Oil-contaminated Soil Research Articles

Complex Restoration of Oil-Contaminated Soils with New Organomineral Reagents

Among pollutants, petroleum hydrocarbons are recognized as the priority pollutants of the environment. Petroleum hydrocarbons can cause changes in the physical and chemical properties of soils, leading to a decrease in the functional activity of the microbiota of soil biocenoses. The aim of the study was to develop ways and methods of oil-contaminated soil remediation with the new generation sorbents based on organomineral biofertilizer “Kazuglegumus” and aluminum alloys activated by indium, gallium, and tin. The structure and composition of the organomineral reagents, as well as soils with different degrees of contamination were proved by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, and thermogravimetry. As a working hypothesis, it was accepted that the aluminum alloy activated by gallium, indium, and tin forms complex compounds with humic or fulvic acids, which are low-toxic or non-toxic for plants. The efficiency of cleaning oil-contaminated soils with organomineral sorbents was evaluated. The reduction of oil concentration in soil samples by 12–22% depending on the concentration of reagents and oil content in soil was revealed. The character of oil pollution impact on plants of legume families alfalfa, melilot, and sainfoin, which are characterized by the ability to accumulate and then give nitrogen to the soil, was studied. The phytotoxicity of uncontaminated and non-oil-contaminated soils was studied in laboratory and field conditions. Significantly accelerated plant growth was observed in samples of oil-contaminated soil after treatment with sorbent based on activated aluminum alloy Rau-85 and fertilizer “Kazuglegumus”. The plants had stronger root systems. These experiments are explained by the effect of Rau-85 alloys in favor of reducing the oil concentration to the normalized limits, as well as the transformation of natural humic substances and additionally applied fertilizer “Kazuglegumus” (potassium humates), which increased their biological activity.

Study on the mechanism promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface.

The Fenton method to remediate oil-contaminated soils has long suffered from low utilization of ·OH, resulting in waste of costs during practical application. This study investigated the efficient utilization of ·OH in oxidation using three different soils contaminated with oil (S1, S2, and S3). The mechanisms of promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface were studied. These results (take S1 as an example) showed that the average ·OH utilization rate of oxidized long-chain alkanes (Ka) at the solid-liquid interface reached 88.34 (mg/kg∙(a.u.)), which was higher than the non-solid-liquid interface stage (I: 54.02 (mg/kg∙(a.u.)), II: 67.36 (mg/kg∙(a.u.))). Meanwhile, the average oxidation of long-chain alkanes could increase unit ·OH intensity added (Kb) in the solid-liquid interface (990.00 mg/kg), which was much higher than Kb of the non-solid-liquid interface stage (I: 228.34 mg/kg, II: -1.48 mg/kg). Furthermore, there was a significant correlation between the proportion of humic acid-like in soil organic matter and the oxidation of long-chain alkanes at the solid-liquid interface. Thus, the surfactant-like substance generated during oxidation promoted the oxidation of long-chain alkanes at the solid-liquid interface. Moreover, when the surfactant-like substance had a matching degree (φ) with the long-chain alkanes (S1 0.18, S2 0.15, and S3 0.25), the efficiency of the ·OH utilization reached the peak, and the direct oxidation of long-chain alkanes at the solid-liquid interface was finally achieved (S1: 1373.00 mg/kg, S2: 1473.18 mg/kg, and S3: 1034.37 mg/kg). The appropriate surfactant-like substance agents in the construction can reduce the dosing of H2O2 and the construction costs by improving the efficient utilization of ·OH. Study on the mechanism promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface.

Effect of Oil Pollution on Soil Microorganisms and Plants Lepidium Sativum

The impact of oil on soil microorganisms and watercress plants was assessed. Changes in the structure of the microbial community in oil-contaminated soils and morphological and physiological parameters of watercress plants are shown. It was revealed that high concentrations of oil in the soil lead to serious disturbances of the microbial community and inhibition of biochemical processes in plants, which is confirmed by the inhibition of the growth and development of watercress plants. However, low concentrations of petroleum oil, on the contrary, stimulate the growth of watercress plants. It is concluded that the presented experiments are necessary for the purpose of full and versatile testing of the toxicity of petroleum products on various living organisms and analysis of the nature of their responses.

Integrated physiological characteristics and temporal transcriptomic analysis reveal the molecular mechanism of Pseudomonas aeruginosa degrading diesel stimulated by extracellular metabolites of euglena

Diesel pollution poses a serious threat to the ecological environment. Adding environmentally friendly biostimulants to enhance the metabolic function of indigenous microorganisms is currently a preferred strategy to improve remediation efficiency. In this study, cell morphology, physiological characteristics, and molecular level analysis of Pseudomonas aeruginosa LNR1, which was screened from oil-contaminated soil and has a diesel degradation effect, were investigated to elucidate the stimulus mechanisms by which extracellular metabolites of euglena (EME) acting as a biostimulant. The electron microscopy results indicated that EME could restore the bacterial morphological structure. Physiological analysis revealed that EME not only promoted bacterial proliferation and the secretion of extracellular proteins and polysaccharides, but also enhanced electron transfer activity and ATP content. Genomic indicated that strain LNR1 had the potential to degrade diesel efficiently. Transcriptome analysis showed that the stimulating effect of EME on strain LNR1 was distinction at different degradation time points. The initial degradation stage mainly affected the decomposition of polysaccharide and detoxification, while the active degradation stage mainly induced biochemical metabolic processes, such as amino acids and organic substrates. In particular, the expression of a series of functional genes related to pollutant emulsion adsorption, transmembrane transport, signal transduction (quorum sensing, two-component system, chemotactic system) and degradation genes was up-regulated. This study comprehensively revealed the mechanisms by which the biostimulant EME enhanced diesel degradation in strain LNR1 from multiple perspectives. It provides theoretical guidance for the practical application of EME in bioremediation, offering significant societal and economic benefits.

Characterization and Remediation Potential of Sorghum and Rice Straw-Derived Biochars on Incubated Spent-Oil Contaminated Soil

The volume and spread of spent lubricants that are indiscriminately let into the environment in developing countries are prohibitive for soil health and productivity, adversely altering soil structure, permeability and microbiota. These result to loss of arable lands and low vegetation cover, thereby contributing significantly to food insecurity and global warming. Biochars possess sustainable soil amendment potentials that depend on the choice of feedstocks. This study used suitable analytical techniques to characterize biochars derived from sorghum and rice straw after slow pyrolysis at 550°C for three hours and investigated their effects on the physicochemical properties of spent oil-contaminated soil in an incubation experiment. Both sorghum biochar (SB) and rice biochar (RB) have pH in the alkaline range (˃ 8.0), similar O/C ratio (0.24), and significant proportions of carbon (53.87–57.57%). Scanning electron microscopy of SB and RB surfaces revealed presence of porous structures. Fourier Transform Infrared Spectroscopy revealed presence of carboxyl, hydroxyl, halogens, and sulphur on the surfaces of SB and RB which are responsible for heavy metal adsorption. Compared with control, increasing biochar amendment at 1, 2 and 3% significantly increased the porosity, water holding capacity and pH of the soil. Besides, soil Fe increased while the extractable content of heavy metals decreased. From this study, the properties of SB and RB and corresponding application in spent oil-contaminated soil indicate their suitability for soil enrichment and amendment.

Metagenomic analysis of petroleum biodegradation coupled to specific N-cycling process in oil-contaminated soil

With the increased soil contamination by crude oil, understanding the effects on the metabolic potential of petroleum hydrocarbons (PHs) as well as its coupling to nitrogen-cycling (N-cycling) is crucial for improving the efficiency of in-situ bioremediation. Chemical measurements combined with metagenomic sequencing were used to investigate soils with different oiling intensity in coastal area. We suggested that oil contamination exerted strong impacts on soil properties with increased ammonium but decreased nitrite and nitrate concentrations. Taxonomic analysis revealed that oil contamination molded a unique microbial community structure with a bias towards the PHs-degrading specific populations with halophilic and oligotrophic characteristics. Alcanivorax, Marinobacter and some other potential PHs degraders were also nitrate reducing bacteria, and thus involved in both PHs biodegradation and N-cycling pathways. Microbial community structure was mainly explained by soil C/N ratio based on redundancy analysis (RDA) results. Further, functional metagenomics demonstrated that the genetic potential of PHs oxidation as well as dissimilatory nitrate reduction to ammonium (DNRA) and N-fixation was activated by oil contamination. Overall, metagenomic results in conjunction with co-occurrence network demonstrated that PHs oxidation probably coupled to DNRA, N-fixation and N-immobilization in the contaminated soil. PHs biodegradation was coupled to DNRA by the electrons transfer to nitrate/nitrite. Ammonium accumulated through N-fixation and DNRA processes could be utilized by PHs-degrading heterotrophs through N-immobilization, which was another way that connected to PHs biodegradation.

Artificial Olfactory System for Distinguishing Oil-Contaminated Soils

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

Utilization of Crude Oil-Contaminated Soil as a Foundation Base for Structures (Roads and Buildings in the Oil-Polluted Region)

The study was conducted to determine the suitability of crude oil-contaminated laterite (soil) as foundation base for roads and buildings. The laterite was sourced and uniformly mixed with different proportions of crude oil (0%, 2%, 4%, 6%, 8%, and 10%) by weight. The geotechnical properties of the contaminated laterite were determined following British standard. The properties are Atterberg limits, compaction, California Bearing Ratio (CBR), and shear strength. The results obtained were compared with those of uncontaminated laterite (0% crude oil). The results showed an initial increase in the maximum dry density and CBR at 2% contamination and thereafter significantly decreased. The shear strength increased from 72.4kN/m2 at 0% to 78.6kN/m2 at 2% crude oil and thereafter decreased. Therefore, the presence of crude oil in a small proportion (not greater than 2% of soil weight) has no adverse effect on the soil’s geotechnical properties, and as such the soil can serve as a foundation base for roads and structures.

Advancing biodegradation of petroleum contaminants by indigenous microbial consortia through assembly strategy innovations

Our demand for petroleum has challenged Earth's ecosystems, causing extensive water and soil pollution. Petroleum contamination treatment technology has relied on a range of biochemical processes to treat hydrocarbon-contaminated wastes, of which microbial degradation is one of the most economical and ecological. Engineered microbialconsortia can solve complex and difficult-to-degrade contaminants. However, the functional stability of consortia is challenged during long-term co-cultivation. Here, we introduced a novel strategy to design a stable consortium for degrading hydrocarbon pollutants, developed from ecological coexistence theory and trait-based method. Specifically, the degradation rate of the consortium constructed using the five strains was 31.54% higher than that of a single strain in a 6% (m/v) petroleum concentration after 16 days of co-culture. Besides, molecular characterization of the composition and transformation of petroleum-based substances further reveals the functional stability of consortium and the degradation mechanism and pattern of hydrocarbons by the consortium. Two independent soil experiments showed that the treatment of oil-contaminated soil by consortia from the indigenous microbiota maximizes the removal of hydrocarbon contaminants. Collectively, this strategy is generally applicable, facilitates the design of engineered microbial consortia, and provides a foundation for solving environmental pollution.

Rhamnolipid production by Pseudomonas aeruginosa (SSL-4) on waste engine oil (WEO): Taguchi optimization, soil remediation, and phytotoxicity investigation

ABSTRACT Environmental concerns and rising biosurfactant demand emphasize the need for this study. The objective is to maximize rhamnolipid-biosurfactant production by Pseudomonas aeruginosa (SSL-4) utilizing waste engine oil (WEO) as the sole substrate for use in soil bioremediation and commercial production. Using an L16 Taguchi orthogonal array, a signal-to-noise ratio, and an analysis of variance (ANOVA), the effects of environmental (pH, incubation temperature) and dietary parameters (carbon source concentration, carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratio) are examined. Variations of the following parameters were made within a carefully selected range: incubation temperature of 25–40℃, pH range of 5–11, WEO concentration of 1–7% (v/v), and C/N and C/P ratios of 10–40. Response variables in this batch study include surface tension reduction (mN/m), dry cell biomass (DCBM) (g/L), and rhamnolipids yield based on substrate consumption, YP/S (g/g). Rhamnolipid was synthesized under optimal conditions, providing a yield of 21.42 g/g. The oil recovery of 74.05 ± 1.481% was achieved from oil-contaminated soil at a CMC of ∼70 mg/L. FTIR, 1H NMR, and UPLC-MS techniques were utilized for the characterization of rhamnolipids, and AAS for determining heavy metals concentration in WEO and residual waste engine oil (RWEO). The Germination Index (GI) of ∼82.55% indicated no phytotoxicity associated with synthesized rhamnolipid.

Bioremediation of Oil Contaminated Soil and Restoration of Land Historically Polluted with Oil Products in the Agricultural Circuit in the Plain and Western Hills, Romania

Oil contamination in soil from a variety of sources, including accidental leaks, industrial activities, and improper waste disposal, involves disrupting ecosystems, contaminating water, harming human health, and diminishing agricultural productivity. Bioremediation is becoming the most important method accepted as a treatment for hydrocarbon-polluted soil using indigenous microbial flora, which aims to restore soils to their pre-hydrocarbon pollution characteristics. We will follow in our article to give some examples of good practices for bioremediation of oil-polluted soils in some sites in NE Romania. In a first step, all the oil extraction wells in NW Romania were mapped, both those in operation and those abandoned, reaching 695 wells. For 7 case studies, soil profiles were taken from the vicinity of the well column and from points close to it located in the well casing, for which the concentration of total petroleum hydrocarbons was determined. Using GIS spatial interpolation techniques, the theoretical concentration of petroleum hydrocarbons in the soil was determined. The polluted soil was transported to the bioremediation station, where it was exposed to bioremediation procedures, and the period and duration until the soil was brought to the accepted parameters in terms of allowable concentrations were analysed. The time required varies between 17 and 36 weeks needed for bioremediation. Following practical applications, it can be concluded that the time required for bioremediation is directly dependent on the initial concentration of pollutants and the number of chemical and physical interventions applied to the soil.

Hydrogen bond recombination regulated by strongly electronegative functional groups in demulsifiers for efficient separation of oil–water emulsions

Tight oil extraction and offshore oil spills generate large amounts of oil–water emulsions, causing serious soil and marine pollution. In such oil–water emulsions, the resin molecules are bound by π–π stacking and bind to interfacial water molecules via hydrogen bonds, which impede the aggregation between water droplets and thereby the separation of the emulsion. In this study, strongly electronegative oxygen atoms (in ethylene oxide, propylene oxide, esters, and hydroxyl groups) were introduced through poly(propylene glycol)-block-polyether and esterification with acrylic acid to attract negative charges in order to form electron-rich regions and enhance interfacial hydrogen bond recombination. The potential distribution in the demulsifier molecules and their space occupancy were regulated by the polymerization reaction to destroy the π–π stacking interaction between resin molecules. The results show that the binding energies (binding free energy and hydrogen bonding energy) of oxygen-containing demulsifier molecules with water molecules were higher than those of resin molecules with water molecules, resulting in the fission of the hydrogen bonds between resin and water molecules. The introduction of demulsifier molecules that occupied large interfacial space reduced the binding energy between resin molecules from −2176.06 to −110.00 kJ·mol−1. Noteworthy, the binding energy between demulsifier molecules and resin molecules was −1076.36 kJ·mol−1 lower than that between resin molecules (−110.00 kJ·mol−1), indicating the adsorption of the surrounding interfacial resin molecules by the demulsifier molecules and destruction of the π–π stacking between them, thus favoring the collapse of the interfacial structure of the oil–water emulsion and achieving its separation. This study provides important theoretical support for the treatment of oil-contaminated soil and offshore oil spill pollution.

БАКТЕРИИ-НЕФТЕДЕСТРУКТОРЫ С УСТОЙЧИВОСТЬЮ К ПРИСУТСТВИЮ ДОПОЛНИТЕЛЬНЫХ ПОЛЛЮТАНТОВ

Throughout the world, significant areas of agricultural land are polluted with hydrocarbons. Their microbiological purification is hampered by the presence of residual amounts of pesticides (herbicides, in particular), which inhibit the vital activity of oil-destructing bacteria. In addition, along with crude oil, heavy metals and salts (mainly chlorides) can enter arable soils, which, in turn, have a negative effect on microorganisms. Therefore, for the bioremediation of such territories, hydrocarbon-oxidizing bacteria resistant to the presence of additional pollutants should be used. In the present work, three isolates were identified that are capable of active growth in a liquid medium with oil. Using time-of-flight matrix-activated laser desorption-ionization (MALDI-TOF) mass spectrometry of the cellular protein fraction, sequencing of the nucleotide sequence of the 16S rRNA gene and phylogenetic analysis, the species of microorganisms belonging to the genus Acinetobacter was determined. The bacteria had a significant ability to biodegrade oil (71.8-74.1%), which was estimated from the degree of destruction of the aliphatic oil fraction by the gas chromatographic method after preliminary extraction with hexane. The resistance of microorganisms to the presence of herbicides, heavy metals, and sodium chloride was determined by their growth on meat-peptone agar with different concentrations of preparations, salts of these metals, or NaCl. The strains showed resistance to the presence in the medium of herbicides based on 2,4-D and imazethapyr at a concentration of 10.0 ml/l, sodium chloride in an amount of 5.0-6.0%, and lead ions (1.00-1.25 g/l). In addition, they produced lipase and were capable of fixing atmospheric nitrogen and dissolving inorganic phosphate. The last two properties are important for stimulating the growth and development of remedial plants. The obtained results indicate that all three strains have certain prospects of application for cleaning oil-contaminated agricultural soils and require further study of their biotechnological potential.

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

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

Efficient production of biosurfactant surfactin by a newly isolated Bacillus subtilis (sp.) 50499 strain from oil-contaminated soil

Biosurfactant surfactin has a high market value and broad application prospects in the food industry and various industrial fields. However, its production efficiency limits its suitability for real applications. In this study, a new Bacillus subtilis (sp.) 50499 strain was isolated from crude oil-contaminated soil and used to efficiently produce surfactin. The initial surfactin titer was 2.25 g/L after three days of fermentation. Adding 2 g/L of L-Leu significantly improved the titer to over 5.5 g/L after optimizing the culture medium at 37 °C. However, adding D-Leu had the opposite effect on surfactin production, and the surfactin titer dropped to below 0.2 g/L. Furthermore, the product of this strain was analyzed to confirm the identity of surfactin. The surfactin obtained in the present study reduced the surface tension of water to 28.6 mN/m at a critical micelle concentration of 20 mg/L. The emulsification index against n-hexane, corn, and crude oil was as high as over 90%. Hence, the present study provides a newly over-producing strain for surfactin production.

EFFECTS OF VERMICAST TEA ON THE REMEDIATION OF SPENT ENGINE OIL CONTAMINATED SOIL

The need to maintain the rising numbers of both serviceable and degenerating automobiles in Nigeria has led to the springing up of vehicle workshops in approved and unapproved locations, where mechanics discharge spent engine oil indiscriminately into the soil and water environments. It is therefore desirable to explore potentially affordable and sustainable remediation methods. This study examined the efficacy of vermicast tea for the remediation of spent engine oil contaminated soil. Spent engine oil contaminated soil was collected from an automobile workshop, and mixed with different concentrations (20%, 50%, and 100%) of vermicast tea. The total petroleum hydrocarbon (TPH), moisture content, organic matter content, pH, and cation exchange capacity (CEC) in the contaminated soils were determined on day one, day 21, and day 42, using standard procedures. It was found that the TPH concentrations reduced in both vermicast tea treated and untreated soils, but percentage reductions were higher in contaminated soils treated with vermicast tea (63.65% – 74.74%) than in soil without vermicast tea (59.85%). The moisture content, organic matter content, pH, and cation exchange capacity of the spent engine oil contaminated soil were impacted due to the presence of vermicast tea. Moreover, remediation was observed to be significantly higher (p<0.05) at day 42 of exposure to vermicast tea, than at day 21. These results imply that vermicast tea can hasten natural remediation of soil contaminated with spent engine oil. It is recommended that future studies on the use of vermicast tea to remediate spent engine oil-contaminated soil for a...

Evaluating the effectiveness of various remediation therapies on the engineering properties of oil-contaminated soils

This study was embarked upon to ascertain the effectiveness of using physical and biological remediation procedures to amend the impact of oil pollution on soil engineering properties. Soil contaminated with crude oil at a mix ratio of 20:1 (percentage by weight), was remediated with charcoal (C2), charcoal + seaweed extract + groundnut plant (C3), and charcoal + wood ash + groundnut plant (C4). During the procedure, the soil’s total petroleum hydrocarbon (TPH) level was determined through American Public Health Association (APHA) approved procedures; while the geotechnical (maximum dry density “MDD”, optimal moisture content “OMC, and California bearing ratio “CBR”) and electrical properties (electrical conductivity “EC”, dielectric constant “ɛʹ, and electrical resistivity “ρ”) were measured in accordance with American Society for Testing and Materials (ASTM) and Institute of Electrical and Electronics Engineers (IEEE) approved procedures. The results depicted that the TPH, ɛʹ and ρ-values of the contaminated soil samples declined by 56.71%, 82.01% and 72.80%; 31.65%, 36.85% and 19.92%; and 56.32%, 62.03% and 60.27%, respectively in the C2, C3 and C4 samples after the remediation program; while the soil EC increased by 103.45%, 145.68% and 135.34% in the C2, C3 and C4 samples, respectively. Likewise, the C2, C3 and C4 samples CBR, MDD and OMC values increased by 29.49%, 34.75% and 50.30%; 7.87%, 11.02% and 4.72; and 12.02%, 28.01% and 40.38%, respectively at the end of the experimental period. These findings portrayed that hybridized remediation therapies are better remediating techniques in remediating contaminated soils; hence sustaining the integrity of the soils’ geotechnical and electrical properties.

A comprehensive study on diesel oil bioremediation under microcosm conditions using a combined microbiological, enzymatic, mass spectrometry, and metabarcoding approach.

This study aims at the application of a marine fungal consortium (Aspergillus sclerotiorum CRM 348 and Cryptococcus laurentii CRM 707) for the bioremediation of diesel oil-contaminated soil under microcosm conditions. The impact of biostimulation (BS) and/or bioaugmentation (BA) treatments on diesel-oil biodegradation, soil quality, and the structure of the microbial community were studied. The use of the fungal consortium together with nutrients (BA/BS) resulted in a TPH (Total Petroleum Hydrocarbon) degradation 42% higher than that obtained by natural attenuation (NA) within 120days. For the same period, a 72 to 92% removal of short-chain alkanes (C12 to C19) was obtained by BA/BS, while only 3 to 65% removal was achieved by NA. BA/BS also showed high degradation efficiency of long-chain alkanes (C20 to C24) at 120 days, reaching 90 and 92% of degradation of icosane and heneicosane, respectively. In contrast, an increase in the levels of cyclosiloxanes (characterized as bacterial bioemulsifiers and biosurfactants) was observed in the soil treated by the consortium. Conversely, the NA presented a maximum of 37% of degradation of these alkane fractions. The 5-ringed PAH benzo(a)pyrene, was removed significantly better with the BA/BS treatment than with the NA (48 vs. 38 % of biodegradation, respectively). Metabarcoding analysis revealed that BA/BS caused a decrease in the soil microbial diversity with a concomitant increase in the abundance of specific microbial groups, including hydrocarbon-degrading (bacteria and fungi) and also an enhancement in soil microbial activity. Our results highlight the great potential of this consortium for soil treatment after diesel spills, as well as the relevance of the massive sequencing, enzymatic, microbiological and GC-HRMS analyses for a better understanding of diesel bioremediation.

Biodegradation of Waste Lubricant Oil by a Novel Isolated Biosurfactant Producer- Achromobacter xylosoxidans PSA5

Waste lubricant oil (WLO) is a critical environmental issue because of its recycle and disposal challenges. A potent biosurfactant-producing bacterial strain was isolated by the enrichment culture technique using WLO as the sole carbon source from the oil-contaminated soils. The strain was identified as Achromobacter xylosoxidans (NCBI GenBank accession number: MW673656) based on the morphological, biochemical, and 16S rRNA gene sequencing. The preliminary characterization of the produced biosurfactant by biochemical methods revealed its glycolipid nature. The strain possessed extensive biodegradative potential and degraded various components present in WLO. The gas chromatography-mass spectrometry (GC-MS) analysis showed that the strain could degrade hydrocarbons (C7-C22) and diethyl phthalate, a priority pollutant, with a relative degradation of 43.87% within 7 days of incubation. The biodegradation of WLO by the strain confers its use in the bioremediation of oil-polluted environments, and the simultaneous biosurfactant production is undoubtedly a step toward greener technology.

Photochemical mobilization of dissolved hydrocarbon oxidation products from petroleum contaminated soil into a shallow aquifer activate human nuclear receptors

Elevated non-volatile dissolved organic carbon (NVDOC) concentrations in groundwater (GW) monitoring wells under oil-contaminated hydrophobic soils originating from a pipeline rupture at the National Crude Oil Spill & Natural Attenuation Research Site near Bemidji, MN are documented. We hypothesized the elevated NVDOC is comprised of water-soluble photooxidation products transported from the surface to the aquifer. We use field and laboratory samples in combination with complementary analytical methods to test this hypothesis and determine the biological response to these products. Observations from optical spectroscopy and ultrahigh-resolution mass spectrometry reveal a significant correlation between the chemical composition of NVDOC leached from photochemically weathered soils and GW monitoring wells with high NVDOC concentrations measured in the aquifer beneath the contaminated soil. Conversely, the chemical composition from the uncontaminated soil photoleachate matches the NVDOC observed in the uncontaminated wells. Contaminated GW and photodissolution leachates from contaminated soil activated biological targets indicative of xenobiotic metabolism and exhibited potential for adverse effects. Newly formed hydrocarbon oxidation products (HOPs) from fresh oil could be distinguished from those downgradient. This study illustrates another pathway for dissolved HOPs to infiltrate GW and potentially affect human health and the environment.