Soil Total Petroleum Hydrocarbon Research Articles

Total Petroleum Hydrocarbons in Soil of Different Oil Fields at Basrah Governorate, Iraq

Objectives: This study concentrated on determining the total hydrocarbon concentrations in soil at eleven stations of the oil field (Seba, Safwan, Majnoon, Ratawi, Bergezia, Qurna2, Qurna1, Shuaaba, South and North Rumaila, and Al Zubair). Methods: Soil samples were freeze-dried, finely pulverised in an agate mortar, and sieved through a 62-um metal sieve and 150 ml mixture of methanol and benzene (1:1) was used to extract the soil. Determination of TPHs where determined by using Spectrofluroscence, Total organic carbons (TOC) in the soil of the oil fields were also determined. Results: According to the TPH distribution used in this investigation, station 11 (Al Zubair) had the highest concentration of TPHs (162.53mg/g dry weight), while station 1(Seba) had the lowest concentration (21.4mg/g dry weigh). Additionally, the study's findings demonstrated that TPH levels varied spatially amongst sites. The highest amounts of total petroleum hydrocarbons detected in soil samples, as well as the findings of this investigation indicating that TPH levels varied geographically throughout stations. Conclusions: There is significant correlation between the TPH in soil and TOC%. By comprising the result concentration of this study with literature reviews, the concentration levels lies within it and in other cases exceed it.

Metagenomic analysis of a thermophilic bacterial consortium and its use in the bioremediation of a petroleum-contaminated soil

Biodegradation is difficult at high temperatures due to the limited capacity of microorganisms to survive and function outside their optimum temperature range. Here, a thermophilic petroleum-degrading consortium was enriched from compost at a temperature of 55 °C. 16S rDNA and metagenomic techniques were used to analyze the composition of the consortium and the mechanisms of degradation. The consortium degraded 17000 mg total petroleum hydrocarbons (TPHs) L-1 with a degradation efficiency of 81.5% in 14 days. The consortium utilized a range of substrates such as n-hexadecane, n-docosane, naphthalene and pyrene and grew well over a wide range of pH (4-10) and salinity (0-90 g L-1). The hydrocarbon-degrading extremophilic consortium contained, inter alia, (relative abundance > 1%) Caldibacillus, Geobacillus, Mycolicibacterium, Bacillus, Chelatococcus, and Aeribacillus spp. Metagenomic analysis was conducted to discover the degradation and environmental tolerance functional genes of the consortium. Two alkane hydroxylase genes, alkB and ladA, were found. A microcosm study shows that the consortium promoted the bioremediation of soil TPHs. The results indicate that the consortium may be a good candidate for the high-temperature bioremediation of petroleum-contaminated soils.

Velocity Influence on Transport Model of Total Petroleum Hydrocarbon in Soil and Ground Water

Velocity Influence on Transport Model of Total Petroleum Hydrocarbon in Soil and Ground Water

Bioavailability enhancement of petroleum-contaminated soil by electrokinetic remediation

The Electro kinetic Remediation Technology (EKR) is recognized as the most potential remediation technology for soils with low permeability, like clay soil characteristics. Electrokinetic treatment could increase the bioavailability of contaminants in bioremediation petroleum-contaminated soil. The study, “Bioavailability enhancement of petroleum contaminated soil by electrokinetic remediation,” is experimental research in a laboratory to improve the bioavailability of petroleum hydrocarbons on clay during bioremediation with initial treatment using electrokinetic remediation techniques, finding optimum electrokinetic operating conditions of remediations, and analyzing the mechanism of remediation process in contaminated soil. Bioavailability enhancement was studied for 35 days. Polluted soil was treated with an electrokinetic box test (17cm×12cm×10cm), and DC power was used for 48 hours. Total Petroleum Hydrocarbon (TPH) concentration was determined by gravimetric methods. The results showed that the characteristics of the soil samples were dominated by 49.31% clay. The initial concentration of TPH in polluted soil is 3.7%. The electrokinetic applications during 48 hours and followed by bioremediation for 35 days those processes removed TPH up to 80.74 % (from 33780.66 mg HC (kg dry w)-1 to 6506.155176 mg HC (kg dry w)-1. There is an increase in bioavailability indicated by the rise in bacterial populations and an increase in biodegradation after electrokinetic remediation. With this approach, bioavailability has been increased by 70.18%. Bio-electrokinetic remediation is the recommended method for polluted clay soils with low bioavailability.

Soil residue ecotoxicology from biosurfactant extraction for oily soil decontamination process

Solvent extraction as part of oily soil decontamination process has been including rhamnolipid biosurfactant to be part for seeking its possibility for further implementation. Result of some researchers reported prospect of its implementation due to removal efficiency. This study reported post treatment process assessment to soil residue that remained after the completion of decontamination process. Soil toxicity examined involving Total Petroleum Hydrocarbon (TPH) concentration, Hydrocarbon Structure by using Gas Chromatography-Flame-Ionization Detection (GC-FID), Hydrocarbon bond identification by using Fourier Transform Infra-Red Spectroscopy (FTIR), Toxicity Characteristics Leaching Procedure (TCLP) analysis, Metal and Oxide Metal Content of the residual soil. Germination Index as biological indicator also involved as part of the study to give early indication of impact on residual treated soil. Germination index selected mung bean (Phaseolus radiatus) as object of study. Result showed that at residual soil TPH content could be reduced until 0.78%, there are simplification of hydrocarbon structure after treatment process included weakened of hydrocarbon bonding and concentration observed by FTIR. TCLP result showed residual soil was benign to the environment and Germination Index indicated improvement of mung beans germination after decontamination process.

Remediation of diesel-oil contaminated soils using an innovative nanobubble and electrolyzed catalytic system

Soil contamination resulting from petroleum hydrocarbons poses a significant environmental challenge. In this research, an innovative electrolyzed catalytic system was devised to produce nanobubble-enriched catalytic water, which was employed for remediating soils contaminated with diesel oil. This novel system harnessed high voltage (220 V) via direct current, utilizing titanium electrodes coated with iridium dioxide. The inclusion of iron-copper hybrid oxide catalysts between the electrodes was instrumental in enhancing the efficiency of radical generation. The study employed the electron paramagnetic resonance (EPR) technique and the Rhodamine B (RhB) method to analyze the species and concentration of the generated radicals. EPR is a versatile tool for investigating materials with unpaired electrons and is capable of quantifying reaction kinetics for transition metals. RhB can be used as a probe for hydroxyl radical concentration determination. The addition of an electrolyte (NaCl or K2SO4) could enhance the electrolytic reaction and improve radical production rate. By incorporating 20 mM of K2SO4 and utilizing 75 g of catalyst per 500 mL batch of nanobubble-contained electrolyzed catalytic water (NECW) production, with a current density of 20 mA/cm2, a highly oxidized nanobubble-infused electrolyzed catalytic water was successfully generated. This water exhibited an oxidation-reduction potential of 887 mV and contained a radical concentration of 7.6 × 10−13 M, encompassing hydroxyl, superoxide, and sulfate radicals. Furthermore, it displayed a negative zeta potential of −39.8 mV, along with nanobubbles averaging 28 nm in diameter and a nanobubble density of 3.7 × 109 particles per milliliter. The presence of nanobubbles in electrolyzed catalytic water, owing to their negative zeta potential and nano-scale attributes, imparts a repulsive force that hinders bubble aggregation and prolongs their existence. When these nanobubbles burst, the resulting radicals contribute to an augmented radical concentration, which, in turn, facilitates the oxidation of petroleum hydrocarbons. Approximately 72.4% of the total petroleum hydrocarbon in soils could be removed (dropped from 3230 mg/kg to 892 mg/kg) after five batches of NECW washing (10 min of each washing time) via the desorption and extended chemical oxidation mechanisms. The total petroleum hydrocarbons in the water phase could be removed entirely after pumping the polluted water into the electrolyzed catalytic system for immediate treatment, indicating that the electrolyzed catalytic system could oxidize the desorbed total petroleum hydrocarbon effectively. The findings demonstrate that the nanobubble-infused catalytic water generated by the innovative electrolyzed system effectively and efficiently remediates petroleum-hydrocarbon-contaminated soils and water, all while minimizing the risk of secondary pollution.

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.

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.

Omics shed light on the mechanisms of petroleum‐contaminated soil remediation: When biochar meets nitrogen

AbstractDecontamination of oil‐affected soil is an urgent worldwide issue. In this study, a microcosm experiment was conducted to explore the effect of combined utilization of urea and biochar on oil‐contamination remediation in an eastern China oil‐field soil and explored their impact on soil physicochemical properties, organic pollutants degrading‐related enzyme and functional genes, microbiome, and metabolome. Then, a pot experiment was conducted to verify the impact of the remediation experiment. Results showed that a combined application of biochar and nitrogen reduced 78.6% of total petroleum hydrocarbons in soil. Combined treatment enhanced soil dehydrogenase and catalase activities, alkB, and CYP gene abundances relative to Control. Moreover, nitrogen input reduced soil microbial α‐diversity, while improving the relative abundances of Alcanivorax and Pseudogym. In addition, the pathways of glyoxylate and dicarboxylate metabolism, naphthalene and anthracene degradation, butanoate metabolism, pyruvate metabolism, and glycolysis or gluconeogenesis were up‐regulated in combined treatment relative to Control. Besides, both biochar and nitrogen addition can increase the number of edges and clustering coefficient of the microbial network, and improve the network robustness. The pot experiment showed that combined treatments enhanced ryegrass shoot length, root length, and biomass by 57.8%, 38.5%, and 42.8%, respectively. Overall, this study proved the feasibility of combined biochar and urea co‐application in remedying oil‐contaminated soil and shed light on the inner mechanism.

Diversity and Biotic Index of Wild Pioneer Plants as Potential Bioindicators of Crude Oil-Contaminated Soil in Siak Regency, Riau Province, Indonesia

This study aims to determine the spatial variations in the diversity of wild pioneer plants along the gradation of crude oil-polluted soils and to analyze their biotic potential as a bioindicator of crude oil-contaminated soils in Siak Regency. Sampling was done in three oil wells using a purposive sampling method (center, edge, far from the well) measuring 1 x 1 m2. The soil at each contamination gradation was composited and analyzed for Total Petroleum Hydrocarbon (TPH) content. Vegetation data were analyzed using biotic indices such as density, Shannon-Wiener distribution index, species richness, rate of endemism, and importance value index. Potential bioindicator was analyzed by regression analysis, biplot, and IndVal. The results showed spatial variations in colonization, diversity, and structure of pioneer plants along the gradation of oil contamination. Species from the Cyperaceae, notably Scleria sumatrensis, Cyperus rotundus, and Fimbristylis ovata, were found in the center of the contamination area and resistant to oil contamination. The regression and biplot analysis revealed that along with the increasing soil TPH, the species richness and diversity index tended to decline, but the rate of endemism increased. IndVal analysis showed that C. rotundus and S. sumatrensis showed a potential bioindicators of oil-contaminated soils with TPH content of 2,700 to 3,300 ppm, while F. ovata, Panicum repens, and Imperata cylindrica was potential for TPH 692 to 851 ppm. Mimosa pudica was a sensitive plant and found on the soil TPH 73 ppm.

Diversity and Biotic Index of Wild Pioneer Plants as Potential Bioindicators of Crude Oil-Contaminated Soil in Siak Regency, Riau Province, Indonesia

This study aims to determine the spatial variations in the diversity of wild pioneer plants along the gradation of crude oil-polluted soils and to analyze their biotic potential as a bioindicator of crude oil-contaminated soils in Siak Regency. Sampling was done in three oil wells using a purposive sampling method (center, edge, far from the well) measuring 1 x 1 m2. The soil at each contamination gradation was composited and analyzed for Total Petroleum Hydrocarbon (TPH) content. Vegetation data were analyzed using biotic indices such as density, Shannon-Wiener distribution index, species richness, rate of endemism, and importance value index. Potential bioindicator was analyzed by regression analysis, biplot, and IndVal. The results showed spatial variations in colonization, diversity, and structure of pioneer plants along the gradation of oil contamination. Species from the Cyperaceae, notably Scleria sumatrensis, Cyperus rotundus, and Fimbristylis ovata, were found in the center of the contamination area and resistant to oil contamination. The regression and biplot analysis revealed that along with the increasing soil TPH, the species richness and diversity index tended to decline, but the rate of endemism increased. IndVal analysis showed that C. rotundus and S. sumatrensis showed a potential bioindicators of oil-contaminated soils with TPH content of 2,700 to 3,300 ppm, while F. ovata, Panicum repens, and Imperata cylindrica was potential for TPH 692 to 851 ppm. Mimosa pudica was a sensitive plant and found on the soil TPH 73 ppm.

Efficacy of E-Safe Product in Decontamination of Hydrocarbon Contaminated Soil

Effectiveness of E-safe© product in the recovery of soil contaminated with total petroleum hydrocarbon (TPH) was investigated at the Teaching and Research Laboratory of the Department of Microbiology, Hezekiah University, Umudi, Imo State. The study was conducted on soil sample collected from aged crude oil polluted site in Rivers State.The top soil (0-30cm) was sieved using a 5mm mesh to remove gravel and debris prior to analysis. The pH, Phosphate, Nitrate, and TPH levels in the soil were analyzed using well established standard analytical protocols. E-safe product was artificially spiked in each of the 4kg soil at 0 ml, 6 ml, 12 ml, 24 ml, and 48 ml and arranged in a Completely Randomized Design. The percentage degradation of TPH in soil was monitored for a period of four (4) weeks. Results obtained showed that the soil pH was slightly acidic to basic. The findings showed Nitrate (4.97 – 24.42 ppm) and phosphate (0.134 – 0.53 ppm) ranges for both treated and control soils within the period. About 88.41% TPH degradation was achieved at 48 ml followed by 24 ml (75.63%) while the least percentage removal of TPH was recorded in the control (2.30%). The study further showed that soils contaminated with petroleum hydrocarbon altered soil physicochemistry, but more than 50% of the polluted soils were recovered by treatment with E-safe product at 48 ml, 24 ml and 12 ml respectively. The mineral components of the E-safe product could have acted as effective substance in the total removal of oil contaminants in the contaminated soil.

Enhanced bioremediation of oil-contaminated soil in a slurry bioreactor by H2O2-stimulation of oil-degrading/biosurfactant-generating bacteria: performance optimization and bacterial metagenomics.

Oil-contaminated soil is the main challenge for oil-rich countries, and this study aimed to investigate the performance of the H2O2-stimulated slurry bioreactor for the bioremediation of real oil-contaminated soil. The effect of biomass concentration, soil to water (S/W) ratio, slurry temperature, pH, and H2O2 concentration were optimized for the removal of total petroleum hydrocarbons (TPH) from oil-contaminated soil. TPH removal efficiency, biosurfactants production, and peroxidase and dehydrogenase activities were measured. The optimum conditions for the complete biodegradation of 32 [Formula: see text] in the slurry bioreactor during 6days were biomass of 2250mg/L, S/W ratio of 20%, the temperature of 30°C, pH of 7, and an H2O2 concentration of 120mg/L. The highest peroxidase, dehydrogenase, surfactin, and rhamnolipid formation were also obtained under optimum conditions. The results pointed out that complete biodegradation of 32g/kg of TPH in oil-contaminated soil at a short reaction time of 6days is achievable in the developed process operated under optimum conditions. The GC/FID analysis of solid and liquid phases showed that the bioprocess completely biodegraded the different TPH fractions. H2O2 efficiently stimulated the biosurfactant-generating bacteria to produce peroxidase and thereby accelerating the bioremediation rate. Accordingly, an H2O2-mediated slurry bioreactor inoculated with biosurfactant/peroxidase-generating bacteria is a promising technique for cleaning up oil-contaminated soils.

Fast biodegradation of long-chain alkanes in heavily polluted soil by improving C/H conversion after pre-oxidation

This study aimed to explore the effects of Fenton pre-oxidation under different conditions on the indigenous bacterial communities and the mechanism of soil C/H conversion and rapid degradation of long-chain alkanes. The soil total petroleum hydrocarbons (TPH) content for this study was 27998 ± 883 mg/kg of soil. The results showed that the half-life period of the rapid long-chain degradation group was 266 days faster than that of the slow long-chain degradation group. After pre-oxidation, the number of bacteria in the fast group (5.07 log CFU/g) was higher than slow group (2.57 log CFU/g). Further studies showed that the consumption of ammonia nitrogen in the long-chain rapid degradation group was 1.37 times higher than that in the long-chain slow degradation group. The mapping characterization by DEEM revealed a high level of humic acid-like and organic matter produced by microbial metabolism in the fast group, and the long-chain degradation group had higher C/H conversion (35%), thus improving the degradation rate of long-chain alkanes (47%). High biomass and ammonia nitrogen consumption promoted higher C/H conversion. After proper pre-oxidation, the bacterial community changed, with an average relative abundance of 34% for Actinobacteria. This study has good engineering application value.

Study on the Enhanced Remediation of Petroleum-Contaminated Soil by Biochar/g-C3N4 Composites.

This work developed an environmentally-friendly soil remediation method based on BC and g-C3N4, and demonstrated the technical feasibility of remediating petroleum-contaminated soil with biochar/graphite carbon nitride (BC/g-C3N4). The synthesis of BC/g-C3N4 composites was used for the removal of TPH in soil via adsorption and photocatalysis. BC, g-C3N4, and BC/g-C3N4 have been characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface area analyzer (BET), FT-IR, and X-ray diffraction (XRD). BC/g-C3N4 facilitates the degradation due to reducing recombination and better electron-hole pair separation. BC, g-C3N4, and BC/g-C3N4 were tested for their adsorption and photocatalytic degradation capacities. Excellent and promising results are brought out by an apparent synergism between adsorption and photocatalysis. The optimum doping ratio of 1:3 between BC and g-C3N4 was determined by single-factor experiments. The removal rate of total petroleum hydrocarbons (TPH) by BC/g-C3N4 reached 54.5% by adding BC/g-C3N4 at a dosing rate of 0.08 g/g in a neutral soil with 10% moisture content, which was 2.12 and 1.95 times of BC and g-C3N4, respectively. The removal process of TPH by BC/g-C3N4 conformed to the pseudo-second-order kinetic model. In addition, the removal rates of different petroleum components in soil were analyzed in terms of gas chromatography–mass spectrometry (GC-MS), and the removal rates of nC13-nC35 were above 90% with the contaminated soil treated by BC/g-C3N4. The radical scavenger experiments indicated that superoxide radical played the major role in the photocatalytic degradation of TPH. This work definitely demonstrates that the BC/g-C3N4 composites have great potential for application in the remediation of organic pollutant contaminated soil.

A Review of Techniques for the Determination of Total Petroleum Hydrocarbons in Soils

The Total Petroleum Hydrocarbon (TPH) is the total of different types of hydrocarbons in the crude oil mixture. It includes volatile petroleum hydrocarbons and extractable petroleum hydrocarbons. The TPH determination techniques are primarily grouped into spectroscopic (ultraviolet spectroscopy, raman spectroscopy, fluorescence spectroscopy, infrared spectroscopy) and non- spectroscopic (gravimetric, immunoassay, gas chromatography with mass spectrometric detection (GC/MSD), gas chromatography with flame ionization detection (GC-FID)) techniques. Solvent and the sample characteristics determine the efficiency of the techniques. This paper compares spectroscopic (fourier transform infrared spectroscopy and ultraviolet spectroscopy) and non-spectroscopic (gravimetric and gas chromatography) methods in the determination of TPH in soil. Spectroscopic and non-spectroscopic techniques are efficient, but the paper recommends spectroscopic techniques because the techniques are efficient with small operational time, and are safer in occupational health and safety issues. In addition their results are accurate and reliable.

Petroleum‐contamination drives the shift of microbiome through modifying soil metallome

AbstractSoil oil‐pollution is one of the most severe environmental issues at present. Shifts of soil metallome and microbiome are essential indicators for risk assessment and remediation of field soil pollutions. However, how soil metallome and microbiome react to petroleum‐contamination is not well studied. In this research, soil samples were collected from a short‐term and long‐term petroleum‐contaminated oil field. The soil physicochemical properties, metallome, microbiome, and soil microbial networks were investigated. Results showed that the contents of soil total petroleum hydrocarbon, total carbon, total nitrogen, total sulfur, total phosphorus, calcium, copper, manganese, lead, and zinc were increased by petroleum‐contamination because petroleum is rich in these elements. In contrast, the soil pH was lowered resulting from soil sulfur oxidation regardless of the petroleum pollution duration. Petroleum‐contamination also reduced bacterial and fungal α‐diversity indices because of the selective pressure of petroleum. Furthermore, bacterial α‐diversity was negatively correlated with soil total petroleum hydrocarbon content and electrical conductivity, and fungal α‐diversity was negatively correlated with soil electrical conductivity. Moreover, the relative abundances of Proteobacteria, Ascomycota, Oleibacter, and Fusarium in soil were increased by petroleum‐contamination. Network analysis showed that number of links, modules, and the network invulnerability decreased in short‐term contaminated soil, followed by the long‐term contaminated group, and the main reason should be the environmental disturbance caused by petroleum‐contamination. These results demonstrate that short‐term heavy petroleum contamination can cause shifts in soil physicochemical properties, metallome, and microbiome and assemble a less complex and vulnerable soil microbial network. Moreover, natural restoration can hardly amend soil properties and microbial network structure. This research emphasizes that the uncommonly studied soil metallome may play a vital part in the reaction of microbial communities to petroleum‐contamination.

The effect of different in situ chemical oxidation (ISCO) technologies on the survival of indigenous microbes and the remediation of petroleum hydrocarbon-contaminated soil

This study determines the effect of different in situ chemical oxidation (ISCO) technologies on soil microorganisms and total petroleum hydrocarbon (TPH) degradation. Permanganate is a moderate oxidant to the intrinsic microbes while persulfate causes severe bacterial death. TPH removal in the persulfate and permanganate systems is similar, which is higher than that in the hydrogen peroxide system. Permanganate is the most suitable oxidant for ISCO, followed by in situ bioremediation because of its persistence and low toxicity. Chemical oxidation dominates the removal of TPH throughout the experiment in the persulfate systems and during the initial stage in the hydrogen peroxide and permanganate systems. The toxicity of different catalysis/activation methods to in situ microbes decreases in the order: heat> Fe2+/citric acid> Fe2+>no catalysis/activation. If ferrous iron or citric acid is used to catalyze hydrogen peroxide, the pH must be controlled to prevent severe damage to the microbes. There is more dissolved organic carbon in solution in oxidation systems, which shows that the addition of an oxidant increases the solubility and bioavailability of the contaminant. Petroleum degraders are present in the contaminated soil and the addition of oxidants changes indigenous bacterial communities significantly.

Synergetic effects of microbial-phytoremediation reshape microbial communities and improve degradation of petroleum contaminants

Microbial-phytoremediation is an effective bioremediation technology that introduces petroleum-degrading bacteria and oil-tolerant plants into oil-contaminated soils in order to achieve effective degradation of total petroleum hydrocarbons (TPH). In this work, natural attenuation (NA), microbial remediation (MR, using Acinetobacter sp. Tust-DM21), phytoremediation (PR, using Suaeda glauca), and microbial-phytoremediation (MPR, using both species) were utilized to degrade petroleum hydrocarbons. We evaluated four different biological treatments, assessing TPH degradation rates, soil enzyme activities, and the structure of microbial community in the petroleum-contaminated soil. This finding revealed that the roots of Suaeda glauca adsorbed small amounts of polycyclic aromatic hydrocarbons, causing the structure of soil microbiota community to reshape. The abundance of petroleum-degrading bacteria and plant growth-promoting rhizobacteria (PGPR) has increased, as has microbial diversity. According to correlation research, these genera increased soil enzyme activity, boosted the number of degradation-functional genes in the petroleum hydrocarbon degradation pathway, and accelerated the dissipation and degradation of TPH in petroleum-contaminated soil. This evidence contributes to a better understanding of the mechanisms involved in the combined microbial-phytoremediation strategies for contaminated soil, specifically the interaction between microflora and plants in co-remediation and the effects on the structural reshaping of rhizosphere microbial communities.

Assessment of Ni Toxicity to Fungi and Bacteria in Oil Tainted Soils in Greater Port Harcourt Area, Nigeria

&#x0D; &#x0D; &#x0D; Intensified urbanization and industrialization are rapidly triggering the release of pollutants to the environment. This study determined the extent of soil contamination with Nickel (Ni) in oil mining areas and its effect on the levels of Ni tolerance by fungi and bacteria. The total CFUs/g of soil were enumerated after a culture period of 7 days at 28°C and LC50 was determined using probit and regression analysis. The mean values of Ni were 1.38±0.23 in industrial area, 1.41±0.36 ppm in agricultural area and 1.02±0.64 in urban area. The mean values of Total Petroleum Hydrocarbon (TPH) were 4,405.46 ppm in industrial area, 55.65 ppm in agricultural area and 1,304.53 ppm in urban area. Nickel’s peak concentration indicating growth of both fungi and bacteria at 150 ppm. There was significant difference (p ≤ 0.000) in the mean levels of LC50 for fungi among the study sites. There was no significant correlation between the concentration of TPH in soil and LC50 of fungi (r = -0.169) and bacteria (r = 0.042). In conclusion, TPH influenced the levels of fungi and bacteria tolerance to Ni in soils. Moreover, it was observed that LC50 can be a reliable method for monitoring chemically resistant microorganisms directly in the environment to improve the use of microorganisms for the bioremediation of oil contaminated soils and in monitoring of antibiotic resistant microorganisms in natural ecosystems.&#x0D; &#x0D; &#x0D;