Petrogenic Hydrocarbons Research Articles

Biomarkers on Sediments in a Highly Saline Aquatic Ecosystem: Case of the Moknine Continental Sebkha (Eastern Tunisia)

Surficial sediments from 18 sites throughout Moknine sebkha, one of the largest urbanized sebkha in the sahel of tunisia, were analyzed for biomarkers ( n-alkanes, hopanes and steranes ) to track the origin of organic inputs. A distinct spatial distribution of aliphatic hydrocarbons in sediments was observed in Moknine sebkha which subdivide this environment in two area . The submerged area is characterized by high concentration of OC 1-4.9%, EOM 2%-49% CO, aliphatic hydrocarbons 1350 µg.kg-1to 3700 µg.kg-1sediment dry weight. Emerged area is characterized by low concentration (OC<1%, EOM<12%OC and F1<1200 µg.kg-1sediment dry weight. Several ratios (e.g. CPI, ACL, NAR, TAR, Pr/Ph…) were used to evaluate the possible sources of terrestrial-lacustrine inputs of these hydrocarbons in the sediments. The various origins of aliphatic hydrocarbons were generally biogenic, including both terrigenous and cyanobacteria. The source of contamination is not petroleum. , the predominance of biogenic in combination with petrogenic hydrocarbons was indicated by the biomarkers. αβ trishomohopane C33 indicate an anthropogenic contribution (wastewater) in two stations (treated domestic wastewater (ssm1-2) and untreate industrial wastewater ssm6). The presence of biogenic hopanes (17β(H), 21β(H)-hopanes) indicate the biogenic origin of organic matter in the Moknine sebkha. The UCM not indicate petrogenic origin but high activities of bacteria in highly saline system.

Compound-Specific δ13C of n-Alkanes: Clean-Up Methods Appraisal and Application to Recent Sediments of a Highly Contaminated Bay

Different clean-up methods to determine isotopic composition of n-alkanes were tested. Sources of organic matter in Guanabara Bay were re-examined through the δ13C of individual n-alkanes in surface sediment samples. The n-alkanes were efficiently isolated without significant losses of the compounds of interest. The δ13C of n-alkanes (n-C17 to n-C35) ranged between -34.0 and -26.4‰. More depleted δ13C values associated to higher carbon preference index (CPI > 4) suggest prevalence of biogenic n-alkanes from terrestrial origin in the inner stations influenced by inputs from mangrove areas. Small isotopic differences between odd and even-numbered chains and 13C-enrichment in long-chain homologues indicate a petrogenic hydrocarbons contribution. Higher concentrations of short-chain compounds associated to a more 13C-enriched total organic carbon (TOC) were found near the most intense sewage discharges. Results show that δ13C of n-alkanes can be applied to a highly degraded system as the Guanabara Bay and help improve the characterization of the organic matter.

Oil pollution in soils and sediments from the Northern Peruvian Amazon

Oil has been extracted from the Northern Peruvian Amazon for over four decades. However, few scientific studies have assessed the impacts of such activities in the environment and health of indigenous communities in the region. We have investigated the occurrence of petrogenic hydrocarbon pollution in soils and sediments from areas favoured as hunting or fishing grounds by local indigenous inhabitants. The study was conducted in one of the most productive oil blocks in Peru, located in the headwaters of the Amazon river. Soils and river sediments, in the vicinity of oil extraction and processing infrastructure, contained an oil pollution signature as attested by the occurrence of hopanes and steranes. Given the lack of any other significant source of oil pollution in the region, the sources of hydrocarbons are likely to be the activities of the oil industry in the oil block, from voluntary discharges or accidental spills. Spillage of produced water was commonplace until 2009. Moreover, petrogenic compounds were absent in control samples in sites far removed from any oil infrastructure in the oil block. Our findings suggest that wildlife and indigenous populations in this region of the Amazon are exposed to the ingestion of oil polluted soils and sediments. The data obtained supports previous claims that the local spillage of oil and produced waters in the water courses in the Corrientes and Pastaza basins could have eventually reached the main water course of the Amazon.

Characterization and ecological risk of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in sediments of Shadegan international wetland, the Persian Gulf

The distribution and sources of PAHs and n-alkanes were determined in the surface sediments from 202 locations in Shadegan international wetland with 537,700ha. The concentrations of total n-alkanes and PAHs ranged from 395.3 to 14933.46μgg−1dw and 593.74 to 53393.86ngg−1dw, respectively. Compared with other worldwide surveys, the concentration and contamination of sedimentary hydrocarbons were classified very high. A common petrogenic hydrocarbon source was strongly suggested in all sites by n-alkanes' profile with a Cmax at n-C20, Pr/Ph and CPI ratios<1 in all sites, and high percentage of UCM. Typical profile of petrogenic PAHs with alkyl-substituted naphthalenes and phenanthrenes predominance, various PAH ratios and multivariate analysis indicated that PAHs were mainly derived from petrogenic source. Naphthalene-derived compounds in all sites were significantly above their ERL, and adversely affected benthic biota. 92% of the sites had mean ERM values<0.1, indicating high ecological risk on the wildlife of the wetland.

Soil bioremediation approaches for petroleum hydrocarbon polluted environments.

Increasing industrialisation, continued population growth and heavy demand and reliance on petrochemical products have led to unprecedented economic growth and development. However, inevitably this dependence on fossil fuels has resulted in serious environmental issues over recent decades. The eco-toxicity and the potential health implications that petroleum hydrocarbons pose for both environmental and human health have led to increased interest in developing environmental biotechnology-based methodologies to detoxify environments impacted by petrogenic compounds. Different approaches have been applied for remediating polluted sites with petroleum derivatives. Bioremediation represents an environmentally sustainable and economical emerging technology for maximizing the metabolism of organic pollutants and minimizing the ecological effects of oil spills. Bioremediation relies on microbial metabolic activities in the presence of optimal ecological factors and necessary nutrients to transform organic pollutants such as petrogenic hydrocarbons. Although, biodegradation often takes longer than traditional remediation methods, the complete degradation of the contaminant is often accomplished. Hydrocarbon biodegradation in soil is determined by a number of environmental and biological factors varying from site to site such as the pH of the soil, temperature, oxygen availability and nutrient content, the growth and survival of hydrocarbon-degrading microbes and bioavailability of pollutants to microbial attack. In this review we have attempted to broaden the perspectives of scientists working in bioremediation. We focus on the most common bioremediation technologies currently used for soil remediation and the mechanisms underlying the degradation of petrogenic hydrocarbons by microorganisms.

Determination of volatile organic compounds including alcohols in refill fluids and cartridges of electronic cigarettes by headspace solid-phase micro extraction and gas chromatography-mass spectrometry.

An analytical method for the detection of 14 volatile organic compounds (VOCs) was developed to investigate VOCs in refill fluids and cartridges of electronic cigarettes (EC) using headspace solid-phase micro extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). In total, 14 VOCs were identified and quantified in 283 flavored liquids, 21 nicotine liquids, and 12 disposable cartridges. The detected concentration ranges of the VOCs are as follows: benzene (0.008-2.28mgL-1), toluene (0.006-0.687mgL-1), ethylbenzene (0.01-1.21mgL-1), m-xylene (0.002-1.13mgL-1), p-xylene (0.007-2.8mgL-1), o-xylene (0.004-2.27mgL-1), styrene (0.011-0.339mgL-1), ethyl acetate (0.3-669.9mgL-1), ethanol (16-38,742mgL-1), methanol (66-3375mgL-1), pyridine (0.077-99.7mgL-1), acetylpyrazine (0.077-147mgL-1), 2,3,5-trimethylpyrazine (0.008-96.8mgL-1), and octamethylcyclotetrasiloxane (0.1-57.2mgL-1). Benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene coexisted in samples, which may have originated from the use of petrogenic hydrocarbons as an extraction solvent for flavor and nicotine from natural plants. The maximum detected concentrations of benzene, methanol, and ethanol in liquid samples were found in quantities higher than their authorized maximum limits as residual solvents in pharmaceutical products.

Significance of GC/FT-IR and GC/MS in recognizing the sources of organic materials from sediments along the Suez Gulf Shoreline, Egypt

ABSTRACTThe present work aims to using the application of GC, GC/MS, UV, and FT/IR spectroscopy organic matters extracted from sedimentary hydrocarbons from six coastal stations located in the Gulf of Suez and proposed to evaluate hydrocarbons in the sediments. The results the origins of hydrocarbons are multiple sources from terrestrial inputs, biogenic, and pyrolytic. Abundance of vascular plant n C23– n C33 alkanes with a high odd-to-even predominance, pristane, and phytane beside nC29/nC17 ratios and the presence of biogenic hopanes indicate the predominance of biogenic in combination with petrogenic hydrocarbons. FT-IR spectroscopic analysis indicates high concentrations of aliphatic hydrocarbons as well as mono- and polynuclear aromatic hydrocarbons are useful tool in organic geochemistry studies. UV analysis for organic matters incorporated in sediments reveals that oil pollutants have considerable amounts of aromatic compounds.

Polynuclear Aromatic Hydrocarbons in Port Valdez Shrimp and Sediment.

Polynuclear aromatic hydrocarbons (PAHs) from oil were present in some shrimp from Port Valdez, site of a ballast water treatment facility at the Alyeska Alaska Marine Terminal (AMT). Low-level petrogenic PAH concentrations were generally restricted to shrimp eggs in the vicinity of the AMT and extended along the southern shore of Port Valdez to Anderson Bay. Eggs had greater lipid content than other tissues and thus were the most vulnerable biological compartment to hydrocarbon accumulation. Petrogenic hydrocarbons were not observed in shrimp muscle and cephalothoraxes; thus, these tissues do not pose a human health risk. Risk for children older than age 2 years and adults consuming eggs also was low except for two unusual samples (of 32), collected about 17 km west of the treatment facility. In general, PAH loads were consistent with local time series data in other species. We infer that the accumulation mechanism was dissolved uptake from water, consistent with passive sampler observations completed more than a decade earlier. Hydrocarbon levels in the majority of samples were below toxic thresholds. Total PAH accumulation was substantially greater in some pink shrimp than in other species, thus differences in habitat utilization (muddy vs. rocky substrate) are potentially important.Electronic supplementary materialThe online version of this article (doi:10.1007/s00244-016-0279-3) contains supplementary material, which is available to authorized users.

Efficiency and kinetics in treatment of wastewater from garages and residential oil spills using membrane bioreactor technology

This research focused on the biodegradation of petrogenic hydrocarbons in wastewater using membrane bioreactor technology. Industrial oily wastewater with mixed fractions of hydrocarbons was collected and continuously treated for 50 days. Membrane bioreactor (MBR) effluent samples were analyzed daily for both aliphatic and aromatic hydrocarbons using gas chromatography–mass spectrometry. Many other water quality parameters were also measured including chemical oxygen demand, dissolved oxygen, turbidity, heavy metals and heterotrophic bacterial counts. These parameters were essential in evaluating the performance of the MBR treatment process. During the treatment period, 98.0, 96.0 and 99.8 % removal of total aliphatic hydrocarbons in the lube oil fraction, total aliphatic hydrocarbons and total polycyclic aromatic hydrocarbons, respectively, were achieved. Overall, total organic removal, measured in terms of chemical oxygen demand, ranged from 88.3 to 92.6 %. Degradation kinetics was investigated for hydrocarbons and chemical oxygen demand. Half-lives of alkanes varied from several days to 40 days in the treatment process. Therefore, this study demonstrated that MBR is an effective treatment method for the removal of petroleum hydrocarbons in wastewater.

Monitoring of pollution in Egyptian Red Sea

The level of the Egyptian Red Sea water pollution by oil was studied to assess the general pattern of oil pollutants and to evaluate the hydrocarbon origin (anthropogenic, petrogenic or biogenic) with emphasis on the poly aromatic hydrocarbons in surface water. The oil extracted from the samples was analyzed by gas chromatography to determine the concentrations and distribution of aliphatic and alicyclic n-alkanes. Results obtained indicate that most of the organic species present in water samples consist of petrogenic hydrocarbons with additional biogenic types. High performance liquid chromatography (HPLC) technique was used to study the poly aromatic hydrocarbons (PAHs) fingerprints of the studied water samples. The results obtained indicate the presence of PAHs of both pyrogenic and petrogenic origins.

Assessment of soil organic contamination in a typical petrochemical industry park in China.

The concentrations of total petroleum hydrocarbons (TPH), n-alkanes (n-C8 through n-C40), and 16 polycyclic aromatic hydrocarbons (PAHs) in soils were determined to assess the level of organic contamination in soils from the Da-gang Petrochemical Industry Park with several big state-run enterprises, a recent rapid flourishing park in China. The results showed that the concentration of TPH in soil was high, up to 20 ng/g-12.8478%; in particular, the content in most sites ranged from 1 to 2%. Thus, it is clear that soil environment in the Da-gang Petrochemical Industry Park has been seriously polluted by TPH according to the Nemerow pollution index method. Furthermore, the average concentration of Σ(n-C>16 through n-C34) in 30 sampling sites was above the maximum limit set for F3 under all the conditions in the Canada-wide standards for petroleum hydrocarbons (PHC CWS) with 43.33-93.33% soil samples exceeding F3 standards, and n-alkanes possessing higher concentrations were proved much abundant alkanes in this study. Besides, the predominance of even n-alkanes and lower carbon preference index (CPI) demonstrated that n-alkanes in surface soils were mainly caused by anthropogenic inputs, while the concentration of Σ16-PAHs was in the range of 1652.5-8217.3 ng/g and the BaA/(BaA + Chr) and Flu/(Flu + Pyr) ratios indicated that pyrogenic PAHs may be the dominant PAHs in most soils with the contribution of petrogenic hydrocarbons in some sites.

Analysis of Laser-Induced Fluorescence Spectra Obtained in Spray Flames of Diesel and Rapeseed Methyl Ester Using the Multiple-Excitation Wavelength Laser-Induced Incandescence Technique with IR, UV, and Visible Excitations

Laser induced fluorescence (LIF) measurements have been performed in spray flames of diesel and rapeseed methyl ester (RME) using laser excitations of 266 nm, 355 nm, and 532 nm. Ultraviolet (UV) measurements in cold sprays of both fuels have also been carried out and are reported in this article. The LIF spectra obtained when exciting the cold spray of diesel with 266-nm and 355-nm laser excitations have been correlated to the presence of petrogenic polycyclic aromatic hydrocarbons (PAHs), which are known to be present in petroleum-derived fuels. Low fluorescence signals have also been detected for such excitation wavelengths in the RME spray. These signals have been related to the presence of trace species derived from the vegetable oil used to obtain the studied biodiesel. LIF signals obtained in flame conditions have been originally derived using a spectrally resolved multiple-excitation wavelength technique coupling laser-induced incandescence and fluorescence (LII/LIF). Such a technique is well adapted to isolate fluorescence emissions with a high signal/noise ratio in flame regions where soot and soot precursors coexist. A significant reduction of the LIF intensities has been observed for the three considered excitation wavelengths when using RME instead of diesel. The spectra obtained as a function of the height above the burner (HAB) with UV excitations are red-shifted in the diesel flame, while they exhibit the same spectral width in the RME one. This could be explained by the presence of other species in the RME flame, such as carbonyl compounds, that can interfere with the fluorescence of PAHs. LIF spectra at 532 nm present the same shape in both flames regardless of the HAB. Similar LIF spectra have also been obtained at specific positions in both flames with UV and visible excitations, which can be related to a similar distribution of PAHs. Thus, such a finding suggests that the heavy aromatic compounds that are related to the formation of nascent soot are similar despite the absence of petrogenic PAHs in RME.

Assessment of the Hydrocarbon Degrading Abilities of Three Bioaugmentation Agents for the Bioremediation of Crude Oil Tank Bottom Sludge Contaminated Libyan Soil

Bioremediation is a widely used environmental friendly treatment method for petrogenic hydrocarbon contaminated soils but its application to the treatment of crude oil tank bottom sludge (COTBS) contaminated soil is limited especially in Mediterranean countries such as Libya. Therefore in this study, the hydrocarbon degrading abilities of three bioaugmentation agents Pseudomonas sp (4M12), Pseudomonas xanthomarina (4M14) and Arthrobacter nitroguajacolicus (1B16A) (isolated from COTBS polluted soils) applied as part of a biostimulation-bioaugmentation (BS/BA) strategy were assessed in COTBS contaminated Libyan soils. Biostimulated (BS) and natural attenuation (NA) microcosms were also set up for comparative purposes. Gas chromatograph mass spectrometer (GC- MS) analysis revealed a total soil petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAHs) content of 30,703 mg kg-1 and 13,816 mg kg-1 respectively. Two carcinogenic fractions (naphthalene and benzenamine, 4, 4`methylenbis [2-methyl-]) and 4 mutagenic fractions (pyrene, phenanthrene, fluorene and anthracene) were detected. Substantial PAH degradation occurred in 4M14 and 4M12 samples within 15 days in contrast to up to 23 days in 1B16A, NA. However, substantial reduction in TPH (> 97%) was only observed in 4M12 and 4M14 inoculated microcosms within 15 days compared to 25-30 days in 1B16A inoculated, BS and NA microcosms. 4M14 inoculated microcosms were most efficient at complete removal (D100) of all carcinogenic and mutagenic fractions; 4M14 (9-10 days), 4M12 (9-15 days), 1B16A (15-23 days), BS (18-21 days) and NA (18-22 days). Pseudomonas xanthomarina was therefore shown as the best candidate for use in a BS/BA approach for treating COTBS contaminated Libyan soils. This study shows the importance of pre-screening bioaugmentation agents for the removal of carcinogenic and mutagenic fractions prior to use; in order to carry out safe, efficient and sustainable COTBS bioremediation in Libya.

Chemical fingerprinting of hydrocarbon-contamination in soil.

Chemical fingerprinting analyses of 29 hydrocarbon-contaminated soils were performed to assess the soil quality and determine the main contaminant sources. The results were compared to an assessment based on concentrations of the 16 priority polycyclic aromatic hydrocarbons pointed out by the U.S. Environmental Protection Agency (EPAPAH16) and total petroleum hydrocarbon (TPH). The chemical fingerprinting strategy proposed in this study included four tiers: (i) qualitative analysis of GC-FID chromatograms, (ii) comparison of the chemical composition of both un-substituted and alkyl-substituted polycyclic aromatic compounds (PACs), (iii) diagnostic ratios of selected PACs, and (iv) multivariate data analysis of sum-normalized PAC concentrations. The assessment criteria included quantitative analysis of 19 PACs and C1-C4 alkyl-substituted homologues of naphthalene, fluorene, dibenzothiophene, phenanthrene, pyrene, and chrysene; and 13 oxygenated polycyclic aromatic compounds (O-PACs). The chemical composition of un-substituted and alkyl-substituted PACs and visual interpretation of GC-FID chromatograms were in combination successful in differentiating pyrogenic and petrogenic hydrocarbon sources and in assessing weathering trends of hydrocarbon contamination in the soils. Multivariate data analysis of sum-normalized concentrations could as a stand-alone tool distinguish between hydrocarbon sources of petrogenic and pyrogenic origin, differentiate within petrogenic sources, and detect weathering trends. Diagnostic ratios of PACs were not successful for source identification of the heavily weathered hydrocarbon sources in the soils. The fingerprinting of contaminated soils revealed an underestimation of PACs in petrogenic contaminated soils when the assessment was based solely on EPAPAH16. As alkyl-substituted PACs are dominant in petrogenic sources, the evaluation of the total load of PACs based on EPAPAH16 was not representative. Likewise, the O-PACs are not represented in soil quality assessments based on EPAPAH16 and TPH. The ∑O-PACs ranged between <limit of detection (LOD) (0.03 mg kg(-1) (dw)) and 150.61 mg kg(-1) (dw). The pyrogenic contaminated soils contained considerable amount of O-PACs corresponding to between 6 and 18% of the ∑EPAPAH16.

Recovery and Characterization of Oil from Waste Crude Oil Tank Bottom Sludge from Azzawiya Oil Refinery in Libya

In this work we present the results of quantitative and qualitative analyses of oil obtained from crude oil tank bottom sludge (COTBS) generated from Azzawiya oil refinery in Libya. The aim of the study was to recover and evaluate oil from waste oily sludge and to compare it with parent oil (Hamada crude oil) in order to assess the commercial potential of recycling the oil. The benefits would be two-fold, firstly to improve oil utilisation efficiency and secondly in reducing the environmental contamination associated with the petrogenic hydrocarbon industry. Oily COTBS and extracted oil were characterised and key properties were measured including water and oil content, light and heavy hydrocarbon content, solid content and organic matter content for COTBS and water content, density, specific gravity, API (American Petroleum Institute) gravity, viscosity, salt and ash content for the extracted oil. Solvent (hexane) extraction confirmed that the oily sludge contained 42.08% (± 1.1%) oil composed of light hydrocarbons (30.7 ± 0.07%) and heavy hydrocarbon (69.3 ± 0.4%) fractions. The water and solid contents were 2.9% (± 0.2%) and 55.02% (± 0.6%) respectively. The properties of the recovered oil were assessed; gas chromatograph spectrophotometer (GC-MS) results indicated that the oil contained 139 different hydrocarbon fractions with a total petroleum hydrocarbon (TPH) concentration of 29,367 mgkg-1 and a polycyclic aromatic hydrocarbons (PAH) concentration of 11,752 mgkg-1. Several parameters of the oil were measured and compared to the parent oil (Hamada crude oil) including density, specific gravity, viscosity, salt and ash content. The API of the extracted oil (33.03) was lower than the parent oil (38.8) due to a reduced light hydrocarbon (LHC) content. TGAFTIR hyphenation shows both mass loss of hydrocarbons— low, medium and high molecular mass over a range of temperatures between 60°C and 450°C. crude oil extract exhibited a non-Newtonian behaviour (shear thinning) for the shear rate sweep between 10 and 500/s. dynamic shear rheology data showed that the extracted oil exhibit more like a solid than liquid. Overall the findings of the study confirmed that COTBD has a significant amount of oil similar in properties to Hamada crude oil. This large amount can be reclaimed and recycles. Depending on this essay, a commercial process could be performed which in parallel will reduce the environmental contamination with hydrocarbons.

Identification of unresolved complex mixtures (UCMs) of hydrocarbons in commercial fish oil supplements

Heightened awareness of the health benefits of fish oil consumption has led to a great increase in the number of fish oil supplements available to the consumer. Therefore manufacturers are continually looking for ways to distinguish their products from those of competitors. Minimally refined or virgin fish oils provide a unique feature; however, petroleum hydrocarbon contamination from oil spills is a reality in the world's oceans. The question arises whether oil produced from fish species caught in these polluted areas is free of petroleum hydrocarbons, with particular interest in unresolved complex mixtures (UCMs). This study investigates the presence of UCMs in commercially available fish oil supplements advertised as being virgin, as well as refined. Weathered petroleum hydrocarbons in the form of a UCM were found at 523 µg g(-1) in a virgin Alaskan salmon oil supplement. Supplements that were refined were free of this contamination. Fish used in the production of fish oil supplements appear to have accumulated petrogenic hydrocarbons in their tissues which were not removed by minimal oil refining. Further study is required to determine if there are any health implications associated with long-term consumption of these contaminated supplements.

Forensic source differentiation of petrogenic, pyrogenic, and biogenic hydrocarbons in Canadian oil sands environmental samples

To facilitate monitoring efforts, a forensic chemical fingerprinting methodology has been applied to characterize and differentiate pyrogenic (combustion derived) and biogenic (organism derived) hydrocarbons from petrogenic (petroleum derived) hydrocarbons in environmental samples from the Canadian oil sands region. Between 2009 and 2012, hundreds of oil sands environmental samples including water (snowmelt water, river water, and tailings pond water) and sediments (from river beds and tailings ponds) have been analyzed. These samples were taken from sites where assessments of wild fish health, invertebrate communities, toxicology and detailed chemistry are being conducted as part of the Canada-Alberta Joint Oil Sands Monitoring Plan (JOSMP). This study describes the distribution patterns and potential sources of PAHs from these integrated JOSMP study sites, and findings will be linked to responses in laboratory bioassays and in wild organisms collected from these same sites. It was determined that hydrocarbons in Athabasca River sediments and waters were most likely from four sources: (1) petrogenic heavy oil sands bitumen; (2) biogenic compounds; (3) petrogenic hydrocarbons of other lighter fuel oils; and (4) pyrogenic PAHs. PAHs and biomarkers detected in snowmelt water samples collected near mining operations imply that these materials are derived from oil sands particulates (from open pit mines, stacks and coke piles).

Evaluation of Total Petroleum Hydrocarbons (TPH) Measurement Methods for Assessing Oil Contamination in Soil

The most commonly used total petroleum hydrocarbons (TPH) analysis method measures petroleum hydrocarbon concentrations in soil by carbon range that can be detected by gas chromatography/flame ionization detection (GC/FID). Different cleanup procedures have been performed for removing some naturally occurring organics from petrogenic hydrocarbons prior to GC/FID analysis. To evaluate the different pre-treatment methods, more than 60 samples (including background soil and plant samples, as well as oil contaminated soil samples) were sampled from 2008 to 2010 in Canada. TPH values without cleanup (TPH-T), with column cleanup (TPH-F 3) and with in-situ cleanup (TPH-F) were compared to evaluate the effects of different pre-treatment methods on the TPH analysis values. Different total solvent extractable materials (TSEM) loading amounts were applied for in-situ silica gel cleanup method to evaluate the effect of the TSEM loading amount on the measured TPH-F values. The column cleanup method was evaluated by comparing the representative polar biogenic organic compounds (BOCs) and TPH in polar fraction (designated as TPH-F 4). Qualitatively, cleanup procedures removed most of the BOCs for background samples with high content of BOCs, but the GC/FID chromatograms did not show significant alteration for samples with heavy oil contamination. The quantified TPH-T, TPH-F 3 and TPH-F showed good agreement for oil contaminated samples, even though the loading dosage exceeded the maximum TSEM limits of silica gel (16.7 mg TSEM on per gram silica gel). For background samples, the measured TPH values were ranked as: TPH-T > TPH-F > TPH-F 3 when the TSEM loading amount exceeded 16.7 mg/g of silica gel, but no obvious difference was observed when the TSEM loading amount was less than 16.7 mg/g. Therefore, the TSEM loading capacity played an important role for the cleanup of background samples. The comparison of the measured TPH-T and TPH-F 3 obtained from background soil and plant samples did not show an obvious relationship, thus TPH values of soil samples can not be replaced by those from plants grown in the soil sampled area. The evaluation of column cleanup method showed that this method can effectively remove most of the BOCs, but the removal of the hydrocarbons which contribute to the measured TPH-F 3 can be negligible.

Tolerance of Selected Plant Species to Petrogenic Hydrocarbons and Effect of Plant Rhizosphere on the Microbial Removal of Hydrocarbons in Contaminated Soil

In this study, 11 plants (legumes, grasses, and crops) were screened for their ability to grow and survive in soil contaminated with 1 % diesel/oil mix (aliphatic hydrocarbons) or 1 % crude oil. Based on emergence, shoot length, root length, and root/shoot biomass ratio in contaminated soil, maize and wheat which showed the highest growth were selected for further investigation: a long-term phytoremediation study to evaluate the effect of maize and wheat on the microbial removal of hydrocarbons (1 % diesel/oil mix). The results showed that the presence of both maize and wheat in hydrocarbon-contaminated soil led to a significant increase in the utilization of total petroleum hydrocarbon (TPH), from 57 % in the control soil to 72 and 66 % in soil planted with maize and wheat, respectively. Microbial community analysis using denaturing gradient gel electrophoresis (DGGE) showed that the presence of a plant rhizosphere resulted in changes in the structure of the soil microbial community. Sequencing of prominent bands revealed the presence of a few hydrocarbonoclastic fungi only in the contaminated soil planted with maize and wheat. In terms of specific hydrocarbonoclastic activity, DGGE analysis based on alkB genes showed that soils with maize and wheat had similar rates of hydrocarbonoclastic activity but distinct microbial communities in some instances. Most probable number quantitative polymerase chain reaction (MPN-qPCR) confirmed that the number of alkB gene copies in soil planted with maize and wheat increased about 20- and 16-fold, respectively, relative to the control soil. This study showed that fungal and alkB bacterial communities contribute to the rhizoremediation of petrogenic hydrocarbons.

Plant residues — A low cost, effective bioremediation treatment for petrogenic hydrocarbon-contaminated soil

Petrogenic hydrocarbons represent the most commonly reported environmental contaminant in industrialised countries. In terms of remediating petrogenic contaminated hydrocarbons, finding sustainable non-invasive technologies represents an important goal. In this study, the effect of 4 types of plant residues on the bioremediation of aliphatic hydrocarbons was investigated in a 90day greenhouse experiment. The results showed that contaminated soil amended with different plant residues led to statistically significant increases in the utilisation rate of Total Petroleum Hydrocarbon (TPH) relative to control values. The maximum TPH reduction (up to 83% or 6800mgkg−1) occurred in soil mixed with pea straw, compared to a TPH reduction of 57% (4633mgkg−1) in control soil. A positive correlation (0.75) between TPH reduction rate and the population of hydrocarbon-utilising microorganisms was observed; a weaker correlation (0.68) was seen between TPH degradation and bacterial population, confirming that adding plant materials significantly enhanced both hydrocarbonoclastic and general microbial soil activities. Microbial community analysis using Denaturing Gradient Gel Electrophoresis (DGGE) showed that amending the contaminated soil with plant residues (e.g., pea straw) caused changes in the soil microbial structure, as observed using the Shannon diversity index; the diversity index increased in amended treatments, suggesting that microorganisms present on the dead biomass may become important members of the microbial community. In terms of specific hydrocarbonoclastic activity, the number of alkB gene copies in the soil microbial community increased about 300-fold when plant residues were added to contaminated soil. This study has shown that plant residues stimulate TPH degradation in contaminated soil through stimulation and perhaps addition to the pool of hydrocarbon-utilising microorganisms, resulting in a changed microbial structure and increased alkB gene copy numbers. These results suggest that pea straw in particular represents a low cost, effective treatment to enhance the remediation of aliphatic hydrocarbons in contaminated soils.