditions for the determination of total hydrocarbons in water by liquid–liquid extraction coupled to infrared spectrophotometry, with the goal of improving the qualitative information provided by the spectra. The method was validated with satisfactory detection and quantification limits and demonstrated acceptable levels of precision, accuracy and analyte recoveries. Solid phase extraction and microwave assisted extraction procedures were tested and compared to the liquid extraction. Additionally, a spectra library was prepared with different natural and synthetic oils. The developed method was applied to the analysis of Portuguese inland and coastal bathing waters and wastewaters and their compliance with national and European legislation was assessed.

Self-Sustaining Smoldering Combustion: A Novel Remediation Process for Non-Aqueous-Phase Liquids in Porous Media

Smoldering combustion, the slow burning process associated typically with porous solids (e.g., charcoal), is here proposed as a novel remediation approach for nonaqueous phase liquids (NAPLs) embedded in porous media. Several one-dimensional vertical smoldering experiments are conducted on quartz sand containing fresh coal tar at an initial concentration of 71 000 mg/kg (approximately 25% saturation) and employing an upward darcy air flux of 4.25 cm/s. Following a short-duration energy input to achieve ignition at the lower boundary, a self-sustaining combustion front is observed to propagate upward at 1.3 x 10(-2) cm/s. The process is self-sustaining because the energy released during NAPL smoldering is efficiently trapped and recirculated by the soil matrix, preheating the NAPL ahead of the reaction front. The smoldering process is observed to self-terminate when all of the NAPL is destroyed or when the oxygen source is removed. Pre- and post-soil analysis revealed that NAPL smoldering reduced the concentration of total extractable petroleum hydrocarbons (TPH) from 38 000 mg/kg to below detection limits (< 0.1 mg/kg) throughout the majority of the column. A comparable experiment in which conductive heating is applied in the absence of smoldering demonstrates a 6-fold reduction in the net energy in the system and residual TPH values of 2000-35 000 mg/kg. A further repeat in which the air supply is prematurely terminated demonstrated that the NAPL smoldering process can be extinguished via external control. A suite of 23 demonstration experiments shows that NAPL smoldering is successful across a range of soil types (including simple layered systems) and contaminants (including laboratory mixtures of dodecane, DCA/ grease, TCE/oil, vegetable oil, crude oil, and mineral oil) as well as field-obtained samples of materials containing coal tar, oil drill cutting waste, and oil sands.

Distribution and Weathering of Crude Oil Residues on Shorelines 18 Years After the Exxon Valdez Spill

In 2007, a systematic study was conducted to evaluate the form and location of residues of oil buried on Prince William Sound (PWS) shorelines, 18 years after the 1989 Exxon Valdez Oil Spill (EVOS). We took 678 sediment samples from 22 sites that were most heavily oiled in 1989 and known to contain the heaviest subsurface oil (SSO) deposits based on multiple studies conducted since 2001. An additional 66 samples were taken from two sites, both heavily oiled in 1989 and known to be active otter foraging sites. All samples were analyzed for total extractable hydrocarbons (TEH), and 25% were also analyzed for saturated and aromatic hydrocarbon weathering parameters. Over 90% of the samples from all sites contained light or no SSO at all. Of samples containing SSO, 81% showed total polycyclic aromatic hydrocarbon (TPAH) losses greater than 70%, relative to cargo oil, with most having >80% loss. Samples with SSO were observed in isolated patches sequestered by surface boulder and cobble armoring. Samples showing lowest TPAH loss correlated strongly with higher elevations in the intertidal zones. Of the 17 atypical, less-weathered samples having less than 70% loss of TPAH (>30% remaining), only two were found sequestered in the lower intertidal zone, both at a single site. Most of the EVOS oil in PWS has been eliminated due to natural weathering. Some isolated SSO residues remain because they are sequestered and only slowly affected by natural weathering processes that normally would bring about their rapid removal. Even where SSO patches remain, most are highly weathered, sporadically distributed at a small number of sites, and widely separated from biologically productive lower intertidal zones where most foraging by wildlife occurs.

Analyzing Analytical Laboratory Results: An Environmental Practitioner's Perspective

This paper describes a study of the variation in measured total extractable hydrocarbon (TEH) concentrations among soil sub-samples removed from standard 125-mL glass jars. It aims at addressing the frequently observed discrepancies in laboratory chemical analysis results from ordinary and duplicate soil samples. It also investigates if a modified laboratory sub-sampling procedure using a jar template would yield a more representative TEH concentration in soil samples. Through the study, it was determined that TEH concentrations may vary up to 200% within a soil sample contained in a standard sample jar, making laboratory sub-sampling a potentially large source of error in the measurement process of soil samples. It was also determined through statistical analysis that the proposed grid sub-sampling procedure and the current haphazard sub-sampling procedure employed in laboratories did not yield significantly different analytical results. The magnitude of TEH method specific measurement uncertainties, on average, accounted for 41% of the TEH analytical value. This brought into question the analytical method suitability and the application of measurement uncertainties to single-value regulatory criteria for environmental practitioners.

Concentration and character of PAHs and other hydrocarbons in coals of varying rank – Implications for environmental studies of soils and sediments containing particulate coal

Particulate coal can occur in soils and sediments from both natural and anthropogenic sources. Its presence can influence the concentrations of regulated and more bioavailable pollutants through its geosorbent qualities and its own contribution of total extractable hydrocarbons (TEH), including polycyclic aromatic hydrocarbons (PAHs) and biomarkers. Extractable PAHs in coal also can potentially affect PAH-based “source” and “maturity” ratios of soil or sediment extracts, which can be used to assess the source(s) of PAHs. This study reports on the absolute concentrations of TEH, the 16 Priority Pollutant PAHs, 27 alkylated PAHs and sulfur containing aromatics, and selected biomarkers in 15 coals ranging in rank from lignite to anthracite. Unlike most previous studies in the fuel science or geochemical literature the coals herein were extracted using dichloromethane at room temperature, an EPA Method 3500 type method common in environmental laboratories, thereby allowing comparison of these results to environmental studies. The concentrations of TEH ranged from 8.2 to 2500 μg/g coal (dry wt) with a maximum yield among high volatile bituminous coals. The TEH “fingerprints” were variable and some of these resembled those of other forms of contamination. The concentrations of Priority Pollutant PAHs ranged from 35 to 11,000 ng/g coal (dry wt) or 38 to 12,000 ng/g carbon and varied with coal rank, reaching a maximum within the high volatile bituminous rank. The distributions of extractable PAHs and numerous PAH ratios conventionally used as “source” and/or “maturity” parameters also varied with coal rank emphasizing that particulate coal in soils and sediments cannot be universally represented by a single set of diagnostic parameters. Hopanoid and sterane biomarker yields also varied with rank, reaching a maximum in high volatile bituminous coals, and were low relative to PAHs. Because particulate coal often co-occurs with other sources of hydrocarbons in soils and sediments, the data presented herein may prove useful in allocating coal versus non-coal sources on a mass balance basis.

Characterization and Source of Unknown “Tar-Like Material” and “Slag” in a Former Oil Field in Compton, California

The discovery of “tar-like material” and “slag” within a ravine traversing a mobile home park and former oil field promulgated its remediation and a subsequent lawsuit brought by the park's owner against the former Dominquez Oil Field (Compton, CA) operator claiming these materials were derived from historic oil production operations. In this study, archived samples of these materials from the (remediated) ravine were characterized for their physical (density, microscopic character, magnetic properties, and float-sink behavior) and chemical properties, the latter including chemical fingerprinting of the total extractable hydrocarbons, polycyclic aromatic hydrocarbons, and petroleum biomarkers, to determine their nature and source(s). Physical testing confirmed the “slag” was iron and/or steel (ferrous) slag that had experienced variable cooling histories. A chemical fingerprinting comparison of the “tar-like material” and Dominquez Field (Monterey Formation) crude oil revealed that the crude oil—or its weathered equivalent—was not the source of the tar-like material. The tar-like material exhibited evidence of heating consistent with a distillation residuum—the heavy fraction(s) of a distilled crude oil produced during refining. The most likely source of the tar-like material is a refined petroleum asphalt. The co-occurrence of ferrous slag—a common road asphaltic concrete aggregate and road base—and petroleum asphalt in the site's ravine was reconciled as being most likely derived from recurrent road-paving operations that occurred at the mobile home park in the 1980s—and not from historic oil field operations.

Hydrocarbon contamination of a terrestrial ecosystem: the case of Oshire-2 oil spill in Niger Delta, Nigeria

An oil-impacted site at Oshire-2 in Niger Delta (Nigeria) was delimited by reconnaissance. Surface and subsurface soils were analyzed for total extractable hydrocarbon content and some physicochemical characteristics. The oil-impacted soils had a mean hydrocarbon content of 1.99 × 103 mg/kg (no overlap in Standard Error at 95% Confidence Limit) and were characterized by an isohyperthermic temperature regime >22°C, high moisture content, high acidity (low soil-pH) and low electrical conductivity. The intense infusion of degradable hydrocarbons at the site must have stimulated aerobic and anaerobic microbial metabolism and so, as oxygen became limiting, utilization of alternate electron acceptors produced an increasingly reducing environment.

Hydrocarbon contamination of a typical mangrove floor in Niger Delta, Nigeria

The impact of petroleum hydrocarbons on the floor of a mangrove system located on one of the intertidal lands behind the barrier islands of Niger Delta basin of southern Nigeria was evaluated following the Obiafu-14 oil spillage. The area covered by the oil spill was delimited by reconnaissance and soils were sampled by grid method from the bottom and middle slopes of oil-affected and unaffected (control) sites. Soil samples were later brought to the laboratory where total hydrocarbon content was determined by extraction and spectrophotometric techniques. A lower pH range of 4.28–4.36 in the oil impacted soils meant that the site was more acidic; a higher moisture content of 33.34% and lower electrical conductivity (EC) of 31.75μS/cm in the affected area presupposed oxygen deprivation and lower salt content respectively. On the strength of the baseline data on the study area and evidence from the uncontaminated, geographically similar control site, it can be said that the Obiafu-14 oil spillage had severely contaminated the affected mangrove floor. This is corroborated by a total extractable hydrocarbon content of 6.32×103 ± 344 mg/kg (no overlap in Standard Error at 95% Confidence Limit), and the abysmal degradation of the mangrove system at the site. Although soils of the mangrove floor under consideration may well be of limited cultivation value on account of the people’s dual occupation in fishing and farming, the presence of such levels of petroleum hydrocarbons at the study site might hamper agricultural productivity.

Physical and chemical factors affecting microbial biomass and activity in contaminated subsurface riverine sediments

Over 80 years of direct discharge of industrial effluents into the Mahoning River, located in northeastern Ohio, USA, has led to the accumulation of a wide variety of pollutants within its sediments. This study examined the physical and chemical parameters, including lipophilic pollutants, affecting microbial activity and biomass in subsurface (10-40 cm horizon) sediments. Microbial biomass was higher in anthropogenically contaminated sediments, and step-wise linear regression showed that approximately 82% of the variation in microbial biomass could be explained by total hexane extractable hydrocarbons, sediment particle size, and water content. There was no correlation between microbial activity and biomass. Independent variables influencing anaerobic activity were temperature and water holding capacity. The results of this study indicate that freshwater, sedimentary anaerobic microbial communities respond to a range of environmental parameters, many of which influence subsurface river sediments, and that lipophilic pollutants, when present, can cause increases in total microbial biomass.

Preliminary Investigation on Mgbede‐20 Oil‐Polluted Site in Niger Delta, Nigeria

Soil physicochemical properties (pH, electrical conductivity (EC), % moisture, total organic carbon (TOC), total organic matter (TOM)), total extractable hydrocarbon content (THC), and micronutrient (Mn, Fe, Cu, Zn) levels of the Mgbede-20 oil-impacted site in Niger Delta, Nigeria, were investigated. Both oil-impacted and their background control soils were found to be acidic especially at surface depth. A slightly higher EC value of 107.4+/-15.0 microS cm(-1) was obtained for the subsurface-polluted soils. Of the micronutrients investigated, only Fe exceeded its acceptable limit (>100 mg/kg). The observed increase in moisture content resulting from the oil's aggregation of soil particles may lower soil porosity, and increase resistance to penetration and hydrophobicity. Soil pH can be adjusted by aeration to complete the microbially mediated oxidation of the organic acids, followed by the addition of agricultural lime to provide some buffering capacity to the soil.

Assessment and Treatment of Hydrocarbon Inundated Soils Using Inorganic Nutrient (N-P-K) Supplements: II. A Case Study of Eneka Oil Spillage in Niger Delta, Nigeria

Polluted soils from Eneka oil field in the Niger delta region of Nigeria were collected two months after recorded incidence of oil spillage as part of a two-site reclamation programme. The soils were taken on the second day of reconnaissance from three replicate quadrats, at surface (0-15 cm) and subsurface (15-30 cm) depths, using the grid sampling technique. Total extractable hydrocarbon content (THC) of the polluted soils ranged from 1.006 x 10(3)-5.540 x 10(4) mg/kg at surface and subsurface depths (no overlap in Standard Errors at 95% Confidence Level). Greenhouse trials for possible reclamation were later carried out using (NH(4))(2)SO(4), KH(2)PO(4) and KCl (N-P-K) fertilizer as nutrient supplements. Nitrogen as NO(3)-N and potassium were optimally enhanced at 2% (w/w) and 3% (w/w) of the N-P-K supplementation respectively. Phosphorus, which was inherently more enhanced in the soils than the other nutrients, maintained same level impact after 20 g treatment with the N-P-K fertilizer. Total organic carbon (%TOC), total organic matter (%TOM), pH and % moisture content all provided evidence of enhanced mineralization in the fertilizer treated soils. If reclamation of the crude oil inundated soils is construed as the return to normal levels of metabolic activities of the soils, then the application of the inorganic fertilizers at such prescribed levels would duly accelerate the remediation process. This would be, however, limited to levels of pollution empirically defined by such THC values obtained in this study. The data on the molecular compositional changes of the total petroleum hydrocarbon content (TPH) of the spilled-oil showed the depletion of the fingerprints of the n-paraffins, nC(8)-nC(10), and complete disappearance of C(12)-C(17) as well as the acyclic isoprenoid, pristane, all of which provided substantial evidence of degradation.

Influence of substratum on the degradation processes in diesel polluted sub-Antarctic soils (Crozet Archipelago)

Biodegradation by naturally occurring populations of microorganisms is a major mechanism for the removal of oil hydrocarbons from the environment. Therefore, follow-up of bacterial populations and chemical indices of biodegradation are important components of contaminated site assessment studies. Over a 4-year period following an accidental diesel contamination of the sub-Antarctic Crozet Archipelago (51°51′E–46°25′S), a field study was carried out in the contaminated area that is located in a transition zone between an arid fell-field (upstream) and a wet vegetated area (downstream). This study included a monitoring of heterotrophic and hydrocarbon-degrading bacterial abundance and chemical analysis of the remaining hydrocarbons. Significant higher number of heterotrophic and hydrocarbon-degrading bacterial counts revealed a rapid acclimation of sub-Antarctic microbial soil communities to the diesel fuel contamination. A chemical survey conducted during the last 2 years (2002 and 2003) showed that the total extractable hydrocarbons (TPH) content in arid fell field was reduced to ≤50% of their value while it was reduced only to ≤65% in vegetated soil. In addition, the decrease of TPH was always higher in the presence of fertilizer in the arid contaminated area, while fertilizer addition was almost inefficient in the wet contaminated one. All these results demonstrate a serious influence of the soil properties on the degradation rate. However, all chemical indices showed a significant reduction of alkanes and light aromatics in both contaminated area confirming a regular oil degradation process.