Lower Total Petroleum Hydrocarbon Research Articles

Structure and composition of microbial communities in the water column from Southern Gulf of Mexico and detection of putative hydrocarbon-degrading microorganisms.

This study assessed the bacterioplankton community and its relationship with environmental variables, including total petroleum hydrocarbon (TPH) concentration, in the Yucatan shelf area of the Southern Gulf of Mexico. Beta diversity analyses based on 16S rRNA sequences indicated variations in the bacterioplankton community structure among sampling sites. PERMANOVA indicated that these variations could be mainly related to changes in depth (5 to 180 m), dissolved oxygen concentration (2.06 to 5.93 mg L-1), and chlorophyll-a concentration (0.184 to 7.65 mg m3). Moreover, SIMPER and one-way ANOVA analyses showed that the shifts in the relative abundances of Synechococcus and Prochlorococcus were related to changes in microbial community composition and chlorophyll-a values. Despite the low TPH content measured in the studied sites (0.01 to 0.86 μL L-1), putative hydrocarbon-degrading bacteria such as Alteromonas, Acinetobacter, Balneola, Erythrobacter, Oleibacter, Roseibacillus, and the MWH-UniP1 aquatic group were detected. The relatively high copy number of the alkB gene detected in the water column by qPCR and the enrichment of hydrocarbon-degrading bacteria obtained during lab crude oil tests exhibited the potential of bacterioplankton communities from the Yucatan shelf to respond to potential hydrocarbon impacts in this important area of the Gulf Mexico.

Rapid Determination of the Total Petroleum Hydrocarbon Content of Soils by Handheld Fourier Transform Near-Infrared Spectroscopy.

For successful soil remediation and hydrocarbon exploration operations, determining the total petroleum hydrocarbon (TPH) content of soils is an indispensable process step. This paper reports on the performance of a handheld Fourier transform near-infrared (FT-NIR) spectrometer for rapid and quantitative determination of TPH content of soils from two different sites by diffuse reflection measurements. For rapid decisions for exploration work or environmental site assessment projects, a quick─preferably on-site─determination of TPH content is valuable. Diffuse reflection NIR spectra were recorded from soil samples of two different sites with TPH reference values ranging from 350 to 30,000 ppm, as determined by capillary gas chromatography and flame ionization detection with hydrocarbon fingerprinting C1-C44. However, this paper not only addresses the development of site-specific partial-least squares (PLS) calibrations but also demonstrates the locally-weighted PLS (LW-PLS) technique, which can be used to develop global, site-independent PLS calibrations without significant penalty in calibration performance. As a first step, the diffuse reflection spectra were used to develop conservative, site-specific PLS calibration models with root-mean-square calibration/cross-validation errors (RMSEC/RMSECV) of 1043/1106 and 741/785 ppm TPH, respectively, and the average absolute prediction errors for samples not contained in the calibration set were 451 and 293 ppm for the two sites, respectively. In a further step, significant degradation of the RMSE values of a conservative PLS model based on the NIR spectra of both sites was then compared to the application of the LW-PLS method, with only a slight loss of the prediction accuracy relative to the site-independent models. This study confirms the ability of next-generation portable FT-NIR spectrometers to predict low TPH levels in various soil types through both─soil-specific and site-independent─calibrations, giving these spectrometers the potential to become rapid screening tools in the field.

Germination Capacity of Helianthus annuus Less Seeds on Soil Media Contaminated by Waste

Used oil waste is often dumped on the ground around the workshop, causing soil pollution which can reduce the function of the soil. The most difficult contaminants in used oil waste to decompose are hydrocarbon compounds, which are highly toxic, polycyclic aromatic hydrocarbons (PAHs). The concentration of oil hydrocarbon contaminants in a sample is determined by measuring the total petroleum hydrocarbon (TPH) concentration. This study was conducted to determine the germination ability of Helianthus anuus, Less seeds on soil media contaminated with waste oil at different concentrations of Total Petroleum Hydrocarbon (TPH). The results showed that the concentration of TPH in the media could inhibit the speed of seed germination. Treatment with low concentration of TPH 2.7% in the media increased % germination, shoot and root length and sprout biomass compared to the medium/intermediate (8.00%) and high (12.26%) TPH treatments and controls. However, there was no significant difference between all treatments regarding germination time and shoot length, although in the low TPH treatment (2.70%) there was a tendency for germination time to be faster than the other treatments, as well as to shoot length which was longer than the other treatments. The higher TPH concentration in the media can inhibit germination time, germination percentage, shoot and root length and biomass. Morphological observations of the growth of sprouts showed an inhibition of root hair formation along with the high TPH content in the media, but all treatments did not affect the growth of the shoots.

Degradation of petroleum pollutants in oil-based drilling cuttings using an Fe2+-based Fenton-like advanced oxidation processes.

Oil-based drilling cuttings (OBDC) contain a large amount of total petroleum hydrocarbon (TPH) pollutants, which are hazardous to the environment. In this study, Fe2+-activating hydrogen peroxide (Fe2+/H2O2), peroxymonosulfate (Fe2+/PMS), and peroxydisulfate (Fe2+/PDS) advanced oxidation processes (AOPs) were used to treat OBDC due to the difference in the degradation capacity of TPH caused by the type of free radical generated and effective activation conditions observed for the different oxidants studied. The results showed that the oxidant concentration, Fe2+ dosage, and reaction time in the three AOPs were greatly positively correlated with the TPH removal rate in a certain range. The initial pH value had a significant effect on the Fe2+/H2O2 process, and its TPH removal rate was negatively correlated in the pH range from 3 to 11. However, the Fe2+/PMS and Fe2+/PDS processes only displayed lower TPH removal rates under neutral conditions and tolerated a wider range of pH conditions. The optimal TPH removal rates observed for the Fe2+/H2O2, Fe2+/PMS, and Fe2+/PDS processes were 45.04%, 42.75%, and 44.95%, respectively. Fourier transform infrared spectrometer and gas chromatography-mass spectrometer analysis showed that the alkanes in OBDC could be effectively removed using the three processes studied, and their degradation ability toward straight-chain alkanes was in the order of Fe2+/PMS > Fe2+/PDS > Fe2+/H2O2, among which Fe2+/PMS exhibited the optimal removal effect for aromatic hydrocarbons. Scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction results showed no significant changes in the elemental and mineral composition of OBDC before and after treatment. Therefore, this study provided a theoretical reference for the effective degradation of TPH pollutants in OBDC.

Valorization of petroleum refinery oil sludges via anaerobic co-digestion with food waste and swine manure

Valorization of oil sludge has been gaining attention to improve the sustainability of the petroleum industry. This study aimed to assess the possibility of anaerobic co-digestion of oil scum and secondary sludge with food waste (or swine manure). Oil scum and secondary sludge were obtained from a wastewater treatment plant (WWTP) of a petrochemical plant. Physicochemical properties, hazardous materials, and microbial community were characterized and biochemical methane potential was performed by a simplex-lattice mixture design. More than 87% (wet wt.) of the oil scum consisted of total petroleum hydrocarbons (TPHs) (21,762 mg/L) that are difficult to be degraded by anaerobes. The secondary sludge showed low TPHs (5 mg/L) and a bacterial community similar to that of municipal WWTPs. The heavy metal (Cu, As, Cr, Ni, Mn, Zn, and V) concentrations in the oil scum and secondary sludge were similar (20–600 mg/L). The maximum methane potentials of the oil sludge and secondary sludges were 20 ± 2 and 56 ± 3 mL CH4/g-volatile solid, respectively. The co-digestion with food waste or swine manure led to a synergy effect on methane production of the co-digestion substrate (10–40% increase compared to the calculated value; v/v) by balancing the C/N ratio. Due to the high TPH contents, oil scum is not appropriate for co-digestion. The co-digestion of secondary sludge with food waste and/or swine manure is recommended. It is necessary to consider whether the concentration of heavy metals is at a level that inhibits the anaerobic co-digestion depending on the operating conditions such as mixing ratios and solid contents.

Occurrence, characterization, source, and risk assessment of petroleum-related hydrocarbons in sediments along St. Clair River, Ontario, Canada

Total petroleum hydrocarbons (TPH), n-alkanes, petroleum biomarkers, and polycyclic aromatic hydrocarbons (PAHs) were analyzed in the sediments collected from the shorelines and bottom of St. Clair River, Ontario, Canada. Most of the sampling sites had low TPH (< 20 μg/g). River bottom sediment usually had higher level of TPHs, total alkanes, total biomarkers, and total PAHs than most of the shoreline ones. Mixed biogenic and petrogenic n-alkanes were present in all the sites. Most sites had trace amounts of petroleum biomarkers. Mixed pyrogenic and petrogenic inputs with the predominant petroleum, have contributed to the detected PAHs at all sampling sites. PAHs detected would not show potential toxicity to benthic organisms in all shoreline sampling sites; however, some light molecular weight PAHs (e.g., phenanthrene, 2-methyl naphthalene, and acenaphthylene) are anticipated to have possible adverse impacts to sediment-dwelling organisms in part of the river bottom sediment.

Occurrence, characterization, and ecological assessment of petroleum-related hydrocarbons on the shoreline of Fraser River Delta, British Columbia, Canada

The Fraser River Delta is a unique and dynamic region supporting the diverse ecosystems and habitats in the Canadian West Coast. Total petroleum hydrocarbons (TPH), n-alkanes, petroleum biomarkers, and polycyclic aromatic hydrocarbons (PAHs) were analyzed for the intertidal sediments taken from the shorelines of the Delta area, British Columbia, Canada, to establish the baseline background data. Most of the sampling sites had low TPH (< 40 μg/g); only two samples had TPH from 100 to 150 μg/g. Mainly biogenic n-alkanes were present in all sites. Non-detectable to trace amounts of petroleum biomarkers were found at most sites. Mixed pyrogenic and petrogenic inputs contributed to the presence of PAHs at most sites. PAHs are not present in amounts anticipated negative effects to benthic organisms in all sampling sites, except that benzo (a) pyrene (BaP) from the upper intertidal zone (UIZ) of Burnaby Fraser Foreshore Park may have possible adverse biological effects.

Occurrence, characterization, and ecological assessment of petroleum-related hydrocarbons in intertidal marine sediments of Burrard Inlet, Vancouver, British Columbia, Canada

Total petroleum hydrocarbons (TPH), n-alkanes, petroleum biomarkers, and polycyclic aromatic hydrocarbons (PAHs) were analyzed in the intertidal sediments of Burrard Inlet, Vancouver, British Columbia, Canada. Most of the sampling sites had low TPH (<40 μg/g). Only 10% of sampling sites, located nearby a harbour and densely populated areas, had relatively high TPH (<260 μg/g). Main biogenic n-alkanes were present in all the sites, except for the main petrogenic input in the sample from the upper intertidal zone (UIZ) of the Maplewood Mudflats. Most sites had trace amounts of petroleum biomarkers. Mixed pyrogenic and petrogenic inputs contributed to PAHs at most sites. PAHs did not show potential toxicity to benthic organisms at most sites; however, possible negative effects from some of the detected PAHs were found for the samples from the UIZs of the Maplewood Mudflats and Labour View Park, and from the lower intertidal zone (LIZ) of Gates Park.

Level of Total Petroleum Hydrocarbon in Fish Samples Smoked with Different Combustible Materials

The determination of total petroleum hydrocarbon (TPH) in smoked fish samples were studied using six combustible materials, such as tyres, lubricating oil, polyvinyl chloride (PVC), plastics, iroko ( chlorophoraexcelsa ) wood and black velvet ( dialiumguineense ) wood. The result of the analysis indicates high TPH of mean value 0.8172g for fish sample smoked with tyre. The low TPH of mean value 0.0679g was obtained from fish sample smoked with iroko wood. This study established the formation of TPH during incomplete combustion of combustible materials used during smoking of fish samples. The associated health hazard of smoked fish were examined. Keywords : Fish samples, Total petroleum hydrocarbon, Combustible materials, Toxicity. DOI : 10.7176/JEES/9-2-06

Enhanced removal of sediment-associated total petroleum hydrocarbons under bioturbation by polychaete perinereis aibuhitensis

Bioturbation processes could influence the physical, chemical and biological properties of aquatic sediments and improve the mineralization of organic matter in sediment. The influence of bioturbation by polychaete Perinereis aibuhitensis on the removal of sediment-associated total petroleum hydrocarbon (TPH) was evaluated through laboratory experiment with P. aibuhitensis cultured in crude oil contaminated coastal sediment. After 60 days, the TPH concentrations in the sediments were significantly decreased compared to the initial concentrations, in which the TPH concentrations in bioturbation experiments (with worms) were significantly lower than those in control experiments (without worms) for both low (1.48 ± 0.19g/kg dry wt) and high (2.67 ± 0.33 g/kg dry wt) TPH-contaminated groups, indicating bioturbation enhanced the removal of TPH in sediment. The TPH removal rates in high TPH group were significantly lower than those in low TPH group, suggested that petroleum pollution inhibited the degradation of petroleum hydrocarbons in sediment. However, the stimulation efficiency was higher in high TPH group than that in low TPH group, which may be the result of enhanced hydrocarbon’s bioavailability by digestive fluid during gut transit.

A study of the 46-year-old Arrow oil spill: Persistence of oil residues and variability in oil contamination along Chedabucto Bay, Nova Scotia, Canada

Abstract The occurrence, spatial distribution and source of petroleum-related hydrocarbons, and the degree of weathering of Arrow oil residues persisting on the shoreline of Chedabucto Bay, Nova Scotia, were assessed. The hydrocarbons assessed included total petroleum hydrocarbons (TPH), n-alkanes from n-C9 to n-C40, petroleum biomarkers like terpanes, hopanes and steranes, non-alkylated polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues (APAHs). Trapped Arrow oil in the sunken tanker has not experienced any marked weathering. The collected environmental samples could be classified into three groups. Group 1 samples were oil free identified by low TPH, highly resolved fractions, a predominantly biogenic source of n-alkanes, and trace amounts of petroleum biomarkers probably from the historical (1970) oil spill. Group 2 samples had higher TPH and the other targets than Group 1 samples. The mixed petrogenic and terrestrial plant inputs were the source of n-alkanes, while the pattern of APAHs indicated that their source varied from site to site, being either recently released petroleum or Arrow oil residues. Group 3 samples mainly contained oil residues from Arrow oil spill, having very high levels of TPH, APAHs and biomarkers; however, most samples were free of n-alkanes. Group 3 samples were mostly found on the southern shoreline of Chedabucto Bay, especially in the upper to middle intertidal zone of the shorelines characterized by mixed pebble/cobble/boulders. The extent of weathering of n-alkanes and APAHs showed no relation to each other, although n-alkanes were depleted more fully than APAHs for most of the oil residues. Thus, various natural attenuation processes, especially for microbial degradation, have contributed to the aging of these oil residues. The degree of weathering varied with different environmental conditions.

Small Purge Method to Sample Vapor from Groundwater Monitoring Wells Screened Across the Water Table

AbstractGroundwater monitoring wells are present at most hydrocarbon release sites that are being assessed for cleanup. If screened across the vadose zone, these wells provide an opportunity to collect vapor samples that can be used in the evaluation of vapor movement and biodegradation processes occurring at such sites. This paper presents a low purge volume method (modified after that developed by the U.S. EPA) for sampling vapor from monitoring wells that is easy to implement and can provide an assessment of the soil gas total petroleum hydrocarbon (TPH) and O2 concentrations at the base of the vadose zone. As a result, the small purge method allows for sampling of vapor from monitoring wells to support petroleum vapor intrusion (PVI) risk assessment. The small purge volume method was field tested at the Hal's service station site in Green River, Utah. This site is well‐known for numerous soil gas measurements containing high O2 and high TPH vapor concentrations in the same samples which is inconsistent with well‐accepted biodegradation models for the vapor pathway. Using the low purge volume method, monitoring wells were sampled over, upgradient, and downgradient of the light nonaqueous phase liquid (LNAPL) footprint. Results from our testing at Hal's show that vapor from monitoring wells over LNAPL contained very low O2 and high TPH concentrations. In contrast, vapor from monitoring wells not over LNAPL contained high O2 and low TPH concentrations. The results of this study show that a low purge volume method is consistent with biodegradation models especially for sampling at sites where low permeability soils exist in and around a LNAPL source zone.

Rapid prediction of total petroleum hydrocarbons in soil using a hand-held mid-infrared field instrument

This manuscript reports on the performance of a hand-held diffuse reflectance (mid)-infrared Fourier transform (DRIFT) spectrometer for the prediction of total petroleum hydrocarbons (TPH) in three different diesel-contaminated soils. These soils include: a carbonate dominated clay, a kaolinite dominated clay and a loam from Padova Italy, north Western Australia and southern Nigeria, respectively. Soils were analysed for TPH concentration using a standard laboratory methods and scanned in DRIFT mode with the hand-held spectrometer to determine TPH calibration models. Successful partial least square regression (PLSR) predictions, with coefficient of determination (R2) ~0.99 and root mean square error (RMSE) <200mg/kg, were obtained for the low range TPH concentrations of 0 to ~3,000mg/kg. These predictions were carried out using a set of independent samples for each soil type. Prediction models were also tested for the full concentration range (0–60,000mg/kg) for each soil type model with R2 and RMSE values of ~0.99 and <1,255mg/kg, respectively. Furthermore, a number of intermediate concentration range models were also generated for each soil type with similar R2 values of ~0.99 and RMSE values <800mg/kg. This study shows the capability of using a portable mid-infrared (MIR) DRIFT spectrometer for predicting TPH in a variety of soil types and the potential for being a rapid in-field screening method for TPH concentration levels at common regulatory thresholds.A novel hand-held mid-infrared instrument can accurately detect TPH across different soil types and concentrations, which paves the way for a variety of applications in the field.

Evaluation of constraints in bioremediation of weathered hydrocarbon-contaminated arid soils through microcosm biopile study

This research investigated the factors influencing bioremediation (biopile) of arid soils contaminated by weathered hydrocarbons. Five soils were thoroughly characterised to determine total petroleum hydrocarbons (TPH), their physicochemical properties and microbial diversity. Identified biopile-limiting factors are to be elevated petroleum hydrocarbon concentrations, high electrical conductivity and the magnitude of the recalcitrant hydrocarbon fraction. To optimise the biopile parameters, microcosm study was conducted which showed significant TPH reduction in three of five soils (BP-1, BP-2 and BP-4) but not in other two (BP-3 and BP-5), where BP-3 had a very high hydrocarbon concentration (123,757 mg kg−1) and BP-5 had a high proportion of recalcitrant hydrocarbons (>70 % of C29). Highest TPH removal (68 %) occurred in soil BP-2 and the lowest (5 %) in soil BP-3 over 56 days. Surfactant (Triton) addition, nutrient amendment or the soil dilution did not improve TPH degradation in soils BP-3 and BP-5. Phylogenetic analysis conducted during the remediation process found that hydrocarbon concentration and hydrocarbon fraction exerted the main effect on bacterial abundance, diversity and assemblage composition. At lower concentrations (~1000–4000 mg kg−1), bacterial diversity and abundance increased significantly, whilst decreased in higher concentrations. Although high TPH content and detection of TPH degraders, TPH biodegradation is limited in soil (BP-5) due to the presence of less soluble hydrocarbon fraction which indicated low TPH bioavailability (~7 %). Biopile could be applied as a technology to remediate three soils (BP-1, BP-2 and BP-4) but further modification of the biopile treatments required for other two soils BP-3 and BP-5.

경유 주입량과 토양 조성에 따른 유류 오염토양 내 TPH 측정 농도 변화 연구

This study investigated the effects of oil dose and soil texture on the analysis results for total petroleum hydrocarbon (TPH) in artificially oil-contaminated soils. The same amount of diesel was mixed with soils having different soil texture, and soil TPH concentrations were then analyzed for comparison. Presence of clay in the soil showed lower soil TPH analysis results than that of sand only. As the clay content was increased in the soil, the lower soil TPH concentration was obtained by incompleteness of solvent extraction. As the organic matter content in soil was increased from 5.2% to 10% (weight basis), a higher concentration of TPH was obtained by TPH analysis. However, at a higher organic content in the soil, 18%, resulted in a lower TPH concentration than those of 5.2% and 10%. Gasoline dose to the soil resulted in a significantly low TPH concentration due to the volatilization of gasoline while soil mixing and analysis. This study results would provide fundamental information either to the expectation of TPH concentration in artificially oil-contaminated soil or to estimation of oil release in the real oil-contaminated site.

Effects of Petroleum Hydrocarbon Contaminated Soil on Germination, Metabolism and Early Growth of Green Gram, Vigna radiata L.

The objective of the present study was to evaluate effects of petroleum hydrocarbon contaminated soil on the leguminous plant, Vigna radiata L. Seed germination, metabolism and early growth performance of V. radiata L. were studied as parameters by applying a combined approach. The employed combined method which included microcalorimetry and analysis of the root cross section revealed dose dependent effects of petroleum hydrocarbon contaminated soil on V. radiata L. for most parameters. Although significant reductions in measured parameters were observed even at low total petroleum hydrocarbon (TPH) levels such as 1% and 1.5%, calculated inhibitions, IC50 values and metabolic heat emission-time curves inferred that substantial negative effects can be expected on V. radiata L. in soils with comparatively high contamination levels, such as 2.5% TPH and higher.

Comparison of Attenuation of petroleum hydrocarbons in surface and subsurface soils amended with biostimulants

Two biostimulation treatments were compared in a laboratory incubation study with natural attenuation for total petroleum hydrocarbon (TPH) attenuation in gasoline and diesel spiked sandy soil at two different depths. One of the treatments was amended with 5 % clay which had pH of 6.9 and 6.98 and the other was amended with 3 % organic carbon with pH of 5.2 and 5.32 for both the surface and sub surface soils. At the end of 56 days of incubation, the soils amended with 5 % clay had no effect and those amended with organic carbon lost 69 % and 56 % of TPH for both the surface and subsurface soils respectively. These losses compared unfavourably with the non-amended soils with a pH of 7.57 and 7.92 which lost 78 % and 81 % of the TPH for both the surface and subsurface soils respectively. However, at days 0 – 14, the soils amended with 3 % organic carbon had the lowest concentrations of TPH which was attributed to sorption. These concentrations further changed at day 56 with the non amended soils now having the lowest TPH concentrations. 56 days after spiking with TPH, only the C 10 – C 12 and > C16 carbon number fractions were detected at both depths. Results suggest that natural attenuation can be a viable remediation strategy in soils with neutral to alkaline pH and that low pH of amendment material used could reduce TPH attenuation. Keywords: Petroleum hydrocarbons, pH, sorption, natural attenuation, clay, organic carbon Nigerian Journal of Technological Research

Germination, Survival, Growth Response of Eight Desert Plants to Oil Pollution and Removal Efficiency of Total Petroleum Hydrocarbon (TPHs)

The purpose of this study was to compare the effect of different concentrations of total petroleum hydrocarbon (TPHs) on plants in laboratory and the greenhouse, including seed germination, seeding survival, plant height, root length, biomass, and evaluate the removal efficiency of TPHs by 8 desert plants (Alhagi sparsifolia, Kalidium foliatum, Nitraria tangutorum, Lycium ruthenicum, Medicago sativa, Tamarix ramosissima, Suaeda altissima and Elaeagnus angustifolia). The results showed that seed germination response is not significant with all species in different treatments (0, 5, 10, 20 g/kg) but seedling survival was more sensitive than germination and all species could survived well in low TPHs contaminated soil. The seedling height, root length and their biomass of all tested plants were significantly reduced in higher concentration of TPHs contaminated soil. The average removal efficiency of TPHs by tested plants over the 120-day culture period was 56.1– 63.6%, 49.5–58.8% and 46.7–57.8% in different contamination concentration, when the removal rate by natural attenuation was 42.1, 41.8 and 37.6%, respectively. This indicated that all tested plants had a peculiar tolerance to petroleum contamination and could effectively degenerate TPHs. In addition, K. foliatum has the highest removal efficiency in 5 g/kg and 10 g/kg concentration of contamination soil. However, the removal efficiency of TPHs of L. ruthenicum in 20 g/kg concentration of contamination soil was higher than other species. Considering of growth and removal efficiency, L. ruthenicum, E. angustifolia and N. tangutorum, widely spread species in Xinjiang, can be effectively applied to phytoremediation of petroleum contaminated soil (≤20 g/kg).

Effect of Potassium Aluminium Sulphate, Kal(SO&lt;SUB&gt;4&lt;/SUB&gt;)&lt;SUB&gt;2&lt;/SUB&gt;on the Total Petroleum Hydrocarbon of Diesel Oil

Possible effects of the treatment of diesel oil with various concentrations of an inorganic salt, Potassium Aluminium Sulphate (KAl(SO<SUB>4</SUB>)<SUB>2</SUB>) were studied at room temperature, with a view to assessing alterations in the total petroleum hydrocarbon of diesel oil. Results obtained revealed that various concentrations of the inorganic salt had different effects on the total petroleum hydrocarbon (TPH) of the samples. The sample treated with 55g of the salt had the lowest TPH concentration of 2255.75mg/l while the sample treated with 35g of the salt had the highest TPH concentration of 12505.10mg/l. Two samples had higher TPH concentration than the untreated sample while five samples had lower TPH concentrations. This may be ascribed to the fact that some concentrations of the salt were able to catalytically crack heavier hydrocarbon molecules in the diesel oil to fractions lower than C6 (which may have been gases) thus leading to a decrease in the TPH concentration of those sample, while other concentrations of the salt were able to breakdown heavier hydrocarbon molecules to fractions within the C6 to C40 range thus leading to an increase in the TPH concentrations of the samples. The treatment also led to decrease and increase in the density of the samples.

Effects of petroleum contamination on soil microbial numbers, metabolic activity and urease activity

The influence of petroleum contamination on soil microbial activities was investigated in 13 soil samples from sites around an injection water well (Iw-1, 2, 3, 4) (total petroleum hydrocarbons (TPH): 7.5–78mgkg−1), an oil production well (Op-1, 2, 3, 4, 5) (TPH: 149-1110mgkg−1), and an oil spill accident well (Os-1, 2, 3, 4) (TPH: 4500–34600mgkg−1). The growth rate constant (μ) of glucose stimulated organisms, determined by microcalorimetry, was higher in Iw soil samples than in Op and Os samples. Total cultivable bacteria and fungi and urease activity also decreased with increasing concentration of TPH. Total heat produced demonstrated that TPH at concentrations less than about 1gkg−1 soil stimulated anaerobic respiration. A positive correlation between TPH and soil organic matter (OM) and stimulation of fungi–bacteria–urease at low TPH doses suggested that TPH is bound to soil OM and slowly metabolized in Iw soils during OM consumption. These methods can be used to evaluate the potential of polluted soils to carry out self-bioremediation by metabolizing TPH.