Oil Hydrocarbons Research Articles

Sepiolite promotes photodegradation of pyrene under visible light

Mechanochemistry and photocatalysis are emergent technologies for the remediation of polycyclic aromatic hydrocarbons (PAHs) in soils. In this work, mechanochemistry and photocatalysis are combined for pyrene degradation. The photodegradation of pyrene, when in contact with sepiolite under pressure application, is studied. The mechanical treatment leads to a pyrene crystal phase transformation. In this new phase, pyrene undergoes a fast photodegradation in the 320–420 nm range. We show that sepiolite is superior as a photocatalyst in pyrene degradation to TiO2, the most exploited photocatalyst. A broad physicochemical characterization is carried out to propose a mechanism in which the photoexcitation of mechanically altered pyrene leads to an electron transfer to sepiolite matrix, which triggers the PAH degradation. Finally, we want to highlight that the pyrene/sepiolite combination is a simplified system to shed light on how PAH photodegradation may occur in soils.

Radicals in West Absheron oil

Fractions of I-IV groups of aromatic hydrocarbons (AH) of West Absheron oil were studied by EPR and UV spectroscopy. Paramagnetism was not detected in the I group of AU. The presence of homologues of benzene, naphthalene, phenanthrene and anthracene was found in AC groups I-III. In oil fractions 120–230 oC, 150–280 oC EPR spectra are recorded ∆Hwidth=7.5 mT, g=2.3. Mn+2 were found in small amounts. In oil fractions 140–350 oC, 180–350 oC EPR signals were found ∆Hwidth=1.1 mT, g=2.002, which are also recorded in group II AC. Co, Mn+2 were also found in this group. In AC group IV, Co and asphaltene radicals are observed.

Spatial distribution and risk assessment of polycyclic aromatic hydrocarbons in soils from contaminated sites in Eastern China.

A total of 16 polycyclic aromatic hydrocarbons (PAHs) were measured in 28 soil column samples from two contaminated industrial sites in Eastern China. The total concentration of 16 PAHs (∑PAHs) in the surface soil (0-20cm) was measured up to 52,600ng/g (dry weight basis) with a remarkable spatial difference in the studied contaminated sites. The concentrations of the ∑PAHs in soils decreased with the increase in soil depth (0-10m). The surface and subsurface soil presented a tenfold higher concentration than the soil with depth greater than 4m. Additionally, the vertical migration tendency of the PAHs was found to be correlated significantly with their hydrophobicity (R2 = 0.79, P < 0.01). Naphthalene (with lowest octanol-water partition coefficient among the studied PAHs) showed the greatest average soil depth at which its peak concentration occurred. Furthermore, risk quotient analysis by using benzo[a]pyrene as reference compound showed that 71.4% of the samples exhibited high ecological risk for soil. Moreover, the total carcinogenic risk of the PAHs in the surface soil samples was assessed at 5.61 × 10-5-1.28 × 10-4 and 4.41 × 10-6-9.43 × 10-5 for male and female workers, respectively, in which 67.9%-71.4% of the samples showed potential risk. Generally, these results suggest a further consideration of ecological and health risks associated with PAHs in contaminated sites in Eastern China.

Application of whole-cell bioreporters for ecological risk assessment and bioremediation potential evaluation after a benzene exceedance accident in groundwater in Lanzhou, China

Oil spill events challenge human health and ecosystem safety, which are priority concerned issues for sustainable development. There is then an increasing demand of tools for ecological risks assessment at contaminated sites. In this study, we introduced two whole-cell bioreporters, ADPWH_alk and ADPWH_recA, to measure the available n-alkanes and the genotoxicities of total petroleum hydrocarbons in soils and groundwater which were contaminated by the Benzene Exceedance Accident in Lanzhou, China. Comparing to traditional chemical analysis methods, the whole-cell bioreporter method could provide risk assessment on cell level within a shorter time and a less cost, which is economical and environment friendly. The highest contents of available alkanes in soil and groundwater were 18,737 mg/kg and 308.4 mg/L, respectively. In addition, the available n-alkanes significantly (p < 0.01) correlated to chemical analysis of total n-alkanes. The highest genotoxicity level was found in soil and groundwater samples with lower TPHs concentration (4338.0 mg/kg and 1.4 mg/L Mitomycin C equivalent), suggesting the significant impacts of geochemical variables and alkane availability on the ecological risks of petroleum contamination. Combining chemical analysis and whole-cell bioreporter results, bioremediation strategies were suggested for groundwater and soils with higher n-alkane availability and lower ecological risks, whereas chemical oxidation were suggested for other contaminated sites. For the first time, we mapped the distribution of available n-alkanes and petroleum toxicities in a large scale soil-groundwater system using whole-cell bioreporters, showing their huge potential for rapid contaminant detection and fast risk assessment.

The impact of biochar-entrapped microorganisms on enzymatic activity and the cleanup of petroleum hydrocarbons in polluted soil

The impact of biochar-entrapped microorganisms on enzymatic activity and the cleanup of petroleum hydrocarbons in polluted soil

Evaluation of the content and degradation rates of PAHs in biochars, in terms of assessing the environmental risks of their application for soil remediation

The growing worldwide practice of biochar application as soil ameliorants, as well as adsorbents for remediation of soil contaminated with oil products and heavy metals, can lead to an increase the risk of environmental pollution by pyrolysis by-products. One of the most dangerous components of biochars is polycyclic aromatic hydrocarbons (PAHs), which are inevitably formed during the production of pyrogenic material. In this work, biochars obtained from various plant materials (millet, corn, willow, linden) under different pyrolysis temperatures were tested for the content of polycyclic aromatic hydrocarbons. The total content of PAHs in the studied samples ranged from 8.49 to 221.21 µg/kg, which does not exceed the limit concentrations established by the International Biochar Initiative. At the same time, polynuclear hydrocarbons with high carcinogenic and immunotoxic properties are found in the composition of biochars. A natural question arises about the effect of the final pyrolysis temperature on the total content and composition of PAHs in pyrolysis by-products. To study the degradation of polycyclic aromatic hydrocarbons in soil, linden biochar obtained by pyrolysis at 250 °C was used, from which the contaminants were extracted and applied to the soil so that the concentration of the marker was 20 and 40 µg/kg. The determination of the residual amount of polycyclic aromatic hydrocarbons was carried out after 1, 2, 6, and 11 months of incubation. Complete degradation of some 3–5-membered polycyclic aromatic hydrocarbons was found after 1–2 months of incubation. The most persistent pollutants were benzo(a)pyrene, benzo(b)fluoranthene, and pyrene, the concentration of which decreased to 31–71% on after 11 months of incubation. The slower degradation was found in the variant of the experiment with the high concentration level of polycyclic aromatic hydrocarbons. It was concluded that in soils selective accumulation of polynuclear PAHs, that most resistant to biodegradation, can occur.

In‐situ remediation of TPH‐polluted soil by Na2FeO4 in the Loess Plateau of China

AbstractIn recent years, the oil pollution problem on the Loess Plateau in western China is becoming increasingly serious, therefore, the use of hydroxyl radical (·OH) advanced oxidation process has increased due to its ability to efficiently degrade total petroleum hydrocarbon (TPH) in soil. However, the ability to produce ·OH of different oxidants varies widely, and the removal effect of specific pollutants has fluctuations and differences. The objective of this study is to screen the best oxidant according to the physico‐chemical properties and pollution situation of polluted soil, and to reveal the degradation mechanism of pollutants. In this study, we employed sodium ferrate (Na2FeO4) to produce ·OH for the degradation of TPHs in aged oil‐polluted soil located in the western part of the Loess Plateau in China. The results showed that the removal rates of TPH in the soil samples by hydrogen peroxide (H2O2), sodium persulfate (Na2SO4) and Na2FeO4 could reach 45.5%, 62.4%, and 65.6% respectively. The ·OH produced during the process played a major role in TPH oxidation with a contribution of more than 80%; H2O2 was intermediate substance that generated ·OH, biochar could induce the production of ·OH, the addition of biochar could activate H2O2 to promote the generation of ·OH and the removal rate is significantly increased by 19.2%. In situ remediation of polluted soil on the Loess Plateau using Na2FeO4, with a TPH degradation rate of 87.5%. The results of this study will provide a new method for the efficient degradation of TPH in loessial soil.

Hydrocarbon charging process of Ordovician strike‐slip fault zones in the Shunbei area, Tarim Basin, NW China

Ultra‐deep marine carbonate reservoirs is an important field for oil and gas exploration, and it is also a hot research topic in recent years. However, their hydrocarbon episodic charging model is still under debate up to now. A great breakthrough has been made in the newly discovered ultra‐deep fault‐karst oil reservoir in the Shunbei area of Tarim Basin. Based on quantitative gas chromatogram‐mass spectrometry, stable carbon isotopes of reservoir oils, microthermometry and confocal laser scanning analyses of fluid inclusions, the reservoir oil origin and hydrocarbon charging history in Shunbei No. 1, No. 5 and No. 7 strike‐slip fault zones are expounded. The results showed that the Ordovician reservoir oil derives from the source rocks within the Cambrian Yuertusi Formation deposited in a highly anoxic bottom water environment. There were four stages of hydrocarbon charging in the study area, in the late Caledonian, late Hercynian–Indosinian, middle Yanshanian and late Himalayan. During this period, the force‐field strength of the charged oil gradually decreased, and the early‐stage charged crude oil with low maturity and high force‐field strength preferentially accumulated in the Yijianfang Formation, while the late‐stage charged crude oil with high maturity and low force‐field strength preferentially accumulated in the Yingshan Formation. This study reveals the history and differences of petroleum accumulation in the Shunbei fault zones, which is significance for understanding the hydrocarbon distribution in ultra‐deep marine carbonate reservoirs.

Potential for natural attenuation of crude oil hydrocarbons in benthic microbiomes near coastal communities in Kivalliq, Nunavut, Canada

Oil spilled in marine environments can settle to the seafloor through aggregation and sedimentation processes. This has been predicted to be especially relevant in the Arctic due to plankton blooms initiated by melting sea ice. These conditions exist in the Kivalliq region in Nunavut, Canada, where elevated shipping traffic has increased the risk of accidental spills. Experimental microcosms combining surface sediment and crude oil were incubated at 4 °C over 21 weeks to evaluate the biodegradation potential of seabed microbiomes. Sediments sampled near the communities of Arviat and Chesterfield Inlet were assessed for biodegradation capabilities by combining hydrocarbon geochemistry with 16S rRNA gene and metagenomic sequencing, revealing decreased microbial diversity but enrichment of oil-degrading taxa. Alkane and aromatic hydrocarbon losses corresponded to detection of genes and genomes that encode enzymes for aerobic biodegradation of these compounds, pointing to the utility of marine microbiome surveys for predicting the fate of oil released into Arctic marine environments.

Artificial Olfactory System for Distinguishing Oil-Contaminated Soils

Oil-contaminated soils are a major environmental problem for Kazakhstan. Oil spills or leaks lead to profound changes in the physical and agrochemical properties of the soil and the accumulation of hazardous substances. Whilst there are many remote sensing techniques and complex laboratory methods for oil spill detection, developing simple, reliable, and inexpensive tools for detecting the presence of pollutants in the soil is a relevant research task. The study aims to research the possibilities of an electronic nose combining a chemical sensor array with pattern recognition techniques to distinguish volatile organic compounds from several types of hydrocarbon soil pollutants. An electronic nose system was assembled in our laboratory. It includes eight gas metal oxide sensors, a humidity and temperature sensor, an analog-digital processing unit, and a data communication unit. We measured changes in the electrical conductivity of sensors in the presence of volatile organic compounds released from oil and petroleum products and samples of contaminated and uncontaminated soils. The list of experimental samples includes six types of soils corresponding to different soil zones of Kazakhstan, crude oil from three oil fields in Kazakhstan, and five types of locally produced fuel oil (including gasoline, kerosene, diesel fuel, engine oil, and used engine oil). We used principal component analysis to statistically process multidimensional sensor data, feature extraction, and collect the volatile fingerprint dataset. Pattern recognition using machine learning algorithms made it possible to classify digital fingerprints of samples with an average accuracy of about 92%. The study results show that electronic nose sensors are sensitive to soil hydrocarbon content. The proposed approach based on machine olfaction is a fast, accurate, and inexpensive method for detecting oil spills and leaks, and it can complement remote sensing methods based on computer vision.

Оценка экологического состояния реки Сояна в зоне возможного воздействия алмазоносного месторождения

The article presents the results of a comprehensive study of the Soyana River for the first time. The characteristics of hydrological and hydrochemical parameters were obtained while observations in July 2020 and March 2021. Changes in the hydrogen index (pH), mineralization, and the content of dissolved oxygen and biogenic elements in water, as well as petroleum hydrocarbons in water and bottom sediments were studied using generally accepted in hydrochemical practice methods. The data obtained were evaluated for compliance with the regulatory requirements for the river water quality. According to the chemical composition, the Soyana River water belongs to the hydrocarbonate class of small and medium mineralization (164–296 mg/L), weakly acidic and slightly alkaline type (pH 6.0–8.2). The data obtained allow us to conclude that there is no noticeable anthropogenic impact on the considered watercourse. The petroleum hydrocarbons content in water and bottom sediments was below maximum permissible concentrations. In river water it was below 0.010 mg/L, in bottom sediments – in the range from 0.2 to 3.2 mg/kg. The maximum content of petroleum hydrocarbons in soils was recorded in the lower course of the river, where bottom sediments are presented in the form of silty sand. The interannual variability of hydrological and hydrochemical characteristics in the direction from the source to the mouth of the river is estimated. The relationship and regularity of their distribution was specified. The data obtained can serve as background data for assessing the negative impact in case of anthropogenic load on the river basin.

Source apportionment and source specific health risk assessment of HMs and PAHs in soils with an integrated framework in a typical cold agricultural region in China

A new innovative methodology system framework for source apportionment and source-specific risk assessment has been proposed and actively applied to identify the contamination characteristics, oriented sources and health risks associated with contamination levels of Heavy metals (HMs) and Polycyclic Aromatic Hydrocarbons (PAHs) in soils, a typical cold agricultural region in Northeastern China. To achieve this meaningful goal, a large-scale dataset including 1780 top soil samples, 10 HMs and 16 priority PAHs has been organized and collected from a typical study area in China. The total concentrations of the 10 selected HMs in study area range from 0.05 to 2147.40 mg/kg, with an average of 549.25 ± 541.37 mg/kg. The average concentrations of PAHs for (3–6)-rings are 16.60 ± 18.90, 26.40 ± 28.20, 9.51 ± 13.00 and 1.99 ± 5.30 ng/g, respectively. On the base of optimized literature source fingerprints for HM and PAH, a widely used receptor model, positive matrix factorization (PMF) has been applied to apportion the contamination sources HMs and PAHs in soils. Then source-specific health risk of soil HMs and PAHs have been assessed using the probabilistic incremental lifetime cancer risk model incorporated with source apportionment results data. Fertilizer residues/coke oven comprise the primary contamination source contributors of HMs and PAHs with corresponding contributions of 32.23 % and 27.93 % for HMs and 37.94 % for PAHs. Fertilizer/pesticide residues contributes most to the risks of soil HMs (28.8 %), followed by fossil fuel combustion (24.6 %), mining activities (20.2 %), traffic and vehicle emission (16.3 %) and electroplating/dyeing (14.1 %). Meanwhile, the ranking of health risks from the five identified contamination sources of soil PAHs are resident discharge, coal-fired boilers, coke oven emission, gasoline combustion and power plant, with the contribution of 27.1 %, 25.3 %, 17.3 %, 15.5 % and 14.8 %.And relatively, source-specific risk assessment demonstrates fossil fuel and coal combustion contribute the greatest impact to the total risk of HMs and PAHs (61.7 % and 56.1 %), respectively. This study provides a good example of how the source specific health risk assessment can be utilized to reduce the contamination in soils.

Pd nanoparticles lubricant additive catalyze the construction of carbon-based tribofilm to reduce graphitization-induced wear of DLC films under boundary lubrication

To explore approaches of reducing graphitization-induced wear on the friction surface of DLC films under boundary lubrication to increase their service life, Pd nanoparticles (PdNPs) prepared by chemical reduction method were used as lubricant additive of DLC films and GCr15 ball under boundary lubrication. Tribotests, reactive force field molecular dynamics (ReaxFF MD) and surface characterization methods, such as SEM, XPS, Raman and FIB-TEM, were used to study the effects of PdNPs as lubricant additive on the graphitization-induced wear of DLC films and the effect mechanisms. The results show that, PdNPs lubricant additive can reduce the friction coefficient (COF) of the tribosystems, and more importantly, they can obviously increase the lifespan of DLC films. Characterization results indicate that PdNPs can promote the tribochemical reaction on the friction surface and catalyze the formation of carbon-based tribofilm on the friction surface, which significantly reduces the graphitization-induced wear of DLC films. ReaxFF MD studies show that PdNPs effectively catalyze the massive dehydrogenation and chain-breaking of base oil hydrocarbon molecules, providing the basis for the formation of carbon-based tribofilm. These results indicate that PdNPs are promising as effective additive to prolong the service life of DLC films under boundary lubrication.

Screening of Bacteria Isolated from Arctic Atmospheric Aerosols for Oil Degradation Ability

Currently, a significant part of the world's soil cover is exposed to negative pollution, leading to its degradation. Oil hydrocarbons play a significant role among numerous soil pollutants. Sources of pollution are enterprises of oil extraction, oil refining, oil and oil products transportation. Every year in the world millions of tons of oil and oil products are lost during extraction, transportation, storage and use. Biological remediation based on the potential of microorganisms to transform pollutants of different origin is the most promising and environmentally safe method of restoring soil fertility, so the search for new strains to create and improve such biological preparations is still relevant. Atmospheric aerosols are a source of both transient and endogenous microbiota, which are metabolically active in relation to pollutants. During a complex airborne expedition on atmospheric sounding over the Arctic Ocean seas samples of aerosols were collected for microbiological analysis. The isolated cultures of microorganisms belonging to the genera Bacillus, Acinetobacter, Rhodococcus were tested for the ability to oil destruction when growing on agarized and liquid medium with the addition of oil to 2% as the only source of carbon and incubation for 10 days. The bioemulsifying and biodegrading abilities of microorganisms during growth in liquid medium were estimated visually by destruction of the surface film of oil, turbidity of the nutrient medium due to an increase in the biomass of microorganisms, formation of a uniform emulsion of oil in the medium, microscopy of cultural suspensions, and by their seeding on agarized nutrient medium to determine the titer of viable cells. Highly effective mesophilic and psychrotolerant oil destructor bacteria were isolated from northern atmospheric aerosols, which can be used to create complex biopreparations capable of assimilating a wider range of oil hydrocarbons for remediation of polluted soils and grounds in cold territories of Siberia and the Arctic.

Downwind gas condensate volatiles affect phytoplankton communities

We investigated the effects of volatile organic carbons (VOCs) evaporated from gas condensate on the cyanobacteria Synechococcus sp. WH8103, the diatom Asterionellopsis glacialis, and the dinoflagellate Alexandrium minutum. We used custom algal incubation chambers enabling only the gas condensate-derived VOCs to interact with the cell cultures via an atmospheric bridge, without direct contact with the hydrocarbon oil. The exposure to gas condensate VOCs reduced the abundance, growth rate, and photosynthetic efficiency of Synechococcus sp. WH8103. Thiobarbituric acid reactive substances (TBARS) assays hint at oxidative damage to the chloroplasts and/or the thylakoid membranes in this organism. A.glacialis abundance, physiological state and growth rates remained unchanged, whereas A.minutum abundance and photosynthetic efficiency increased relative to their respective controls. Our results demonstrate that the effects of a gas condensate formed due to an oil spill will not be restricted to the polluted area, but may be prominent in downwind locations through atmospheric transport.

Phytotoxicity of weathered petroleum hydrocarbons in soil to boreal plant species

Canada has extensive petroleum hydrocarbon (PHC) contamination in northern areas and the boreal forest region from historical oil and gas activities. Since the 2013 standardization of boreal forest species for plant toxicity testing in Canada, there has been a need to build the primary literature of the toxicity of weathered PHCs to these species. A series of toxicity experiments were carried out using fine-grained (<0.005–0.425 mm) background (100 total mg/kg total PHCs) and weathered contaminated soil (11,900 mg/kg total PHCs) collected from a contaminated site in northern Ontario, Canada. The PHC mixture in the contaminated site soil was characterized through Canadian Council of Ministers of the Environment Fractions, as indicated by the number equivalent normal straight-chain hydrocarbons (nC). The soil was highly contaminated with Fraction 2 (>nC10 to nC16) at 4790 mg/kg and Fraction 3 (>nC16 to nC34) at 4960 mg/kg. Five plant species (Elymus trachycaulus, Achillea millefolium, Picea mariana, Salix bebbiana, and Alnus viridis) were grown from seed in 0%, 25%, 50%, 75%, and 100% relative contamination mixtures of the PHC-contaminated and background soil from the site over 2–6 weeks. All five species showed significant inhibition in shoot length, shoot weight, root length, and/or root weight (Kruskal-Wallis Tests: p < 0.05, df = 4.0). Measurements of 25% inhibitory concentrations (IC25) following PHC toxicity experiments revealed that S. bebbiana was most significantly impaired by the PHC-contaminated soil (410–990 mg/kg total PHCs), where it showed <35% germination. This study indicates that natural weathering of Fraction 2- and Fraction 3-concentrated soil did not eliminate phytotoxicity to boreal plant species. Furthermore, it builds on the limited existing literature for toxicity of PHCs on boreal plants and supports site remediation to existing Canadian provincial PHC guidelines.

Measurement of polycyclic aromatic hydrocarbons in aroma-flavored olive oils produced using microwave and traditional maceration methods

Measurement of polycyclic aromatic hydrocarbons in aroma-flavored olive oils produced using microwave and traditional maceration methods

EVOLUTIONARY DEVELOPMENT OF MOTOR TRANSPORT DIESELS: ENVIRONMENTAL AND ECONOMIC INDICATORS

On the example of the most common in the use of diesel engines of commercial vehicles, the requirements for environmental and economic indicators, their evolutionary development over the past decades and, accordingly, changes in the impact on the environment and in the consumption of natural resources are considered. Road transport in terms of traffic significantly exceeds all other modes of transport, is the main consumer of scarce hydrocarbon oil fuels; and is considered the most significant pollutant of the surrounding atmosphere with toxic substances contained in the exhaust gases of engines.&#x0D; In recent years, during the development, implementation in production and use in operation, there have been significant changes in the design, technology, manufacturing, organization of the workflow, improvement of diesel engine systems that provide fuel and air supply, purification of exhaust gases from harmful emissions into the environment. The analysis of changes in requirements, the level of achieved economic and environmental performance of diesel engines of trucks, was carried out using the fuel-environmental criterion. The calculation data and the generalization of the results of the study made it possible to determine changes in the cost of fuel and compensation for environmental damage from the harmful effects of engine exhaust gases on the environment, related to a unit of power in operation, the coefficient of relative operating environmental costs, directly fuel-environmental criterion and to give a quantitative assessment of the evolutionary development of diesel engines of trucks. It has been established that the fuel and environmental efficiency of diesel engines of trucks over the past 30 years has increased by 4.17 times, mainly due to the reduction of harmful emissions into the environment with exhaust gases.

Accumulation and Toxicity of Polycyclic Aromatic Hydrocarbons in Long-Term Soil Irrigated with Treated Wastewater

Our study focuses on examining the effects of treated wastewater irrigation (TWWI) on agricultural soils in water-scarce regions, with a specific emphasis on the presence and accumulation of polycyclic aromatic hydrocarbons (PAHs). This issue is particularly significant due to its potential threats to environmental security. During our research, we discovered the existence of 16 different PAHs in these soils, which are known to have harmful impacts on ecosystems and human health. The concentration of total PAHs ranged from 163.9 ng g−1 to 9177.4 ng g−1, with 4- and 5-ring PAHs being the most dominant contributors. The PAHs Fluoranthene and Pyrene were found to be the most prevalent in all soil samples. Comparing the PAH concentrations in our research area to those reported in other studies, we observed that the agricultural areas in our study were more contaminated. Through positive matrix factorization (PMF) and diagnostic ratios (DRs) analyses, we identified petroleum combustion, vehicular emissions, as well as coal, grass, or wood combustion as the primary sources of PAH contamination. We also noted a negative correlation between clay, silt, pH, and PAH concentrations, while a significant positive relationship was observed between total organic carbon (TOC), sand, and PAHs. Based on the computed environmental risk index value, the presence of PAHs in the area poses a moderate to high level of ecological risk. TWWI was identified as the main contributor to PAHs in the agricultural soils we studied. Therefore, it is crucial to establish and enforce standards for wastewater reuse in agricultural fields before irrigation takes place.

Post Reclamation Evaluation of Residual Hydrocarbons in Crude Oil Contaminated Soil Using Gas Chromatographic Techniques and Plant Growth Indices

The present study was undertaken to evaluate the post-reclamation of crude oil-contaminated soil using gas chromatographic technique and plant growth indices. Enrichment techniques, turbidometric test, plasmid curing test, classical identification method, gas chromatographic flame ionization detection technique and plant growth indices were carried out using standard procedures. The results indicated that 22 of the isolates were observed to have high pollutant degrading potentials (A600nm &gt; 0.3) due to their crude oil utilization ability. The results also indicated that isolates which were able to degrade crude oil belonged to genera Bacillus, Pseudomanas sp., Ochrobacterium sp. and Enterobacter sp. Moreso, the remediation percentages recorded were 98 %, 80 %, 21 % and 98 %, 78 % and 22 % for the respective crude oil pollution (3 %, 5 % and 10 %) for soil inoculated plasmid borne bacteria whereas soil inoculated with plasmid cured bacterial cultures had 65 %, 52 %, 11 % and 65 %, 50 % and 20 % degradation of the same concentration of the total petroleum hydrocarbon after 60 days for both Phaseolus vulgaris and Glycine max plant seeds, respectively. The remediation percentages in the uninoculated controls include 3 %, 5 %, 10 % and 12 %, 9 % and 5 % across the pollutions for both plant seeds. A significant (P &lt; 0.05) increase in the growth parameters of the leguminous plants like percentage germination, mean plant shoot length, mean plant root length, plant fresh weight and number of root nodules were seen more in the soil microcosms inoculated with plasmid-borne bacteria than microcosm inoculated with culture of plasmid cured bacteria across all crude oil dilutions. Crude oil had a dose-dependent negative effect on the mean bacterial counts of each of the polluted soil containing the two different plants. Thus, the study clearly suggests that the selected hydrocarbon bacterial degraders could be effectively exploited in the remediation of crude oil-polluted sites.