Crude Oil Contamination Research Articles

Phytoremediation of Light Crude Oil by Maize (Zea mays L.) Bio-Augmented with Plant Growth Promoting Bacteria

ABSTRACTThe aim of this study was to evaluate the converged effect of maize and plant growth promoting bacteria on degradation of petroleum hydrocarbons under axenic conditions. Artificially spiked sand with 10 g kg−1 light crude oil was planted with maize alone and in combination with eight bacterial isolates having plant growth promotion and bioremediation potential to observe the dissipation of petroleum hydrocarbons. Results showed remarkable suppression of maize growth and biomass production due to phytotoxicity of the crude oil contamination. However, bio-augmentation of plants with bacteria having ACC-deaminase activity significantly compensated the reduction in plant growth compared to uninoculated plants. The results revealed that plants bio-augmented with PM32Y exhibited significant increase in root length (75%), plant height (74%), and biomass (67%) as compared to uninoculated plants after 60 days of planting. The same bacterium in convergence with maize caused 43% degradation of petroleum hydrocarbons as compared to the unplanted and uninoculated control. Amplification, sequencing and phylogenetic analysis of 16S rRNA gene sequence identified PM32Y bacterium as Bacillus subtilis strain. It is concluded that bio-augmentation of plants with plant growth promoting bacteria having bioremediation potential and ACC-deaminase activity can successfully be used in phytoremediation of petroleum hydrocarbons.

Effect of oil-degrading bacteria on geotechnical properties of crude oil contaminated sand

Research Article| August 24, 2018 Effect of Oil-degrading Bacteria On Geotechnical Properties of Crude Oil–contaminated Sand Hossein Soltani-Jigheh; Hossein Soltani-Jigheh Department of Civil Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran Search for other works by this author on: GSW Google Scholar Hamed Vafaei Molamahmood; Hamed Vafaei Molamahmood Department of Civil Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran Search for other works by this author on: GSW Google Scholar Taghi Ebadi; Taghi Ebadi Faculty of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran Search for other works by this author on: GSW Google Scholar Ali Abolhasani Soorki Ali Abolhasani Soorki ACECR-Research Institute of Applied Sciences, Tehran, Iran Search for other works by this author on: GSW Google Scholar Environmental and Engineering Geoscience (2018) 24 (3): 333–341. https://doi.org/10.2113/EEG-1883 Article history first online: 25 Jul 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Hossein Soltani-Jigheh, Hamed Vafaei Molamahmood, Taghi Ebadi, Ali Abolhasani Soorki; Effect of Oil-degrading Bacteria On Geotechnical Properties of Crude Oil–contaminated Sand. Environmental and Engineering Geoscience 2018;; 24 (3): 333–341. doi: https://doi.org/10.2113/EEG-1883 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyEnvironmental and Engineering Geoscience Search Advanced Search Abstract Various materials have conventionally been utilized to improve the geotechnical properties of soils. Recently, utilization of microorganisms to this end has attracted much attention because of its high capabilities. Various oil-degrading bacteria have proven to be effective in degrading crude oil pollution from the soil. However, their effect on geotechnical properties of the soil has not been thoroughly investigated. In this research, various oil-degrading bacteria were employed to degrade crude oil contamination from crude oil–contaminated sandy soil. Then alterations on geotechnical properties of bio-treated sand were ascertained. The results showed that by employing these microorganisms, more than 50 and 80 percent of the crude oil was degraded after 10 and 30 days of bio-treatment, respectively. Moreover, bio-treated samples, which are slightly crude oil contaminated, acquire larger values of maximum dry density and cohesion in comparison to untreated contaminated samples. As treatment time increases, the value of the internal friction angle remains almost constant, and unconfined compression strength slightly increases. Generally, bio-treatment alters the geotechnical properties of the contaminated soil, and the application of bio-treated soil as a road basement in road construction and erosion controller is suggested. You do not currently have access to this article.

New naphthalene whole-cell bioreporter for measuring and assessing naphthalene in polycyclic aromatic hydrocarbons contaminated site

A new naphthalene bioreporter was designed and constructed in this work. A new vector, pWH1274_Nah, was constructed by the Gibson isothermal assembly fused with a 9 kb naphthalene-degrading gene nahAD (nahAa nahAb nahAc nahAd nahB nahF nahC nahQ nahE nahD) and cloned into Acinetobacter ADPWH_lux as the host, capable of responding to salicylate (the central metabolite of naphthalene). The ADPWH_Nah bioreporter could effectively metabolize naphthalene and evaluate the naphthalene in natural water and soil samples. This whole-cell bioreporter did not respond to other polycyclic aromatic hydrocarbons (PAHs; pyrene, anthracene, and phenanthrene) and demonstrated a positive response in the presence of 0.01 μM naphthalene, showing high specificity and sensitivity. The bioluminescent response was quantitatively measured after a 4 h exposure to naphthalene, and the model simulation further proved the naphthalene metabolism dynamics and the salicylate-activation mechanisms. The ADPWH_Nah bioreporter also achieved a rapid evaluation of the naphthalene in the PAH-contaminated site after chemical spill accidents, showing high consistency with chemical analysis. The engineered Acinetobacter variant had significant advantages in rapid naphthalene detection in the laboratory and potential in situ detection. The state-of-the-art concept of cloning PAHs-degrading pathway in salicylate bioreporter hosts led to the construction and assembly of high-throughput PAH bioreporter array, capable of crude oil contamination assessment and risk management.

Rapid Response of Eastern Mediterranean Deep Sea Microbial Communities to Oil

Deep marine oil spills like the Deepwater Horizon (DWH) in the Gulf of Mexico have the potential to drastically impact marine systems. Crude oil contamination in marine systems remains a concern, especially for countries around the Mediterranean Sea with off shore oil production. The goal of this study was to investigate the response of indigenous microbial communities to crude oil in the deep Eastern Mediterranean Sea (E. Med.) water column and to minimize potential bias associated with storage and shifts in microbial community structure from sample storage. 16S rRNA amplicon sequencing was combined with GeoChip metagenomic analysis to monitor the microbial community changes to the crude oil and dispersant in on-ship microcosms set up immediately after water collection. After 3 days of incubation at 14 °C, the microbial communities from two different water depths: 824 m and 1210 m became dominated by well-known oil degrading bacteria. The archaeal population and the overall microbial community diversity drastically decreased. Similarly, GeoChip metagenomic analysis revealed a tremendous enrichment of genes related to oil biodegradation, which was consistent with the results from the DWH oil spill. These results highlight a rapid microbial adaption to oil contamination in the deep E. Med., and indicate strong oil biodegradation potential.

Biomarkers of oxidative stress and health risk assessment of heavy metal contaminated aquatic and terrestrial organisms by oil extraction industry in Ogale, Nigeria

Ogale community in Rivers State, Nigeria is characterized by crude-oil contamination of its land resources. The present study aimed to evaluate the health risk and metal (Cd, Pb, Zn, Cr, and Ni) contamination level of the vegetable (Telfairia occidentalis), snail (Achatina achatina) and the catfish (Clarias gariepinus) collected from Ogale community. Samples collected from Elele Alimini community, a less polluted area was used as control. Oxidative damage was evaluated in tissues of snail and in the liver of catfish. The concentration of most of the tested metals in the food samples collected from the polluted sites were higher than those from the reference sites and in most cases exceeded the acceptable permissible limits. The accumulation of the metals by the food samples followed the order: T. occidentalis > A. achatina > C. gariepinus. The tissues of the snail from the polluted sites showed higher malondialdehyde (MDA) and lower glutathione (GSH) levels, and higher MDA and GSH levels in the fish liver compared to control values. The health risks associated with these metals in terms of dietary intake and target hazard quotients (THQs) showed higher non-carcinogenic effect and carcinogenic risks especially for Pb and Cd from the ingestion of Telfairia occidentalis and Achatina achatina from polluted sites. The health hazards due to metal pollution for the highly-exposed consumers of the food samples, especially in Ogale require attention. The oxidative stress response to accumulation status of metals provides a relevant tool for the assessment of metal pollution.

Effects of light crude oil contamination on small-strain shear modulus of Firoozkooh sand

The geotechnical properties of hydrocarbon-contaminated soils have been greatly concentrated so far due to its effectiveness and significance in various aspects of engineering applications. In this regard, several hydrocarbon contaminants and diverse soil types were considered in the literature aiming at evaluating physical, chemical and engineering characteristics of hydrocarbon-contaminated soils including particle size, hydraulic conductivity, compaction and compressibility, internal friction and cohesion as well as shear strength. Meanwhile, small-strain shear modulus of hydrocarbon-contaminated soils ( or ) has not been precisely focused. In this paper, bender element (BE) test was employed to examine the effects of a hydrocarbon (light crude oil) on shear wave velocity and the resultant of Iranian silica sand, Firoozkooh sand. In this connection, various methods of determining shear wave travel time in BE test were firstly evaluated, and the most reliable ones (start-to-start method and cross-correlation function) were employed to analyse the results. The values of were found highly sensitive to crude oil contamination and confining pressure so that increased after uniformly mixing oven-dried sand with 4 wt.% of crude oil under various confining pressure; however, the degree of induced changes diminished as confining pressure grew. Moreover, adding more crude oil up to 8 wt.% substantially decreased the value of to an amount slightly higher than that of the clean sand. Beyond this oil content (≥8 wt.%), followed a status of scattering and there was not significant alteration to be cited. The analytical results obtained by BE test about the hydrocarbon-induced alteration on could be confirmed by the microstructure observations via scanning electron microscopy.

Biomarkers of Aryl-hydrocarbon Receptor Activity in Gulf Killifish (Fundulus grandis) From Northern Gulf of Mexico Marshes Following the Deepwater Horizon Oil Spill.

Following the Deepwater Horizon oil spill, shorelines throughout the Barataria Basin of the northern Gulf of Mexico in Louisiana were heavily oiled for months with Macondo-252 oil, potentially impacting estuarine species. The Gulf killifish (Fundulus grandis) has been identified as a sentinel species for the study of site-specific effects of crude oil contamination on biological function. In November and December 2010, 4-5months after the Macondo well was plugged and new oil was no longer spilling into the Gulf waters, Gulf killifish were collected across the Barataria Basin from 14 sites with varying degrees of oiling. Fish collected from oiled sites exhibited biological indications of exposure to oil, including increase in cytochrome P4501A (CYP1A) mRNA transcript and protein abundances in liver tissues. Immunohistochemistry revealed increases in gill, head kidney, and intestinal CYP1A protein at heavily oiled sites. Intestinal CYP1A protein was a sensitive indicator of exposure, indicating that intestinal tissue plays a key role in biotransformation of AHR ligands and that ingestion is a probable route of exposure, warranting additional consideration in future studies.

Screening of Halophilic Bacteria Able to Degrade Crude Oil Contamination from Alborz Oil Field, Qom, Iran

Screening of Halophilic Bacteria Able to Degrade Crude Oil Contamination from Alborz Oil Field, Qom, Iran

Crude oil contamination of plastic and copper drinking water pipes

This study was conducted to determine the susceptibility of plastic (i.e., PEX, HDPE and CPVC) and copper pipes to short-term contamination by crude oil. Pipes were exposed to highly and slightly contaminated drinking water for the typical duration of Do Not Use drinking water orders. PEX pipes sorbed and desorbed the greatest amount of monoaromatic hydrocarbons (MAHs), whereas copper pipes were less susceptible to contamination. For benzene, toluene, ethylbenzene, and xylenes (BTEX) quantified in water, only benzene exceeded its health based maximum contaminant level (MCL). The MCL was exceeded for copper pipe on day 3, for CPVC pipe through day 9, and PEX and HDPE pipes through day 15. The BTEX compound concentration in water after the pipes were returned to service depended on the initial crude oil concentration, material type, and exposure duration. Total organic carbon (TOC) measurement was not helpful in detecting oil contaminated water. Except BTEX, trimethylbenzene isomers and a couple of polycyclic aromatic hydrocarbons (PAHs) with and without MCLs were also detected desorbing from PEX-A pipe. Oil contaminated water must be thoroughly characterized and pipe type will influence the ability of drinking water levels to return to safe limits.

Biosurfactant production by Mucor circinelloides on waste frying oil and possible uses in crude oil remediation.

Biosurfactants are biocompatible surface active agents which many microorganisms produce. This study investigated the production of biosurfactants by Mucor circinelloides. The effects of different factors on biosurfactant production, including carbon sources and concentrations, nitrogen sources, and iron (II) concentration, were studied and the optimum condition determined. Finally, the strain's ability to remove the crude oil and its relationship with biosurfactant production was evaluated. The results showed that M. circinelloides could reduce the surface tension of the culture medium to 26.6 mN/m and create a clear zone of 12.9 cm diameter in an oil-spreading test. The maximum surface tension reduction was recorded 3 days after incubation. The optimum condition for biosurfactant production was achieved in the presence of 8% waste frying oil as a carbon source, 2 g/L yeast extract as a nitrogen source, and 0.01 mM FeSO4. M. circinelloides could consume 8% waste frying oil in 5 days of incubation, and 87.6% crude oil in 12 days of incubation. A direct correlation was observed between oil degradation and surface tension reduction in the first 3 days of fungal growth. The results showed that the waste frying oil could be recommended as an inexpensive oily waste substance for biosurfactant production, and M. circinelloides could have the potential to treat waste frying oil. According to the results, the produced crude biosurfactant or fungal strain could be directly used for the mycoremediation of crude oil contamination in oil fields.

Aliphatic hydrocarbons and triterpenes of the Congo deep-sea fan

Hydrocarbons were analyzed in sediments from the Congo River deep-sea fan, from the Congo River, and in sinking particles collected by sediment traps 40m above the sediment. Studied sites encompassed three lobes of decreasing age of formation along the canyon: sites A, F and C and a another lobe system, disconnected from the active channel since 4 ka, Site E. Terrestrial long-chain odd n-alkanes were dominant in all sediments of the lobe system. Unsaturated terpenoids sourced by higher plants, such as gammacerene, lupene, ursene and oleanene, were also detected. At site C, characterized by high accumulation rates (10–20cmyr−1), the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations 10–17μggOC−1) evidenced recent terrestrial and phytoplanktonic remains reworked in anaerobic conditions. In these sediments, organic carbon-normalized concentrations of terrestrial alkanes and terpenoids were several fold higher than in the lobe sediments with lower accumulation rates (sites A and F), arguing for a more rapid degradation of terrestrial hydrocarbons than bulk organic carbon in the first steps of pre-diagenesis. Ample variations in the contributions of biomarkers from higher plants, ferns, bacteria and angiosperms, indicate an heterogeneous contribution of the soil and vegetation detritus delivered to the Congo lobe sediments. Lower concentrations in terrestrial hydrocarbons at site E, 45km away from the active canyon, indicated that river particles are still admixed to the dominant marine organic matter. Diploptene and hop-7(21)-ene have a dual origin, from terrestrial and marine microorganisms. Scatter in their relationship to gammacerene argues for a contribution of marine microorganisms, in addition to soils-sourced microorganisms. The close distribution patterns of diploptene, hop-21-ene, hop-7(21)ene and neohop-13(18)-ene is in line with the hypothesis of sequential clay-catalyzed isomerisation of bacterial hopenes. Terrestrial biomarker accumulation fluxes at site C are one order of magnitude higher than vertical pelagic flux, demonstrating the magnitude of the inputs delivered through turbiditic transport in the submarine canyon. Crude oil contamination was evidenced at the disconnected site E (UCM, C21 to C26 tricyclic diterpanes, CPI) and, in smaller amounts, in some sediments from sites A and C. It may be related to marine crude oil extraction and transport. A short-chain mode of alkanes with an even predominance is evidenced in sediments of the lobe complex and likely sources, crude oil, microorganisms and ferns, are discussed.

An Experimental Characterization of Shear Wave Velocity (Vs) in Clean and Hydrocarbon-Contaminated Sand

The characteristics of hydrocarbon-contaminated soils have been among major concerns of geotechnical engineers due to its significant frequency of event and also its influential consequences on our surroundings from various environmental and engineering viewpoints. Heretofore, the effects of diverse kinds of hydrocarbon contaminants on majority of geotechnical properties of fine- and coarse-grained soils such as grain size, hydraulic conductivity, plasticity, compressibility, internal friction, cohesion, and shear strength have been investigated. However, there has not been a concentrated research study examining shear wave velocity ( $${\text{V}}_{\text{s}}$$ ) of hydrocarbon-contaminated soils as an important geotechnical property of soil due to this fact that, in small/very small strain levels, the maximum shear modulus of soils ( $${\text{G}}_{ \hbox{max} }$$ ) can be determined using shear wave velocity ( $${\text{G}}_{ \hbox{max} } =\uprho{\text{V}}_{\text{s}}^{2}$$ ). This paper aims to investigate effects of hydrocarbon contamination on shear wave velocity of sandy soils by comparing shear wave velocities in identically prepared clean and contaminated samples. To this aim, an Iranian light crude oil, a standard type of silica sand (Ottawa sand), and a bender element apparatus were used to minutely measure shear wave velocity of clean and crude oil contaminated sand samples. Moreover, dry and quasi-moist tamping methods were employed in order to provide comparable clean and contaminated specimens (containing 4, 6, 8, 10, and 12 wt% of crude oil), respectively. Firstly, a comprehensive bender element (BE) and resonant column tests were conducted on the identically prepared clean sand samples at various amounts of frequency (2–20 kHz) and under various confining pressure (50–500 kPa) to find the best methods of accurately determining shear wave travel time in BE tests. Thereafter, BE tests were conducted to examine shear wave velocity in contaminated specimens. Based on the results, it was found that there was a critical value for crude oil content with the maximum shear wave velocity so that shear wave velocity of 4 wt% contaminated sand (Vs-4 wt%) was about 1.2 times higher than clean one (Vs-clean), and contrastingly adding further crude oil up to 6 wt% made a significant reduction in value of shear wave velocity to some extent that Vs-6 wt% was slightly lower than Vs-clean (Vs-6 wt% = 0.95–0.97Vs-clean). Moreover, adding more contaminant (8–12 wt%) into sand had negligible influences on shear wave velocity. In this paper, the effects of crude oil contamination on sand microstructure were also evaluated using scanning electron microscopy.

Coiled Plant Tendril Bioinspired Fabrication of Helical Porous Microfibers for Crude Oil Cleanup.

Fabrication of the helical fibers with sheath/core structure comprising 3D interconnected porous polystyrene (PS) and ductile polyvinylidene fluoride is inspired by coiled plant tendril. The key innovation point applied in this study is to produce a helical porous system based on sheath/core structure that can come into being a huge storage space in the sorption process for crude oil. More importantly, the mechanical properties confirm to have a more excellent improvement than that of the initial PS fibers, which make it become a possible candidate for the large‐area sorption and reuse of crude oil from the ocean or industry. The bioinspired fabricating strategy opens a significant avenue between the coaxial electrospinning and crude oil contamination cleanup. It is also expected that the unique structure can make it a promising candidate for applications in energy conversion, tissue engineering, and intelligent devices.

Assessment of bacterial diversity associated with crude oil-contaminated soil samples from Assam

In this study, we are reporting bacterial diversity in crude oil-contaminated soil of Assam, India. Integration of physiological community profiling, culture-dependent and culture-independent (metagenome) approaches, was employed to obtain a complete picture of the total bacterial diversity. Samples collected from 10 sites contaminated with crude oil ranging from 0.22 to 89.36% were analysed, and altogether 160 culturable bacteria were isolated (117 Gram-positive and 43 Gram-negative bacteria). Molecular identification showed the predominance of genera Lysinibacillus, Alcaligenes, Bacillus, Clostridium, Enterobacter and Pseudomonas. Conversely, denaturing gradient gel electrophoresis (DGGE) profiles of 16S rDNA phylotypes showed the predominance of Sphingomonas, Ralstonia, Sphingobium, Massilia, Acinetobacter and Pseudomonas. Both culture-dependent and culture-independent approaches resulted in 11 genera of which Bacillus and Pseudomonas were the key inhabitants creating most favourable bacterial milieu in the presence of crude oil contaminants. Metabolic fingerprints data depicted in PCA plot demonstrated that sites CTF-D-1 and Core-10 were most diverged. It was further confirmed that variations of bacterial species dominance in different sites were due to origin of hydrocarbon contamination. We here claim that the present findings is a first-hand report on combined physiological community profiling, culture-based and culture-independent approaches in assessing total bacterial diversity in crude oil-contaminated soil of Assam.

Did the Deepwater Horizon oil spill affect growth of Red Snapper in the Gulf of Mexico?

The explosion of the Deepwater Horizon (DWH) oil platform in 2010 released more than 200 million gallons of crude oil into the northern Gulf of Mexico (GoM). Elevated levels of carcinogenic polycyclic aromatic hydrocarbons (PAHs) were abundant in the upper water column throughout the event. Previous research suggests that PAHs may have negatively affected fishes in the northern GoM. Our objective was to test whether crude oil contamination from the DWH oil spill was correlated with changes in growth rates in adult Red Snapper, Lutjanus campechanus. We fit von Bertalanffy growth curves and back-calculated length-at-age using data collected from 2011–2013 during long-line surveys in the northern GoM and on the West Florida Shelf. No significant variation in von Bertalanffy growth parameters existed among the catch years; a combined-years model gave L∞, k, and t0 values of 82.91, 0.20, and 0.43, respectively. No significant difference existed between pre- (back-calculated) and post-DWH growth curves. However, annual widths of the fourth, fifth, and sixth increments (the dominant cohorts in the population) declined significantly post-DWH (2010–2012) by 13%, 15%, and 22%, respectively, and were significantly smaller than the mean width of each respective increment in pre-spill years (2006–2009). While the DWH event was related temporally to growth declines in the dominant adult age groups, other environmental factors (winds, temperature, and river discharge) may also affect growth. Accordingly, meridional (V) and zonal (U) winds, sea level height anomalies (a proxy for water temperature variation), and Mississippi River discharge were compared to increment widths but none of the factors were strongly correlated with variation in age-specific growth increments (maximum Pearson’s r=0.47). Therefore, we are unable to reject the hypothesis that the DWH resulted in growth rate declines as opposed to climatic variation.

Influence of sour oil on calcareous deposit nucleation

PurposeThe aim of this paper is to investigate the influence of sour crude oil contaminant on the calcareous scale deposition under cathodic protection of carbon steel in artificial seawater.Design/methodology/approachElectrochemical and surface characterizations are carried out using chronoamperometry, electrochemical impedance spectroscopy, scanning electron microscope/energy dispersive spectroscopy, X-Ray diffraction and Raman spectroscopy techniques.FindingsResults showed that sour oil limited the deposit nucleation regarding its volume concentrations. The inhibition mechanism was examined to be simultaneous acts of pH reduction and mackinawite formation beside minor physical adsorption of oil molecules on steel electrode.Originality/valueThere is no paper concerning the proposed subject, and the idea of this work is fully novel which is of great significance because of the consequences of disastrous oil spill phenomena on the integrity of exposed offshore facilities in terms of optimum protection against probable corrosion mechanisms.

“Effect of giant rat’s tail grass (<i>Sporobolus pyramidalis p.beauv</i>) on Total Petroleum Hydrocarbon (TPH) and Heavy metals content of crude oil polluted soils”

Soil contamination by crude oil has been an issue within the oil producing areas of the Niger Delta Nigeria and so, many remediation methods; including phytoremediation, the use of plants, have been adopted for the remediation of the affected soils. Such plants are expected to be safe and effective in the clean-up of hydrocarbons and heavy metals from oil polluted sites. Giant rat’s tail grass ( Sporobolus pyramidalis p.beauv ) is among the plants being proposed. This study therefore investigated in eight-weeks, the effects of giant rat’s tail grass ( Sporobolus pyramidalis p.beauv ) on the total petroleum hydrocarbon (TPH) and heavy metals content of contaminated soils. Residual TPH and heavy metals (chromium, Cr and lead, Pb) were quantified as an index for assessing the post-phytoremediated crude oil contaminated soils. Crude oil pollution levels of 25ml/kg, 50ml/kg and 100ml/kg on soils were respectively done alongside the unpolluted control. Remediation treatments of the test soils and the control with the plant were done after two weeks of pollution using three young seedlings of giant rat’s tail grass. Results from eight weeks remediation period showed that TPH (mg/kg) reduced from 496.55 to 257.90, 578.09 to 241.37, 602.61 to 198.80 and 21.27 to 6.22 on the test soils and the control respectively; Cr (mg/kg) from 5.86 to 1.23, 7.96 to 1.38, 9.76 to 1.65 and 4.26 to 0.63 on the test soils and the control respectively; and Pb (mg/kg) from 4.25 to 1.21, 5.26 to 2.31, 5.12 to 3.93 and 1.96 to 0.43 on the test soils and the control respectively. Soil analysis results from the study indicated that giant rat’s tail grass ( Sporobolus pyramidalis p.beauv ) has the potential to ameliorate crude oil toxicity at different crude oil contamination levels because of its ability to significantly (p>0.05) decrease the TPH and heavy metals content of the soil. Keywords : Total Petroleum Hydrocarbon, Heavy Metals, Phytoremediation, giant rat’s tail, crude oil contamination

The Dynamic Change of Microbial Communities in Crude Oil-Contaminated Soils from Oil Fields in China

ABSTRACTTo study the biodegradability of microbial communities in crude oil contamination, crude oil-contaminated soil samples from different areas of China were collected. Using polyphasic approach, this study explored the dynamic change of the microbial communities during natural accumulation in oil field and how the constructed bioremediation systems reshape the composition of microbial communities. The abundance of oil-degrading microbes was highest when oil content was 3–8%. This oil content is potentially optimal for oil degrading bacteria proliferation. During a ∼12 months natural accumulation, the quantity of oil-degrading microbes increased from 105 to 108 cells/g of soil. A typical sample of Liaohe (LH, oil-contaminated site near Liaohe River, Liaoning Province, China) was remediated for 50 days to investigate the dynamic change of microbial communities. The average FDA (a fluorescein diacetate approach) activities reached 0.25 abs/hr·g dry soil in the artificially enhanced repair system, 32% higher than the 0.19 abs/hr·g dry soil in natural circumstances. The abundance of oil-degrading microbes increased steadily from 0.001 to 0.068. During remediation treatment, oil content in the soil sample was reduced from 6.0% to 3.7%. GC–MS analysis indicated up to 67% utilization of C10–C20 normal paraffin hydrocarbons, the typical compounds that undergo microbial degradation.

Earthworms (Eisenia fetida) demonstrate potential for use in soil bioremediation by increasing the degradation rates of heavy crude oil hydrocarbons.

Crude oil contamination widely impacts soil as a result of release during oil and gas exploration and production activities. The success of bioremediation methods to meet remediation goals often depends on the composition of the crude oil, the soil, and microbial community. Earthworms may enhance bioremediation by mixing and aerating the soil, and exposing soil microorganisms to conditions in the earthworm gut that lead to increased activity. In this study, the common composting earthworm Eisenia fetida was tested for utility to improve remediation of oil-impacted soil. E. fetida survival in soil contaminated with two distinct crude oils was tested in an artificial (lab-mixed) sandy loam soil, and survival compared to that in the clean soil. Crude oil with a high fraction of light-weight hydrocarbons was more toxic to earthworms than the crude oil with a high proportion of heavy polyaromatic and aliphatic hydrocarbons. The heavier crude oil was added to soil to create a 30,000mg/kg crude oil impacted soil, and degradation in the presence of added earthworms and feed, feed alone, or no additions was monitored over time and compared. Earthworm feed was spread on top to test effectiveness of no mixing. TPH degradation rate for the earthworm treatments was ~90mg/day slowing by 200days to ~20mg/day, producing two phases of degradation. With feed alone, the rate was ~40mg/day, with signs of slowing after 500days. Both treatments reached the same end point concentrations, and exhibited faster degradation of aliphatic hydrocarbons <C21, but all fractions, including aromatics >C21, decreased. During these experiments, soils were moderately toxic during the first three months, then earthworms survived well, were active and reproduced with petroleum hydrocarbons present. This study demonstrated that earthworms accelerate bioremediation of crude oil in soils, including the degradation of the heaviest polyaromatic fractions.

Uptake of Total Petroleum Hydrocarbon (TPH) and Polycyclic Aromatic Hydrocarbons (PAHs) by Oryza sativa L. Grown in Soil Contaminated with Crude Oil.

The purpose of this study was to determine whether total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbons (PAHs) present in crude oil contaminated sites are transferred to roots, shoots and finally the grains of rice crops (Oryza sativa L.) grown in those sites. Soil was artificially contaminated with crude oil at concentrations of 0, 1000, 5000, 10,000, and 15,000mg/kg, followed by planting of rice seedlings. After harvest, TPH in plant samples were measured, and it was determined that the uptake of TPH by the plants gradually increased as the concentration of oil in soil increased. Further, from GC-MS analysis, it was observed that PAHs including naphthalene and phenanthrene bioaccumulated in rice plant parts. Vital physico-chemical properties of soil were also altered due to crude oil contamination. Our study revealed that rice plants grown in crude oil polluted sites can uptake TPH including PAHs, thus emphasising the importance of prior investigation of soil condition before cultivation of crops.