Construction of an effective method combining in situ capping with electric field-enhanced biodegradation for treating PAH-contaminated soil at abandoned coking sites.

The simultaneous application of in situ capping and electro-enhanced biodegradation may be a suitable method for ensuring the feasibility and safety of reusing abandoned coking sites. However, the capping layer type and applied electric field pattern may affect the efficiency of sequestering and removing pollutants. This study investigated changes in electric current, soil moisture content and pH, polycyclic aromatic hydrocarbon (PAH) concentration, bacterial number, and microbial community structure and metabolic function during soil remediation at abandoned coking plant sites under different applied electric field patterns and barrier types. The results indicated that polarity-reversal electric field was more conducive to maintaining electric current, soil properties, resulting in higher microbial number, community diversity, and functional gene abundance. At 21d, the mean PAH concentrations in contaminated soil, the capping layer's clean soil and barrier were 78.79, 7.56, and 1.57 mg kg-1 lower than those with a unidirectional electric field, respectively. The mean degradation rate of PAHs in the bio-barrier was 10.12 % higher than that in the C-Fe barrier. In the experiment combining a polarity-reversal electric field and a bio-barrier, the mean PAH concentrations in contaminated soil and the capping layer were 706.68 and 27.15 mg kg-1 lower than those in other experiments, respectively, and no PAHs were detected in the clean soil, demonstrating that the combination of the polarity-reversal electric field and the bio-barrier was effective in treating soil at abandoned coking plant sites. The established method of combining in situ capping with electro-enhanced biodegradation will provide technical support for the treatment and reuse of heavily PAH-contaminated soil at abandoned coking plant sites.

Effects of soil organic carbon metabolism on electro-bioremediation of petroleum-contaminated soil.

Soil organic carbon (SOC) potentially interacts with microbial metabolism and may affect the degradation of petroleum-derived carbon (PDC) in the electro-bioremediation of petroleum-contaminated soil. This study evaluated the interactions among organic carbon, soil properties, and microbial communities to explore the role of SOC during the electro-bioremediation process. The results showed that petroleum degradation exerted superposition and synergistic electrokinetic and bioremediation effects, as exemplified by the EB and EB-PR tests, owing to the maintenance and enhancement of SOC utilization (P/S value), respectively. The highest P/S value (2.0-2.4) was found in the electrochemical oxidation zone due to low SOC consumption. In the biological oxidation zones, electric stimulation enhanced the degradation of PDC and SOC, with higher average P/S values than those of the Bio test. Soil pH, Eh, inorganic ions, and bioavailable petroleum fractions were the main factors reshaping the microbial communities. SOC metabolism effectively buffered the stress of environmental factors and pollutants while maintaining functional bacterial abundance, microbial alpha diversity, and community similarity, thus saving the weakened PDC biodegradation efficiency in the EB and EB-PR tests. The study of the effect of SOC metabolism on petroleum biodegradation contributes to the development of sustainable low-carbon electro-bioremediation technology.

Effects of thermal desorption on ecotoxicological characteristics of heavy petroleum-contaminated soil.

This study comprehensively evaluates the ecotoxicity of high-concentration heavy petroleum (HCHP)-contaminated soil before and after thermal desorption (TD) remediation at different temperatures and times. The results showed that the detoxification of contaminated soil was effectively achieved by extending the remediation duration at 400-600 °C. After treatment at 400 °C for 60 min, the toxicological indicators including bioluminescence EC50 (acute toxicity), seed germination ratio (Gr) and plant biomass of Brassica juncea (subacute toxicity), and diversity of the microbial community (chronic toxicity) reached a maximum. The value of the SOS-Induction Factor (SOSIF), characterizing genotoxicity was below 1.5, indicating that it was non-toxic. Pearson's correlation analysis illustrated that the water-soluble fraction (WSF), ALK1-3 and ARO1-3 of petroleum hydrocarbons were the primary sources of ecotoxicity. Notably, although the total ratio of petroleum removed from the soil reached 87.26 ± 4.38 %-98.69 ± 1.61 % under high-temperature thermal desorption (HTTD, 500-600 °C), the ecotoxicity was not lower than that at 400 °C. The pyrolysis products of petroleum macromolecules and extreme changes in soil properties were the leading causes of soil ecotoxicity following HTTD. The inconsistency between the removal of petroleum pollutants and ecological health risks reveals the significance of soil ecotoxicological assessments for identifying TD remediation endpoints and process optimization.

Highly efficient screening and optimal combination of functional isolates for bioremediation of hydrocarbon-polluted soil.

The key to enhancing the efficacy of bioremediation of hydrocarbon-contaminated soil is the precise and highly efficient screening of functional isolates. Low screening effectiveness, narrow screening range and an unstable structure of the constructed microflora during bioremediation are the shortcomings of the traditional shaking culture (TSC) method. To improve the secondary screening of isolates and microflora implemented for alkane degradation, this work evaluated the characterization relationship between bacterial function and enzyme activity and devised an enzyme activity assay (EAA) method. The results indicated a substantial positive correlation (r = 0.97) between 24 candidate isolates and their whole enzymes, proving that whole enzyme activity properly reflects the metabolic functions of microorganisms. The functional analysis of the isolates demonstrated that the EAA method in conjunction with microbial abundance and metabolite determination could broaden the screening range of functional isolates, including aliphatic acid-metabolizing isolates (isolates H4 and H7) and aliphatic acid-sensitive isolates (isolate H2) with n-hexadecane degradation ability. The EAA method also guided the construction of functional microflora and optimized the mode of application using combinations of alkane-degrading bacteria and aliphatic acid-degrading bacteria successively (e.g., F1+H7+H7). The combinations maintained a high abundance of functional isolates and stable α diversity and community composition throughout the experiment, which contributed to more advanced alkane degradation and mineralization ability (p < 0.01). Assuming a workload of 100 tests, the screening efficiency of the EAA method is more than 16 times that of the TSC method, and the greater the quantity of isolates, the higher the screening efficiency, enabling high-throughput screening. In conclusion, the EAA method has a broad-spectrum, accurate and highly efficient screening ability for functional isolates and microflora, which can provide intensive technical support for the development of bioremediation materials and the application of bioremediation technology.

Effects of mineral species and petroleum components on thermal desorption behavior of petroleum-contaminated soil.

Thermal desorption (TD) behavior of high-concentration petroleum-contaminated soil (PCS) is affected by soil composition, especially inorganic minerals. In this study, the TD behavior of petroleum-contaminated quartz (original mineral) and kaoline (clay mineral) were compared with those of pure petroleum (Petro-free); their "saturate, aromatic, resin, and asphaltenes" (SARA) fractions were investigated using thermogravimetry and differential thermogravimetry (TG-DTG). The modelling of the petroleum removal kinetics was also analyzed to provide insights into the mechanism. The results revealed that the limiting factor controlling the desorption of petroleum from quartz (Petro-Qtz) and kaoline (Petro-Kln) is the minerals, which increased the effective TD temperature by 200 °C and decreased TD efficiency by 2%. Compared to Petro-Qtz, Petro-Kln showed a lower desorption efficiency of 5% and the process was accomplished at a higher temperature of 100 °C. The investigation on SARA fractions indicated that polar fractions (i.e., aromatics, resins, and asphaltenes) were strongly captured by the minerals. The increment of the TD temperature of petroleum (resins-160 °C > aromatics-20 °C > saturates-5 °C) increased with the polarity of petroleum components. These results could be validated by thermogravimetry-gas chromatography/mass spectroscopy (TG-GC/MS) through the delayed desorption of naphthalene and acenaphthene. Furthermore, the increment of the TD temperature of SARA fractions on kaoline was higher than those on quartz. This makes sense because the kaoline decreased the diffusion of hydrocarbons due to its porosity features and higher specific surface area (kaoline 5.3300 m2 g-1, quartz 0.1153 m2 g-1). In addition, the analysis of the desorption kinetic models showed that the observed hysteresis was related to the diffusion barrier caused by chemisorption (n＜1). In consequence, the Petro-Kln showed a lower desorption efficiency, a slower desorption, and as a result, a higher energy consumption (0.476 kW h) for thermal remediation than Petro-Qtz (0.238 kW h).

Spatial variation of residual total petroleum hydrocarbons and ecological risk in oilfield soils.

Total petroleum hydrocarbon (TPH) pollution in oilfield soils is a worldwide environmental problem. In this study, we analysed the spatial variation of residual TPH components and the ecological risk they pose. The soils of five selected oilfields in China, across 11 degrees of latitude and 17 degrees of longitude were selected for the investigation. The results showed that the non-zonal composition of the residual TPHs in the soil was similar to the that of the crude oil input. Principal component analysis (PCA) suggested that the effect of zonal environmental factors explained 81.5% of the variability in the residual indexes of saturated and aromatic hydrocarbons. The first principal component, the soil clay and organic matter, correlated positively with the residual TPH index. The second principal component, the accumulated temperature, however, correlated negatively with the residual TPH index in the soil. Moreover, the application of the soil quality index (SoQI) and a Monte Carlo simulation for estimating the residual TPH content suggested that the ecological risk caused by residual TPHs in the soil decreased when the oilfield latitude and clay and organic matter content in the oilfield soil were lower. This study provides a basis for the assessment and monitoring of ecological risk in oilfield soils worldwide.

Spatial ecological risk assessment for contaminated soil in oiled fields.

Soil total petroleum hydrocarbon (TPH) pollution in oil fields is a worldwide environmental problem. In particular, the dense distribution of oil wells in low-permeability oil reservoirs has caused regional pollution superposition. We proposed a feasible method for the spatial ecological assessment for soil pollution in oil fields. Typical TPH-contaminated soil in the Shengli oil field was examined according to the classification of oil well properties, including the spatial structure, distribution density, and exploitation history. Soil TPH concentrations of each oil filed site was calculated by Monte Carlo simulation. The risks were assessed according to multiple receptors and risk sources. The results indicated that the average TPH concentration was greater than 2100 mg·kg-1. The differences of TPH concentrations were mainly correlated to the exploitation period. The soil TPH content demonstrated a spatial cluster pattern according to the Anselin Local Moran's Index (p < 0.01). The risk for wheat and earthworms showed that more than 98% of the study area was under a low risk level. However, high risk accounted for only 0.9% when bacteria was used as a bioindicator, and the composition of different risk levels was similar to that of the ecological risk assessed based on the soil quality index.

Assessment of the human health risk of polycyclic aromatic hydrocarbons in soils from areas of crude oil exploitation.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous carcinogenic pollutants. Areas where crude oil has been exploited are at risk due to PAHs from both natural and anthropogenic sources. The Shengli Oilfield in China was used to assess the health risk posed by PAHs in areas with different population densities. A risk assessment showed that in the areas with low, median, and high population densities, the probabilities of the total carcinogenic risk (TCR) exceeding 10-6 for adults were 9.9%, 9.3%, and 13.4%, respectively, whereas these were 7.8%, 7.1%, and 10.1%, respectively, for children. Crude oil, traffic, and residential emissions were the major sources of PAHs based on a factor analysis with a nonnegative constraint analysis. Crude oil sources accounted for 96.1% of the TCR in the low population area, whereas traffic accounted for 94.4% of the TCR in the high population area. Based on the national action plan, guidelines, and new standard for soil pollution control promulgated by the Chinese government, we assumed a reduced rate of soil PAHs from different sources, and the carcinogenic risk from PAHs in the area of crude oil exploitation could be forecast. The average probabilities of the TCR exceeding 10-6 for adults and children could be reduced by 45.8% and 49.4%, respectively, in 2040 relative to current values under a pollution control scenario. These findings highlight that the risks associated with soil contamination could be effectively controlled by implementing control policies.

Characteristics of organic carbon metabolism and bioremediation of petroleum-contaminated soil by a mesophilic aerobic biopile system.

An innovative mesophilic aerobic biopile technology was explored to improve the bioremediation efficiency of petroleum-contaminated soil. Under the suitable soil conditions (C:N:P at 100:5:1 and soil moisture content at 18%), the soil pH was hold in the range of 7.4 to 6.8 throughout the bioremediation process, the mesophilic (30 °C-40 °C) and forced aeration (3 h-on/1 h-off) conditions were the critical factors to enhancing petroleum biodegradation. The consumption of bioavailable organic carbon (BAC) which was one of the most important factors regulating microbial metabolism, was positively related (R2 = 0.85, 40 °C) with the rate of petroleum removal. The 50% threshold of BAC could be regarded as the signal for supplementing the soil nutrients in the mesophilic aerobic biopiles to favor petroleum removal. The optimal conditions (40 °C, 3 h-on/1 h-off) maximized the utilization of BAC, promoted the petroleum degradation, and remained the microbial abundance and community composition stable to the greatest extent. In addition, the accumulation of aliphatic acids affected the microbial activity, which limited the efficiency of petroleum degradation to a certain extent. Jointly considering the energy consumption, time cost and soil conditions maintenance, a cost-effective biopile technology was obtained by temperature and aeration regulation and BAC supplementation, which could be applied to engineering application.

Change in soil ion content and soil water-holding capacity during electro-bioremediation of petroleum contaminated saline soil.

This study investigated changes in soil ion content and soil water-holding capacity during electro-bioremediation (EK-Bio) of petroleum contaminated saline soil (ion content of 3.92 g/kg). The results indicated that the soil ions surrounded the electrodes with increasing time, thus changing the soil water-holding capacity. According to the Van Genuchten model fitting results, the soil residual water content (θr) increased with the soil ion content, which represented a capacity decrease of the soil water supply. At the end of the EK-Bio experiment, the θr values in the soil near (site A) and far from (site B) the electrodes were 19.1 % and 12.1 %, where the soil ion content was 7.92 g/kg and 0.55 g/kg, respectively. The ion aggregation process significantly impacted the growth of soil microbial. The bacteria numbers decreased when the soil ion content was high (7.41 g/kg, site A) and low (0.84 g/kg, site B) after 70 days of treatment. The applied electric field significantly enhanced the bioremediation efficiency. However, the biodegradation promotion effect was the weakest at site A. The synergistic effect between the applied electric field and degrading bacteria was delayed.

[Petroleum pollution and microbial community structure in the soil of Liaohe Oilfield.] / è¾½æ²³æ²¹ç”°åœŸå£¤çŸ³æ²¹æ±¡æŸ“åŠå ¶å¾®ç”Ÿç‰©ç¾¤è½ç‰¹å¾.

We analyzed the soil physico-chemcial properties, microbial community structure, petroleum hydrocarbon contents and components in soil samples from the well sites of Shuguang, Huanxi-ling and Jinzhou oil exploitation sites in Liaohe Oilfield, with uncontaminated paddy soil as a control. The results showed that: 1) The soil around all the three oil exploitation sites were seriously polluted by petroleum with certain differences in the petroleum hydrocarbon contents and components. The average content of petroleum hydrocarbon in the soil of Shuguang and Huanxiling oil exploitation sites was two times higher than that of Jinzhou oil exploitation site. The content of resins and asphaltenes in the soil of Shuguang oil exploitation site was the highest, while the soils of Huan-xiling and Jinzhou oil exploitation sites had the highest alkane content, which accounting for more than 40% in all the sites. 2)Compared with the paddy soil, the microbial OTU numbers, Chao1 and Shannon indices in the soil of Jinzhou oil exploitation site increased. The dominant phyla and genera were similar in the soil of all oil exploitation sites but with large differences in abundance. The soil in Jinzhou oil exploitation site had higher abundance of Mycobacterium and Pseudomonas, while Sphingomonas and Nocardioides, Massilia in the soil of Shuguang oil exploitation site, and Lysobacter, Thiobacillus and Pseudomonas in the soil of Huanxiling oil exploitation site. 3) The abundances of Sphingomonas, Nocardioides, Thiobacillus, Massilia, Pseudomonas and the contents of total petroleum hydrocarbons, total organic carbon and resins and asphaltenes were significantly positively correlated, while Mycobacterium, Lysobacter and Pseudomonas were significantly positively correlated with the contents of total nitrogen and total phosphorus. This study systematically analyzed the petroleum hydrocarbon, physico-chemcial properties and microbial communities in the soil of different oil exploitation sites, and revealed the specific dominant bacterial genera and microbial communities in the soil of Liaohe Oilfield. Our results provided a theoretical basis for functional bacterium screening and microbial community construction in the remediation process of petroleum contaminated soil in Liaohe Oilfield, and a reference for efficient degradation bacteria screening in other oilfields.

Enzyme cocktail containing NADH regeneration system for efficient bioremediation of oil sludge contamination.

Oil sludge is one kind of toxic and persistent contamination to ecology system from petroleum industry. In order to recycle contaminated sands and reduce environmental impacts at a lower operating cost, enzyme cocktail 21/CbFDH including NADH regeneration system for oily sludge bioremediation was constructed for the first time. The intracellular enzymes of oil-degrading strain Acinetobacter calcoaceticus 21 were prepared and the formate dehydrogenase gene Cbfdh from Candida boidinii was cloned and functionally expressed in E.coli BL21 induced by lactose. The activity and stability of CbFDH was enhanced through self-induction medium optimization using Box-Behnken design. The CbFDH activity was 12.2 times increased and was only decreased 3.9% upon storage at 30 °C for 5 d. The CbFDH increased the degradation rate of oil in high concentration. For the sludge with 10% oil (w/w), the degradation rate achieved 35.6% after 12 h using enzyme 21/CbFDH with the protein ratio of 1:4. The results will provide novel perspectives for creation and operation of petroleum-degrading enzymes involving formate dehydrogenase with higher efficiency and lower cost comparing to current microbial strains or consortium.

Novel Bacillus cereus strain from electrokinetically remediated saline soil towards the remediation of crude oil.

A new strain SWH-15 was successfully isolated after initial electrokinetic remediation experiment using the same saline soil sampled from Shengli Oilfield, China. Four methods (morphological and biochemical characteristics, whole-cell fatty acid methyl esters (FAMEs) analysis, 16S rRNA sequence analysis and DNA G + C content and DNA-DNA hybridization analysis) were used to identify the taxonomic status of SWH-15 and confirmed that SWH-15 was a novel species of the Bacillus (B.) cereus group. Then, we assessed the degrading ability of the novel strain SWH-15 to crude oil through a microcosm experiment with four treatments, including control (CK), bioremediation using SWH-15 (Bio), electrokinetic remediation (EK), and combined bioremediation and electrokinetic remediation (Bio + EK). The results showed that the Bio + EK combined remediation treatment was more effective than the CK, Bio, and EK treatments in degrading crude oil contaminants. Bioaugmentation, by addition of the strain SWH-15 had synergistic effect with EK in Bio + EK treatment. Bacterial community analysis showed that electrokinetic remediation alone significantly altered the bacterial community of the saline soil. The addition of the strain SWH-15 alone had a weak effect on the bacterial community. However, the strain SWH-15 boosted the growth of other bacterial species in the metabolic network and weakened the impact of electrical field on the whole bacterial community structure in the Bio + EK treatment.

Distribution of ion contents and microorganisms during the electro-bioremediation of petroleum-contaminated saline soil.

This study investigated the distribution of ion contents and microorganisms during the electro-bioremediation (EK-Bio) of petroleum-contaminated saline soil. The results showed that soil ions tend to accumulate around the electrodes, and the concentration was correlated with the distance from the electrodes. The average soil ion content was 7.92 g/kg around the electrodes (site A) and 0.55 g/kg at the furthest distance from the electrodes (site B) after 112 days of treatment, while the initial average content was 3.92 g/kg. Smooth linear (R2 = 0.98) loss of soil ions was observed at site C, which was closer to the electrodes than site B, and had a final average soil ion content of 1.96 g/kg. The dehydrogenase activity was much higher in EK-Bio test soil than in the Bio test soil after 28 days of treatment, and followed the order: site C > site B > site A. However, the soil dehydrogenase activity dropped continuously when the soil ion reached very high and low concentrations at sites A and B. The soil microbial community varied in sample sites that had different ion contents, and the soil microbial diversity followed the order: site C > site B > site A. The applied electric field clearly enhanced the biodegradation efficiency for soil petroleum contaminants. However, the biodegradation promotion effects were weakening in soils where the ion contents were extremely high and low (sites A and B). These results can provide useful information for EK-Bioremediation of organic-contaminated saline soil.

Effects of different remediation treatments on crude oil contaminated saline soil.

Remediation of the petroleum contaminated soil is essential to maintain the sustainable development of soil ecosystem. Bioremediation using microorganisms and plants is a promising method for the degradation of crude oil contaminants. The effects of different remediation treatments, including nitrogen addition, Suaeda salsa planting, and arbuscular mycorrhiza (AM) fungi inoculation individually or combined, on crude oil contaminated saline soil were assessed using a microcosm experiment. The results showed that different remediation treatments significantly affected the physicochemical properties, oil contaminant degradation and bacterial community structure of the oil contaminated saline soil. Nitrogen addition stimulated the degradation of total petroleum hydrocarbon significantly at the initial 30d of remediation. Coupling of different remediation techniques was more effective in degrading crude oil contaminants. Applications of nitrogen, AM fungi and their combination enhanced the phytoremediation efficiency of S. salsa significantly. The main bacterial community composition in the crude oil contaminated saline soil shifted with the remediation processes. γ-Proteobacteria, ß-Proteobacteria, and Actinobacteria were the pioneer oil-degraders at the initial stage, and Firmicutes were considered to be able to degrade the recalcitrant components at the later stage.

Synergistic effects of bioremediation and electrokinetics in the remediation of petroleum-contaminated soil.

The present study evaluated the coupling interactions between bioremediation (BIO) and electrokinetics (EK) in the remediation of total petroleum hydrocarbons (TPH) by using bio-electrokinetics (BIO-EK) with a rotatory 2-D electric field. The results demonstrated an obvious positive correlation between the degradation extents of TPH and electric intensity both in the EK and BIO-EK tests. The use of BIO-EK showed a significant improvement in degradation of TPH as compared to BIO or EK alone. The actual degradation curve in BIO-EK tests fitted well with the simulated curve obtained by combining the degradation curves in BIO- and EK-only tests during the first 60 d, indicating a superimposed effect of biological degradation and electrochemical stimulation. The synergistic effect was particularly expressed during the later phase of the experiment, concurrent with changes in the microbial community structure. The community composition changed mainly according to the duration of the electric field, leading to a reduction in diversity. No significant spatial shifts in microbial community composition and bacterial numbers were detected among different sampling positions. Soil pH was uniform during the experimental process, soil temperature showed no variations between the soil chambers with and without an electric field.

Effect of electric intensity on the microbial degradation of petroleum pollutants in soil.

Electro-bioremediation is an innovative method to remedy organic-polluted soil. However, the principle of electrokinetic technology enhancing the function of microbes, especially the relationship of electric intensity and biodegradation efficiency, is poorly investigated. Petroleum was employed as a target organic pollutant at a level of 50 g/kg (mass of petroleum/mass of dry soil). A direct current power supply was used for tests with a constant direct current electric voltage (1.0 V/cm). The petroleum concentrations were measured at 3275-3285 nm after extraction using hexane, the group composition of crude oil was analyzed by column chromatography. The water content of soil was kept 25% (m/m). The results indicated the degradation process was divided into two periods: from day 1 to day 40, from day 41 to day 100. The treatment of soil with an appropriate electric field led the bacteria to have a persistent effect in the whole period of 100 days. The highest biodegradation efficiency of 45.5% was obtained after treatment with electric current and bacteria. The electric-bioremediation had a positive effect on alkane degradation. The degradation rate of alkane was 1.6 times higher in the soil exposed to electric current than that treated with bacteria for 100 days. A proper direct current could stimulate the microbial activities and accelerate the biodegradation of petroleum. There was a positive correlation between the electric intensities and the petroleum bioremediation efficiencies with a coefficient of 0.9599.

[Two phases bioremediation of oil contaminated soil from Liaohe oil field].

A treatment engineering of prepared bed was set up for the bioremediation of oil contaminated soil with oil in this study, soils contaminated with different type of oils were treated using composting process in the prepared bed and the treatment period was divided into 2 phases with total time of 210 days. When the concentration of total petroleum hydrocarbons (TPH), which consist of thin oil, high condensation oil, special viscous oil, and viscous oil, were in the range of 25.8-77.2 g.kg-1 dry soil, petroleum removal rates can reach 38.37%-56.74% by 53 days operation. In the second phase, total petroleum removal rates reached 66.59%-80.96% by the 156 days operation in the next year. The results showed that most hydrocarbon pollutants that are easier to be degraded were removed in the first phase, the remedying efficiency obviously dropped in the second phase.

[Bio-remediation techniques of crude oil contaminated soils].

The bioremediation of soils contaminated by different types of petroleum were carried out with composting process in a prepared bed. By the measures of nutrient- and microbiological agent addition, and moisture- and pH control, an ideal environment for microbes were obtained. When total petroleum hydrocarbons, which consist of thin oil, high condensation oil, special viscous oil, and viscous oil, were in the range of 25.8-77.2 g.kg-1 dry soil, the petroleum removal rate could reach 38.37-56.74% by 2 months operation. The contents of aromatic hydrocarbon, asphaltum and resin were important factors controlling the degradation of petroleum. 6 fungi, 6 bacteria and 1 actinomyces were found to be the dominant strains for petroleum degradation. The results could provide theoretical bases for remediation of soil contaminated by petroleum.