Crude Oil In Soil Research Articles

Enhancement of repeated inoculation strategy with a domesticated bacterial consortium on the biodegradation of high-level crude oil in soil

Repeated inoculation of hydrocarbon degrading microbes should be powerful to improve the survival of inoculant, which is vital to achieve efficient remediation of petroleum contaminated soil. This paper aims to study the repeated inoculation (with different inoculum size and time interval) enhanced bioremediation of high-level petroleum contaminated soil with a domesticated bacterial consortium. The copy number of bacterium and alkB gene, soil enzyme activities and microbial community structure during the remediation were systematically analyzed to preliminarily reveal the mechanism of repeated inoculation affecting remediation for the first time. The results revealed that repeated inoculation remarkably improved the total petroleum hydrocarbon (TPH) removal in soil (86.5 % in HC120) compared with a single inoculation (68.9 % in HA120). The TPH removal of repeated inoculation with high inoculum size (HC) on the 60th day was close to that of once inoculation (HA) on the 120th day, suggesting that repeated inoculation led to faster degradation. Interestingly, the effect of inoculation with low dose and more times (LC120, 78.5 %) was equal to that with high dose and less times (HB120, 78.0 %), even much better than that with high dose and once inoculation (HA120). Treatment HC had a significant impact on the soil bacterial diversity and community structure, and the dominant species in the inoculants, such as Stenotrophomonas and Pseudomonas, which was low abundance in the blank group (CK), still maintained high abundance during the remediation process. The soil catalase activities and the number of alkB gene were the highest in HC. Correlation analysis implied that repeated inoculation of hydrocarbon degrading bacteria did improve the survival of inoculant, soil enzyme activities and maintain the number of degrading bacteria, thus promoting the TPH removal. These findings will facilitate the practical application of bioremediation technology to contaminated environment, which has important environmental and economic benefits.

Biochar-mediated bioremediation: a sustainable strategy to increase Avena sativa L. tolerance to crude oil soil contamination

The present work investigated the effects of different doses of biochar (2.5%, 5%, 10%), a by-product of the pyrolysis of woody biomass, on the growth of oat plants (Avena sativa L., cv “Danko”) grown under different crude oil concentrations (0.5%, 1%, 2%, 3%, 6%) added to the soil, evaluating both biometric (i.e. fresh weight) and biochemical (i.e., content of malondialdehyde and proline, and total antioxidant power) parameters. The findings indicate that biochar positively influences the fresh weight of oat plants across all concentrations of crude oil investigated. On the other hand, regarding oxidative stress, measured by malondialdehyde and proline content, biochar led to a significant reduction, with statistical significance observed at biochar concentrations > 2.5% and crude oil levels > 2% (malondialdehyde: ranging from -25% to -38%; proline ranging from -33% to -52%). Soil amendment with biochar increased the total antioxidant power, particularly at biochar concentrations > 2.5% and crude oil levels > 2% (ranging from + 20% to + 98%). These results suggest that biochar has a great potential in mitigating the negative effects of crude oil contamination on plant growth and oxidative stress levels, thereby highlighting its value as a conditioner in contaminated soils.

Hydrophobic modified melamine sponge for highly effective remediation of crude oil in water and soil

Crude oil pollution in water and soil has resulted in considerable environmental damage. The utilization of hydrophobic and oleophilic sponge materials for the treatment of crude oil pollution has garnered significant interest, owing to their excellent selective adsorption performance. In this paper, superhydrophobic and superoleophilic sponges (SMF) are prepared by a simple silane hydrolysis-thermal curing method, which is low-cost, environmentally friendly, large-scale preparation, acid and alkali-resistant, and mechanically stable. They can be used for the remediation of oil pollutants in water and soil simultaneously, and show high efficiency, excellent stability, and biosafety. Under appropriate circumstances, SMF is capable of adsorbing up to 82.7 g/g of crude oil in water and eliminating over 70.0 % of crude oil in soil, while exhibiting exceptional recycling performance. Notably, this study introduces a novel technique that alters soil viscosity by controlling soil water content, in conjunction with SMF, for the removal of crude oil in soil. Consequently, SMF shows great promise for practical application in the remediation of oil pollutants in both water and soil.

Vertical migration and variation of crude oil in soil around typical oilfields under natural leaching

Vertical migration and variation of crude oil in soil around typical oilfields under natural leaching

Enhanced crude oil degradation and reshaped microbial community structure using straw-sludge biochar-persulfate oxidative system in oil-contaminated soil

The straw-sludge biochar is an environmentally friendly and novel alternative activator. In this study, a novel biochar (SSBC), co-pyrolyzed by waste rice straw and municipal sludge using ZnCl2 activation method, was applied in persulfate (PS)-based remediation for crude oil in soil, which has a high efficiency up to 69.11% in 35 days. Compared with sludge-BC, SSBC had a higher surface area of 667.81 m2‧g−1, pore volume of 0.47 cm3‧g−1, and pore surface area of 233.22 m2‧g−1, FT-IR showed that SSBC is in richer surface functional groups, e.g., -COOH with a content of 1.03 mM‧g−1 and -OH with a content of 2.77 mM‧g−1, which were responsible for its good PS activation performance. Besides, the EPR results showed that SSBC activated PS to generate SO4−• and •OH, which certainly supported the construction of the system. In SSBC-PS oxidative system, the SSBC dosage (0.03 g), the PS dosage (1 mM) and the initial pH value (7) of the system were optimized, and it were applied in oil-contaminated soil. Owing to the SSBC-PS oxidative system, the crude oil degradation rate reached to 34.17% in first week. And these long-chain alkanes were oxidized to short-chains, or cyclane and aromatics were oxidized into short-chain alkanes. Besides, the relative abundance of potential crude oil degraders greatly increased finally, including Alcanivorax (12.52% ∼ 12.86%), Marinobacter (10.78% ∼ 12.54%), Aliifodinibius (7.01% ∼ 7.09%) and Salinisphaera (6.55% ∼ 7.16%), which changed organic pollutions to CO2 and H2O via TCA cycle in crude oil degradation process. Consequently, the combination of SSBC-PS oxidative system and indigenous microbes would be a potential application in crude oil-contaminated soil remediation.

Enhanced crude oil degradation by remodeling of crude oil-contaminated soil microbial community structure using sodium alginate/graphene oxide/Bacillus C5 immobilized pellets

Bioaugmentation (BA) of oil-contaminated soil by immobilized microorganisms is considered to be a promising technology. However, available high-efficiency microbial agents remain very limited. Therefore, we prepared a SA/GO/C5 immobilized gel pellets by embedding the highly efficient crude oil degrading bacteria Bacillus C5 in the SA/GO composite material. The optimum preparation conditions of SA/GO/C5 immobilized gel pellets were: SA 3.0%, GO 25.0 μg/mL, embedding amount of C5 6%, water bath temperature of 50°C, CaCl2 solution concentration 3% and cross-linking time 20 h. BA experiments were carried out on crude oil contaminated soil to explore the removal effect of SA/GO/C5 immobilized pellets. The results showed that the SA/GO/C5 pellets exhibited excellent mechanical strength and specific surface area, which facilitated the attachment and growth of the Bacillus C5. Compared with free bacteria C5, the addition of SA/GO/C5 significantly promoted the removal of crude oil in soil, reaching 64.92% after 30 d, which was 2.1 times the removal rate of C5. The addition of SA/GO/C5 promoted the abundance of soil exogenous Bacillus C5 and indigenous crude oil degrading bacteria Alcanivorax and Marinobacter. In addition, the enrichment of hydrocarbon degradation-related functional abundance was predicted by PICRUSt2 in the SA/GO/C5 treatment group. This study demonstrated that SA/GO/C5 is an effective method for remediating crude oil-contaminated soil, providing a basis and option for immobilized microorganisms bioaugmentation to remediate organic contaminated soil.

Phytoremediation of Crude Oil Polluted Soil Using Dried Yam Peels (Discorea sp) as a Case Study in Niger Delta Environment of Southern Nigeria

This study aimed at enhancing the remediation of crude oil polluted soil using yam peels. 2kg of the soil samples were polluted crude oil at different concentrations ranging from 5%, 10% and 15%. There were three amended and un-amended samples each labeled A-F. The amended samples were A, C and E which contained the following respectively, 5% polluted soil + 150g yam peels, 10% polluted soil + 150g of yam peels and 15% polluted soil + 150g yam peels. The un-amended samples were B, D and F which were called the control samples with 5%, 10% and 15% concentration of crude pollutant. Parameters such as soil moisture content, total organic carbon, pH and total hydrocarbon content were analyzed before and after remediation. The result showed that yam peels enhanced remediation of the soil especially in treatment A. The reduction in Total Hydrocarbon Content was highest in the 5% crude oil polluted soil sample resulting 57.4% and least at 15% polluted control sample resulting 44.2%. The higher the concentration of crude oil in the soil the lower the percentage degraded. Yam peels which are agro waste can enhance biodegradation of crude oil in polluted soil and therefore can act as remediating agent.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of –NH2 on chitosan and –COOH on biochar, forming a new chemical bond –NH–CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%–33.09%), Bacillus (3.01%–4.10%), Dietzia (1.84%–5.56%), Pseudomonas (0–0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.

Bioremediation of crude oil and its effect of residue in growth of wheat plants

Three strains of bacteria were studied to bioremediation crude oil in soil and in the laboratory. These bacteria were Azospirillum spp., Azotobacter spp. And Rhizobium spp. The results showed that Azospirillum spp. , Rhizobium spp. was more efficiency to bioremediation crude oil than Azotobacter spp., also the results showed that the higher number of bacteria was recorded in soil treatment with Rhizobium spp. in presence of crude oil in first week , and the number of this bacteria reached to 22.6 x 108 , but the lowest number of bacteria was recorded in soil without added crude oil (control), and the number reached to 2 x 107.The statistical methods obtained that no significant were recorded between different treatments . Also, the results showed that the numbers of bacteria in soil treatment with crude oil were decreased regularly from second week until ten weeks. The results showed that the height of the aerial parts of wheat plants reached to 73 cm in soil treatment with Azotobacter spp. And crude oil after 10 weeks, and the lower length reached to 47 cm. At the same time the results obtained that the higher wet weight of wheat plants was reached to 56 gm in soil treatment with Rhizobium spp., and in the presence of crude oil after 10 weeks, but the lower wet weight was reached to 25 gm in control. Also, the results showed that the higher of dry weight of wheat plants was reached to 23 gm in soil treatment with Rhizobium spp. and in the presence of crude oil after 10 weeks, but the lower dry weight was reached to 10 gm in control, however the statistical methods that no significant were recorded between the different treatments. Also, that all these bacteria have ability to removal crude oil in soil and in mineral salts medium.

Biodegradation potential of native hydrocarbon degrading bacteria by using bio-stimulation on crude oil in soils of Khuzestan province (Abadan, Ahvaz and Andimeshk) –Iran

Soil bioremediation using microorganisms is a safe, inexpensive and environmentally friendly method designed to remove hazardous pollutants. In this study, a consortium of native bacteria isolated from three different soil types in Khuzestan Province was used. Result show that the data follow the quadratic equation and consortium isolated from the soil of Abadan was selected as a desired consortium for confirmatory tests. By increasing humidity content, the percentage of TPH removal also increased. (NH4)NO3 was selected as the best nitrogen source by the software and by increasing the concentration of nitrogen, the percentage of TPH removal also increased. The best yield for total petroleum hydrocarbons removal was observed when saline soil was used as a soil sample, the reasons for which can be related to the better yield of the consortium separated from Abadan soil. By increasing the amount of hydrocarbons, the percentage of TPH removal reduced, and the two are inversely related, and the lower the initial amount of hydrocarbon, the more desired the conditions for faster adaptation of microorganisms and less toxicity of the environment, and percentage of TPH removal increased.

REMEDIATION OF CONTAMINATED SOIL WITH CRUDE OIL BY COMPOSTING

In recent years, one of the primary issues noted worldwide in the environment is the contamination of crude oil in soil. In comparison to traditional methods, bioremediation offers a potential alternative for removing hydrocarbon pollution from the environment. This review paper gives an overview of the benefits, mechanism, and operation of aerobic composting remediation of soil contaminated with crude oil. Within this study, it was demonstrated that with composting technology, one could successfully treat crude oil contaminated soil with a > 90% removal efficiency. Aerobic composting utilizes aerobic bacteria and fungi that require oxygen to grow and biodegrade crude oil’s biological component into carbon dioxide and water, whereas anaerobic composting utilizes anaerobic microbes that grow in the absence of oxygen and convert the crude oil’s organic component primarily into methane. In terms of efficiency, biodegradation capacity, and rate, aerobic conditions outperform anaerobic conditions. Numerous parameters have been discussed and demonstrated to have an effect on the composting condition and also on the bacteria and fungi used to biodegrade crude oil contaminants at various stages of the composting process, including initial concentration, soil type, soil/compost ratio, aeration rate, moisture content, C/N ratio, pH, and temperature. Microbes use crude oil organic matter as carbon and energy sources during the composting process, whereas fungi produce enzymes that catalyze crude oil oxidation reactions. It is believed that the mutualistic and competitive interactions between bacteria and fungi maintain a robust biodegradation system. The thermophilic phase exhibited the highest rate of biodegradation. However, the presence of a diverse and dynamic microbial community throughout the composting process ensures that crude oil degradation occurs. The efficient composting processes using specific microbes need to be investigated.

Evaporation of Heavy Crude Oil in Soil

Heavy crude oil spillage on soil threatens productivity and affects the natural biota of the ecosystem. Evaporation is an important parameter increases crude oil density, viscosity and fraction of lower molecular weight substances which reduce its infiltration into the soil and groundwater. The evaporation of heavy crude oil showed API of 21.5, viscosity of 15mm2/s, density 0.8952 g/cm3, pour point of 11.37. The crude oil was exposed to solar radiation for 35 days. The percentage reduction in mass of the crude oil and temperature on five day interval showed 8.22(38OC) on day 0, on day 5 was 8.13(34oC), on day 10 was 5.92(39oC), on day 15 was 5.38(39oC), on day 20 was 3.16(37oC), on day 25 was 2.94(31oC), on day 20 was 2.56 (41oC) and on day 35 was 1.79(38oC). The lighter molecules evaporated first leaving the heavier molecules behind causing a reduction in the rate of evaporation with time. This analysis will be provide insight to modelling oil spill in terrestrial ecosystem.

Determination of total petroleum hydrocarbons (TPHs) in weathered oil contaminated soil

A new measurement method of weathered crude oil in soil was reviewed. There is no standard method for the extraction of crude oil from soil. Hence, a basic initial test was carried out and several methods such as gravimetric and gas chromatography-mass spectrometry (GC-MS) with various parameters such as weight, solvent and time. The gravimetric process was demonstrated to be the most effective for quantifying weathered contamination crude oil in contaminated soil. The dichloromethane DCM, mixture of DCM: hexane (1:1 v/v mix) and the mixture of acetone: hexane (1:1 v/v mix) were used to investigate the ability of solvent extraction technique for removing weathered crude oil from soil under various extraction conditions. The mixture of acetone: hexane (1:1 v/v mix) was demonstrated to be the most effective in removing total petroleum hydrocarbons (TPH) from contaminated soils. 5 g and 1 g weights of oil-contaminated samples were studied to select the best weight depending on contamination level. 1 g of contaminated soil was cleaned in three cycles whilst the 5 g of contaminated soil required six cycles. The selected parameters recovered about 97.20% of the weathered crude oil. These parameters were influenced with character of high efficiency, low cost, low toxicity, and short time.

Re-biodegradation of all alkanes after chemical oxidation in soils

This study aimed to investigate the rapid restoration of indigenous hydrocarbon degraders after chemical oxidation, in order to enhance the subsequent biodegradation of crude oil in soils. The Fe-SOM (2231 mg kg−1) and H2O2 were added into the oil-contaminated soil (total petroleum hydrocarbon (TPH): 16064 mg kg−1) for chemical oxidation. Then, the all and partial alkane re-biodegradation reagents were added for re-biodegradation experiments. Calculated and analyzed C-source (DOC and TPH) and N-source ( $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ , $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ , $$ {\mathrm{NO}}_2^{-}-\mathrm{N} $$ ) consumption and the population of hydrocarbon degraders in each period. After chemical oxidation, the total biodegradation of all alkanes (re-biodegradation degree: 100%) with reagent for all alkane re-biodegradation in the late stage was higher than that in the early stage. Further study found that DOC was the main C-source and $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ was the main N-source in the early stage, while TPH and nitrate were the main C&N-sources in the late stage of re-biodegradation. In other words, the C&N-sources changed over to TPH and nitrate in the late stage. After re-biodegradation stage, increasing biodegradation (from 644 mg kg−1 in the 1st stage to 842 mg kg−1 in the 3rd stage) was observed. The results showed that re-biodegradation of all alkanes could recover growth of indigenous hydrocarbon degraders and continuously increase biodegradation of all alkanes after chemical oxidation. The C&N-sources changed from DOC and $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ to all alkanes and $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ during re-biodegradation stage was the key factor.

Biodegradation of buried crude oil in soil microcosm by fungal co-culture

Crude oil pollution in soil is a major environmental problem over the world. After long-term contamination, crude oil can be buried in the soil and leaving the toxic and persistence compounds. Treatment of buried crude oil in soil is a major challenge. In this study, buried crude oil in soil (20 cm-depth) was treated by the co-culture of three fungal strains (Pestalotiopsis sp. NG007/Polyporus sp. S133/Trametes hirsuta D7 with composition 1/1/1 and pre-grown in wood meal) placed on the top or bottom layer of the soil. Biodegradation behavior of crude oils were analyzed at different depth interval (0–5 cm, 5–15 cm, and 15–20 cm) with constant oxygen diffusion. The results showed that both position of fungal co-culture could degrade crude oil 63 – 92% after 30 days. Placing the co-culture in the bottom layer position of the soil demonstrated more effective degradation for all the depth interval than that of the top layer position. During the biodegradation, the co-culture produced oxidative enzymes such as catechol 1,2-dioxygenase, catechol 2,3-dioxygenase, laccase, manganese peroxidase, and lignin peroxidase with significant activities. This study offers an important strategy to remediate crude oil contaminated soil, specifically buried crude oil.

The Effect of Fertilizer on Epipremnum Aureum in Phytoremediating Soil Contaminated with Crude Oil

Epipremnum aureum is a common ornamental foliage which is used mainly for indoor decoration. It demonstrates tolerance to low light environment and the ability to remove atmospheric chemicals such as gasoline and formaldehyde. A previous screening study showed the ability of Epipremnum aureum to remove crude oil from soil. Further to the screening study, this study examined the effect of fertilization on phytoremediation of crude oil-contaminated soil by Epipremnum aureum Epipremnum aureum was grown in pots with soil contaminated with 5%, 10% and 15% of crude oil by weight respectively, with and without the addition of fertilizer. In line with previous study, Epipremnum aureum showed the ability to remove crude oil contaminants. The plant demonstrated highest crude oil removal rate in pots with 15% contamination. Application of fertilizer enhanced the removal of crude oil in all experimental pots by Week 6, hence increasing the rate of crude oil decline over the experimental duration. It is deemed that application of fertilizer provides nutrients to promote plant growth and proliferation of roots which enhance rhizodegradation of crude oil in soil. This study extends on the existing knowledge that Epipremnum aureum can phytoremediate crude-oil contaminated soil by characterizing its tolerance to crude oil and its response to fertilization, which is crucial to its practical application in phytoremediation. Phytoremediation presents a promising yet cost-effective measure in treating contaminated land. Further study can examine the optimum fertilizer concentration for phytoremediation and the tolerance level of Epipremnum aureum to crude oil contamination.

Enhanced biodegradation of crude oil in soil by a developed bacterial consortium and indigenous plant growth promoting bacteria

This study aimed to develop an efficient, cost-effective and eco-friendly bacterial consortium to degrade petroleum sludge. Four bacterial strains belonging to genera Acinetobacter and Pseudomonas were selected to constitute three different consortia based on their initial concentration. The highest degradation rate (78%) of 1% (v/v) crude oil after 4weeks of incubation was recorded when the concentration of biosurfactant (BS) producing isolate was high. Genes, such as alkB, almA, cyp153, pah-rhdGN, nah, phnAC and cat23 were detected using the polymerase chain reaction method and their induction levels were optimal at pH 7·0. A crude oil sludge was artificially constituted, and its bacterial composition was investigated using 16S rRNA gene amplicon sequencing. The results showed that the soil bacterial community was dominated by plant growth-promoting bacteria (PGPB) after crude oil treatment. Our findings indicate the decontamination of the crude oil contaminated soil was more effective in the presence of both the constituted consortium and PGPB compared to the presence of PGPB alone. This study showed that the PGPB (Taibaiella) present in petroleum uncontaminated soil can promote the soil decontamination. The addition of both efficient hydrocarbon-degrading and BS producing bacteria is also necessary to improve the decontamination.

Fate of Crude Oil in Soil Treated with Pseudomonas putida Immobilized on Coconut Coirpith a Lowcost Biocarrier

ABSTRACT An attempt was made to study the use of bacterial species Pseudomonas putida immobilized on coconut coir pith to degrade Total Petroleum Hydrocarbon (TPH) present in soil contaminated with crude oil. The soil was spiked with crude oil to get a concentration of 10,000 mg/kg soil. The bacterial species Pseudomonas putida was immobilized on coconut coir pith and used for the degradation of crude oil. The experiment was conducted with four treatments such as T1 (Control (Soil alone)), T2 (Soil + Nutrients + Pseudomonas putida), T3 (Soil + Nutrients + Coconut coir pith), T4 (Soil + Nutrients + Pseudomonas putida immobilized in Coconut coir pith) for 60 days. During the period of the experiment the parameters viz., soil pH, temperature, moisture content, and percent degradation of the TPH compounds were determined. The results revealed that the percent degradation of the TPH was found to be highest for the treatment T4 and at 60th day maximum degradation was recorded. The percent degradation of some of the TPH compounds such as dotriacontane, octane, octacosane, octatriacontane was 45.0, 45.5, 45.2, and 44.5, respectively. The coconut coir pith immobilized with bacterial species Pseudomonas putida can, therefore, prove to be a very good biological treatment option to remediate crude oil-contaminated soils.

Fast-stimulating bioremediation of macro crude oil in soils using matching Fenton pre-oxidation

This study aims at exploring the mechanism of fast-stimulating bioremediation of macro crude oil using matching Fenton pre-oxidation. The 80-day biodegradation experiment for soil S1 and S2, containing macro crude oil: C19–C29 and C17–C29 respectively, was conducted after Fenton pre-oxidation with three concentrations of H2O2 (225 mM, 450 mM, and 900 mM). Experimental results indicated that the bioremediation efficiency of macro crude oil was up to 57.1% (8853 mg/kg, S1) and 64.4% (11,719 mg/kg, S2) for 80-day fast-stimulating bioremediation using matching Fenton pre-oxidation (450 mM H2O2), which was 1.8–2.6 times that (S1: 22.2–37.1%; S2: 36.1–39.6%) for slow-stimulating bioremediation using un-matching Fenton pre-oxidation. Furthermore, the high-throughput analysis revealed that genera Sedimentibacter, Caenispirillum, and Brevundimonas became the dominant bacteria after matching Fenton pre-oxidation. Meanwhile, the highest logarithmic growth rate of indigenous hydrocarbon degraders (IHD) was obtained (S1: 64% and S2: 60%) for fast-stimulating bioremediation. And the consumption of NH4+-N was up to 90% and 94% in S1 and S2 within 60 days for fast-stimulating bioremediation, approximately 1.4 and 2.2 times that (S1: 65% and 62%; S2: 47% and 41%) for slow-stimulating remediation. The results showed that the macro crude oil became the main carbon source for IHD for the fast-stimulating bioremediation, resulting in the rapid growth of IHD. Thus, this study provides a fast and efficient remediation technology for bioremediation of macro crude oil-contaminated soils.

The effect of organic chelates and gibberellic acid on petroleum hydrocarbons degradation in the soil co-contaminated with Ni and crude oil under canola cultivation

Background: Soil remediation is one the important problem in environmental studies. Thus, this research was conducted to evaluate the effect of organic chelates and gibberellic acid (GA3 ) on the degradation of crude oil in the soil co-contaminated with Ni and crude oil under canola cultivation. Methods: For treatments, HEDTA and NTA chelates at rates of 0 and 2.5 mmol/kg soil and foliar GA3 (0 (GA3 (-) and 0.05 (GA3 (+) mM) were used. In addition, the soil was polluted with Ni (0 and 100 mg Ni/kg soil) and crude oil at rates of 0, 2, and 4% (W/W). The plant used in this experiment was canola. The concentration of Ni in soil and plant was measured using atomic absorption spectroscopy (AAS). The concentration of total petroleum hydrocarbon (TPH) was measured using GC-mass. The mean differences were calculated according to the least significant difference (LSD) test. Results: The greatest degradation of crude oil belonged to the non-Ni-polluted soil under cultivation of GA3 -treated plant, while the lowest one was observed in the soil received the greatest level of HEDTA and NTA chelates. Applying 0.05 mM GA3 foliar significantly increased the degradation of crude oil in soil and Ni in plant shoot by 12.1 and 8.3%, respectively. In addition, soil microbial respiration was also increased by 11.3%. Conclusion: HEDTA, NTA, and GA3 had a significant effect on the Ni phytoremediation efficiency and degradation of crude oil in soil that is a positive point in environmental pollution. However, the role of soil physico-chemical properties on the phytoremediation efficiency cannot be ignored.