Showing papers on "Total petroleum hydrocarbon published in 2020"

Rhizodegradation of Petroleum Oily Sludge-contaminated Soil Using Cajanus cajan Increases the Diversity of Soil Microbial Community

Abstract: Most components of petroleum oily sludge (POS) are toxic, mutagenic and cancer-causing. Often bioremediation using microorganisms is hindered by the toxicity of POS. Under this circumstance, phytoremediation is the main option as it can overcome the toxicity of POS. Cajanus cajan a legume plant, was evaluated as a phyto-remediating agent for petroleum oily sludge-spiked soil. Culture dependent and independent methods were used to determine the rhizosphere microorganisms’ composition. Degradation rates were estimated gravimetrically. The population of total heterotrophic bacteria (THRB) was significantly higher in the uncontaminated soil compared to the contaminated rhizosphere soil with C. cajan, but the population of hydrocarbon-utilizing bacteria (HUB) was higher in the contaminated rhizosphere soil. The results show that for 1 to 3% oily sludge concentrations, an increase in microbial counts for all treatments from day 0 to 90 d was observed with the contaminated rhizosphere CR showing the highest significant increase (p < 0.05) in microbial counts compared to other treatments. The metagenomic study focused on the POS of 3% (w/w) and based on the calculated bacterial community abundance indices showed an increase in the values for Ace, Cho, Shannon (Shannon-Weaver) and the Simpson’s (measured as InvSimpson) indices in CR3 compared to CN3. Both the Simpson’s and the Shannon values for CR3 were higher than CN3 indicating an increase in diversity upon the introduction of C. cajan into the contaminated soil. The PCoA plot revealed community-level differences between the contaminated non-rhizosphere control and contaminated rhizosphere microbiota. The PCoA differentiated the two treatments based on the presence or absence of plant. The composition and taxonomic analysis of microbiota-amplified sequences were categorized into eight phyla for the contaminated non-rhizosphere and ten phyla for the contaminated rhizosphere. The overall bacterial composition of the two treatments varied, as the distribution shows a similar variation between the two treatments in the phylum distribution. The percentage removal of total petroleum hydrocarbon (TPH) after 90 days of treatments with 1, 2, 3, 4, and 5% (w/w) of POS were 92, 90, 89, 68.3 and 47.3%, respectively, indicating removal inhibition at higher POS concentrations. As the search for more eco-friendly and sustainable remediating green plant continues, C. cajan shows great potential in reclaiming POS contaminated soil. Our findings will provide solutions to POS polluted soils and subsequent re-vegetation.

Impacts of Oil and Gas Production on Contaminant Levels in Sediments

Abstract: Recent technological progresses have unlocked tremendous shale energy resources, leading to increased production of oil and gas and a variety of new environmental pollution issues in the United States. One such example is management of produced waters, which are often disposed of via deep well injection. Produced water injection has been linked to induced seismicity. Thus, there are strong incentives for alternative management strategies that come with new, uncertain environmental risks. This paper summarizes studies of sediment pollution due to oil and gas production. The goal is to highlight potential environmental risks associated with produced water management, including long-term contamination of sediments. Sediment contaminants from produced waters include organic and inorganic toxic compounds. Three different indicators have been developed for sediment pollution: the geoaccumulation index, pollution load index, and the enrichment factor. The main pollutants in sediments resulting from oil and gas production are heavy metals, salts, naturally occurring radioactive materials (NORMs), oil and grease (O&G), benzene, toluene, ethylbenzene and xylene (BTEX), total petroleum hydrocarbon (TPH), and polycyclic aromatic hydrocarbon (PAHs). These pollutants reach sediments and water resources via pipeline leaks, truck spills, improper waste disposal, and underground injection. Methods to decrease contaminant risks in sediments include surface capping, bioremediation, and phytoremediation. The shale oil and gas boom has exacerbated produced water management issues. As states consider regulation of treated produced waters, there is a strong need to consider potential contaminants of concern. Several case studies from the U.S., Middle East, Africa, Asia, and South America were used to assess levels of contamination around the world’s sediments in regions with high levels of oil and gas activity. Appropriate management of residual pollution from oil and gas operations should consider the nature of contaminants and sediments, the routes of contamination, the levels of contamination, the effect of contaminants on the sites, and methods for contaminant cleanup.

Degradation of petroleum hydrocarbons in unsaturated soil and effects on subsequent biodegradation by potassium permanganate

Abstract: To date, the oxidation of petroleum hydrocarbons using permanganate has been investigated rarely. Only a few studies on the remediation of unsaturated soil using permanganate can be found in the literature. This is, to the best of our knowledge, the first study conducted using permanganate pretreatment to degrade petroleum hydrocarbons in unsaturated soil in combination with subsequent bioaugmentation. The pretreatment of diesel-contaminated unsaturated soil with 0.5-pore-volume (5%) potassium permanganate (PP) by solution pouring and foam spraying (with a surfactant) achieved the total petroleum hydrocarbon (TPH) removal efficiencies of 37% and 72.1%, respectively. The PP foam, when coupled with bioaugmentation foam, further degraded the TPH to a final concentration of 438 mg/kg (92.1% total reduction). The experiment was conducted without soil mixing or disturbance. The relatively high TPH removal efficiency achieved by the PP–bioaugmentation serial foam application may be attributed to an increase in soil pH caused by the PP and effective infiltration of the remediation agent by foaming. The applied PP foam increased the pH of the acidic soil, thus enhancing microbial activity. The first-order biodegradation rate after PP oxidation was calculated to be 0.068 d−1. Furthermore, 94% of the group of relatively persistent hydrocarbons (C18–C22) was removed by PP–bioaugmentation, as verified by chromatogram peaks. Some physicochemical parameters related to contaminant removal efficiency were also evaluated. The results reveal that PP can degrade soil TPH and significantly enhance the biodegradation rate in unsaturated diesel-contaminated soil when combined with bioaugmentation foam.

Performance and Kinetics of Bioaugmentation, Biostimulation, and Natural Attenuation Processes for Bioremediation of Crude Oil-Contaminated Soils

Abstract: Bioremediation of contaminated sites is usually limited due to the inadequate availability of nutrients and microorganisms. This study was conducted to assess the impact of bioaugmentation (BA) and biostimulation (BS) on petroleum hydrocarbon degradation efficiency. In addition, treatment performance and kinetics of different remediation processes were investigated. For this purpose, four tanks containing oil-contaminated soils were tested. Tank 1 was operated as the natural attenuation process. Then, a microbial inoculum and nutrients were added to tank 2 to promote BA and BS. In tank 3, only the BA process was adopted, whereas in tank 4, only the BS process was adopted. After 63 days of operation, the total petroleum hydrocarbon (TPH) in tank 2 was reduced from 1674 to 430 mg/kg, with 74% reduction. Tank 1, tank 3, and tank 4 indicated TPH reductions of 35%, 41%, and 66%, respectively. Microbiological analysis of the inoculum indicated that Alcanivorax was the dominant bacterium. The population of TPH degrader bacteria in tank 2 soil was two orders of magnitude higher than in the control tank. Reaction rate data were fitted with a first-order reaction rate model. The Monod kinetic constants, maximum specific growth rate (µmax), and substrate concentration at half-velocity constant (Ks) were also estimated. This study showed that the TPH removal efficiency in the combined BA and BS process was higher than in other processes tested. The populations of TPH degrading microorganisms in soil tanks were positively related to TPH removal efficiency during bioremediation of petroleum-contaminated soils.

Enhancing the Phytoremediation of Hydrocarbon-Contaminated Soils in the Sudd Wetlands, South Sudan, Using Organic Manure

Abstract: Phytoremediation of hydrocarbon-contaminated soils is a challenging process. In an effort to enhance phytoremediation, soil was artificially contaminated with known concentration of light crude oil containing Total petroleum hydrocarbon (TPH) at a concentration of 75 gkg−1 soil. The contaminated soil was subjected to phytoremediation trial using four plant species (Oryza longistaminata, Sorghum arundinaceum, Tithonia diversifolia, and Hyparrhenia rufa) plus no plant used as control for natural attenuation. These phytoremediators were amended with concentrations (0, 5 and 10 gkg−1 soil) of organic manure (cow dung). Results at 120 days after planting, showed that application of manure at concentrations of 5 and 10 gkg−1 soil combined with an efficient phytoremediator can significantly enhance reduction of TPH compared to natural attenuation or use of either manure or a phytoremediator alone ( ). The study also showed that a treatment combination of manure 5 gkg−1 soil, with a phytoremediator gives a similar mean percentage reduction of TPH as manure 10 gkg−1 soil ( ). Therefore, the study concludes that use of phytoremediators and manure 5 gkg−1 soil could promote the restoration of TPH contaminated-soils in the Sudd region of South Sudan.

Modeling of Azadirachta indica Leaves Powder Efficiency for the Remediation of Soil Contaminated With Crude Oil

Abstract: A regression analysis model was developed to examine the reliability and the acceptability of the sun-dried and room-dried Azadirachta indica leaves for the remediation crude oil contaminated soil in Niger Deltal, Nigeria. An experimental approach was used to monitor the concentration of the total petroleum hydrocarbon (TPH) degradation that was enhanced in the presence of the microbes in the reactor. A regression analysis was performed to evaluate the reaction behavior microbes in reactor for the remediation of the TPH in the presence of sun-dried and room-dried A. indica leaves in sandy and loamy soils contaminated with 100 ml of crude oil. The physicochemical properties of control loamy soil was as; pH (6.75), electric conductivity (10.36 µS/cm), total oxygen (2.99%), total Nitrogen (0.091%), potassium (36.82942%), phosphorus (15.36%) and total bacteria (2.15×102 cfu/g). Whereas, these values were as pH (6.82), electric conductivity (21.48 µS/cm), total oxygen content (1.18%), total nitrogen (0.036%), potassium (24.03681%), phosphorus (5.18%) and total bacteria count (1.86×102 cfu/g) for sandy soil. The inoculant was prepared by blending sun-dried and room-dried A. indica leaves. The blended A. indica leaves in 50 to 100 g range were applied on the polluted soils for 35 days and significant reduction in contaminating agents was observed. The highest remediation was observed in soils treated with 100 g room dried A. indica leaves. A 96% remediation recorded in sandy soil treated with 100 g room dried A. indica leaves as TPH depleted from 35818.69 mg/kg to 1349.109 mg/kg and 92% reduction was observed in loamy soil treated with 100 g dried A. indica leaves and TPH depleted from 48508.92 mg/kg to 3977.739 mg/kg. The regression model developed was successfully employed to predict TPH remediation behavior, which can be applied to monitor remediation of contaminated soil.

Isolation and Characterization of Hexadecane Degrading Bacteria from Oil- polluted soil in Gio Community, Niger Delta, Nigeria

Abstract: This study investigated the presence of viable indigenous hexadecane degraders in chronically polluted soil in Gio community, Niger Delta. Crude oil-polluted samples were collected from the four GPS coordinate points at depth of 0-0.15m (Gio polluted surface soil [GPS]), 1m (Gio polluted subsurface soil [GPSS]) respectively and Gio unpolluted control soil (GUPS) was collected from approximately 1000m away from the polluted site. Gas chromatography - flame ionization detector (GC-FID) analysis for total petroleum hydrocarbon (TPH) were 36,776 ppm, 14,100 ppm, 480 ppm for GPS, GPSS and GUPS respectively. Polycyclic aromatic hydrocarbon (PAHs) concentrations determined were 12,210 ppm, 3,250 ppm, 23 ppm for GPS, GPSS and GUPS respectively. Total cultivable hydrocarbon utilizing bacterial count (TCHUB) for GPS, GPSS and GUPS were 6.6 × 105cfu/g, 6.4 × 105cfu/g and 3.96 × 104cfu/g respectively. Out of the 22 bacteria isolated and characterized from the crude oil enrichment method, Pseudomonas sp. (65 %), Bacillus sp. (66%), Achromobacter sp. Proteus sp.(45%) and Serratia sp (40%). demonstrated higher biodegradation potential for hexadecane using 2,6-dichlorophenol indophenols (DCPIP) redox indicator. In conclusion the extant autochthonous bacteria are metabolically active, can effectively degrade hexadecane and could be good candidates for bioremediation.

Molecular Transformation of Crude Oil Contaminated Soil after Bioelectrochemical Degradation Revealed by FT-ICR Mass Spectrometry

Abstract: Bioremediation is a low-cost approach for crude oil spill remediation, but it is often limited by electron acceptor availability. In addition, the biodegradation products of crude oil contaminants are complex, and transformation pathways are difficult to decipher. This study demonstrates that bioelectrochemical systems (BESs) can be effective in crude oil degradation by integrating biological and electrochemical pathways, and more importantly, it provides the first understanding on the daughter products of bioelectrochemical hydrocarbon degradation. Using electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and two-dimensional gas chromatography (GC × GC), the results showed that the active BES reactor improved the total petroleum hydrocarbon (TPH) degradation by ∼70% than open circuit control reactors. After separating the daughter products into nine fractions (MA1-MA9) according to the molecular weight (m/z 200-1000) by modified aminopropyl silica (MAPS) fractionation, we found that active BES remediation resulted in 50% more polar, oxygen-containing naphthenic (NAP) acids. The MA4 fraction (centered at ∼550 Da) increased by 47%, and MA5 and MA7 fractions with higher molucular weight increased by a maximum of ∼7- and 9-fold, respectively. These results are in accordance with the variation of bulk elemental compositions in O2 species, where daughter transformation products doubled relative to parent oil extract. The contribution of newly generated NAP acids was mainly from higher-order oxygen species (O5-O6) with increased hydrophobicity in conjunction with a decreased abundance in lower-order oxygen species (O1). Overall, the study suggests that n-alkane degradation occurred via β-oxidation to oxygenated transformation products with lower molecular weight, such as n-alcohols in O1 class and subsequently to n-fatty acids in O2 class.

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Abstract: Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient (0–0.4043 g/g) in surface (5–10 cm) and subsurface (35–40 cm) petroleum-contaminated soil samples from the Dagang Oilfield, China. Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods, the bacterial diversity of the soil was studied. Subsequently, the environmental parameters were measured to analyze its relationship with the community variation. Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils, but no differences were observed in different depths of petroleum-contaminated soil. Meanwhile, many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties. Total petroleum hydrocarbon, total organic carbon, and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils. Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Impact of necrophytoremediation on petroleum hydrocarbon degradation, ecotoxicity and soil bacterial community composition in diesel-contaminated soil.

Abstract: Hydrocarbon degradation is usually measured in laboratories under controlled conditions to establish the likely efficacy of a bioremediation process in the field. The present study used greenhouse-based bioremediation to investigate the effects of natural attenuation (NA) and necrophytoremediation (addition of pea straw (PS)) on hydrocarbon degradation, toxicity and the associated bacterial community structure and composition in diesel-contaminated soil. A significant reduction in total petroleum hydrocarbon (TPH) concentration was detected in both treatments; however, PS-treated soil showed more rapid degradation (87%) after 5 months together with a significant reduction in soil toxicity (EC50 = 91 mg diesel/kg). Quantitative PCR analysis revealed an increase in the number of 16S rRNA and alkB genes in the PS-amended soil. Substantial shifts in soil bacterial community were observed during the bioremediation, including an increased abundance of numerous hydrocarbon-degrading bacteria. The bacterial community shifted from dominance by Alphaproteobacteria and Gammaproteobacteria in the original soil to Actinobacteria during bioremediation. The dominance of two genera of bacteria, Sphingobacteria and Betaproteobacteria, in both NA- and PS-treated soil demonstrated changes occurring within the soil bacterial community through the incubation period. Additionally, pea straw itself was found to harbour a diverse hydrocarbonoclastic community including Luteimonas, Achromobacter, Sphingomonas, Rhodococcus and Microbacterium. At the end of the experiment, PS-amended soil exhibited reduced ecotoxicity and increased bacterial diversity as compared with the NA-treated soil. These findings suggest the rapid growth of species stimulated by the bioremediation treatment and strong selection for bacteria capable of degrading petroleum hydrocarbons during necrophytoremediation.

Biological Effects of Hydrocarbon Degradation Intermediates: Is the Total Petroleum Hydrocarbon Analytical Method Adequate for Risk Assessment?

Abstract: In crude oil contaminant plumes, the dissolved organic carbon (DOC) is mainly hydrocarbon degradation intermediates only partly quantified by the diesel range total petroleum hydrocarbon (TPHd) method. To understand potential biological effects of degradation intermediates, we tested three fractions of DOC: (1) solid-phase extract (HLB); (2) dichloromethane (DCM-total) extract used in TPHd; and (3) DCM extract with hydrocarbons isolated by silica gel cleanup (DCM-SGC). Bioactivity of extracts from five wells spanning a range of DOC was tested using an in vitro multiplex reporter system that evaluates modulation of the activity of 46 transcription factors; extracts were evaluated at concentrations equivalent to the well water samples. The aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) transcription factors showed the greatest upregulation, with HLB exceeding DCM-total, and no upregulation in the hydrocarbon fraction (DCM-SGC). The HLB extracts were further studied with HepG2 chemically activated luciferase expression (CALUX) in vitro assays at nine concentrations ranging from 40 to 0.01 times the well water concentrations. Responses decreased with distance from the source but were still present at two wells without detectable hydrocarbons. Thus, our in vitro assay results indicate that risks associated with degradation intermediates of hydrocarbons in groundwater will be underestimated when protocols that remove these chemicals are employed.

Kinetic modelling of total petroleum hydrocarbon in spent lubricating petroleum oil impacted soil under different treatments

Abstract: The integration of first and second order kinetic model in parameter estimation for the degradation pattern of total petroleum hydrocarbon (TPH) in spent lubricating petroleum oil (SLPO) over a fou...

The oil removal and the characteristics of changes in the composition of bacteria based on the oily sludge bioelectrochemical system.

Abstract: Microbial fuel cell (MFC) technology is a simple way to accelerate the treatment of the oily sludge which is a major problem affecting the quality of oil fields and surrounding environment while generating electricity. To investigate the oil removal and the characteristics of changes in the composition of bacteria, sediment microbial fuel cells (SMFCs) supplemented with oily sludge was constructed. The results showed that the degradation efficiency of total petroleum hydrocarbon (TPH) of SMFC treatment was 10.1 times higher than the common anaerobic degradation. In addition, the degradation rate of n-alkanes followed the order of high carbon number > low carbon number > medium carbon number. The odd-even alkane predominance (OEP) increased, indicating that a high contribution of even alkanes whose degradation predominates. The OUT number, Shannon index, AEC index, and Chao1 index of the sludge treated with SMFC (YN2) are greater than those of the original sludge (YN1), showing that the microbial diversity of sludge increased after SMFC treatment. After SMFC treatment the relative abundance of Chloroflexi, Bacteroidia and Pseudomonadales which are essential for the degradation of the organic matter and electricity production increased significantly in YN2. These results will play a crucial role in improving the performance of oily sludge MFC.

Biodegradation of Total Petroleum Hydrocarbons in Soil: Isolation and Characterization of Bacterial Strains from Oil Contaminated Soil

Abstract: In this study, we isolated seven strains (termed BY1–7) from polluted soil at an oil station and evaluated their abilities to degrade total petroleum hydrocarbons (TPHs) Following 16 rRNA sequence analysis, the strains were identified as belonging to the genera Bacillus, Acinetobacter, Sphingobium, Rhodococcus, and Pseudomonas, respectively Growth characterization studies indicated that the optimal growth conditions for the majority of the strains was at 30 °C, with a pH value of approximately 7 Under these conditions, the strains showed a high TPH removal efficiency (50%) after incubation in beef extract peptone medium for seven days Additionally, we investigated the effect of different growth media on growth impact factors that could potentially affect the strains’ biodegradation rates Our results suggest a potential application for these strains to facilitate the biodegradation of TPH-contaminated soil

Bioremediation of in-situ crude oil contaminated soil using selected organic dung

Abstract: The potential of cow, pig and poultry dung for the bioremediation of in-situ crude oil contaminated soil for a period of 3-15 days at different soil and dung ratios were the objectives of this investigation. Using simulated soil, 200 g were measured into polyethylene bags labelled A,B,C,D,E, F and G. Soil physicochemical parameters such as particle size distribution, pH, organic carbon, organic matter, nitrogen and phosphorus were analysed using standard methods. Total Petroleum Hydrocarbon (TPH) concentrations were analyzed using spectrophotometry method at 420 nm. The concentrations of TPH decreased progressively with an increase in dung and time in the order cow dung > pig dung > poultry dung except the control soil that showed slight TPH reduction. Results also show that biostimulant efficiency (BE) increases with increase in dung and reduces with time. Results also reveal that dung with high bioremediation constant recorded a corresponding short half-life. Results show that there is a significant difference (P 0.05) in amended soil and time for poultry dung except for cow and pig dung. This study has shown that cow dung is more effective in bioremediation of TPH in crude oil contaminated soil.

Comparative study on multiway enhanced bio- And phytoremediation of aged petroleum-contaminated soil

Abstract: Bioremediation and phytoremediation of soil polluted with petroleum hydrocarbons (PHs) are an effective and eco-friendly alternative to physicochemical methods of soil decontamination These techniques can be supported by the addition of effective strains and/or surface-active compounds However, to obtain maximum efficacy of bioremediation, the interactions that occur between the microorganisms, enhancement factors and plants need to be studied Our study aimed to investigate the removal of petroleum hydrocarbons from an aged and highly polluted soil (hydrocarbon content about 25%) using multiway enhanced bio- and phytoremediation For this purpose, 10 enhanced experimental groups were compared to two untreated controls Among the enhanced experimental groups, the bio- and phytoremediation processes were supported by the endophytic strain Rhodococcus erythropolis CDEL254 This bacterial strain has several plant growth-promoting traits and can degrade petroleum hydrocarbons and produce biosurfactants Additionally, a rhamnolipid solution produced by Pseudomonas aeruginosa was used to support the total petroleum hydrocarbon loss from soil After 112 days of incubation, the highest PH removal (311%) was observed in soil planted with ryegrass (Lolium perenne L cv Pearlgreen) treated with living cells of the CDEL254 strain and rhamnolipid solution For non-planted experimental groups, the highest PH loss (261%) was detected for soil treated with heat-inactivated CDEL254 cells and a rhamnolipid solution In general, the differences in the efficacy of the 10 experimental groups supported by plants, live/dead cells of the strain tested and rhamnolipid were not statistically significant However, each of these groups was significantly more effective than the appropriate control groups The PH loss in untreated (natural attenuation) and soils that underwent phytoremediation reached a value of 142% and 174%, respectively Even though the CDEL254 strain colonized plant tissues and showed high survival in soil, its introduction did not significantly increase PH loss compared to systems treated with dead biomass These results indicate that the development of effective biological techniques requires a customized approach to the polluted site and effective optimization of the methods used

Synergistic Effect of Rhamnolipids and Inoculation on the Bioremediation of Petroleum-Contaminated Soils by Bacterial Consortia

Abstract: Crude oil is a serious soil pollutant, requiring large-scale remediation efforts. Bacterial consortia in combination with rhamnolipids can be an effective bioremediation method. However, the underlying mechanisms and associated changes in soil bacterial composition remain uncharacterized. Therefore, this study sought to evaluate the effectiveness of rhamnolipids in petroleum hydrocarbon removal, and the associated bacterial community dynamics during bioremediation of petroleum-contaminated soils. Contaminated soils were subjected to natural attenuation, bioremediation with rhamnolipids, bioremediation with bacterial consortia, or bioremediation with bacterial consortia supplemented with rhamnolipids (BMR). High-throughput sequencing of bacterial sample partial 16S rRNA sequences was performed. Additionally, the n-alkanes and aromatic fractions were analyzed by gas chromatography-mass spectroscopy. The results showed that rhamnolipid supplementation increased the rate and extent of total petroleum hydrocarbon biodegradation to a maximum of 81% within 35 days. Further, phylogenetic analysis revealed that the bacterial community was composed of 14 phylotypes (similarity level = 97%). Actinobacteria and Proteobacteria were the two core phyla in all samples, accounting for 63–89%, but Proteobacteria was the most dominant phylum in the BMR sample (~ 53%). Among the top 20 genera, Pseudomonas, Pseudoxanthomonas, Cavicella, Mycobacterium, Rhizobium, and Acinetobacter were more abundant in BMR samples compared to other samples. Predicted functional profiles revealed that rhamnolipid addition also induced changes in gene abundance related to hydrocarbon metabolic pathways. This study provided comprehensive insights into the synergistic effect of rhamnolipids and bacterial consortia for altering bacterial populations and specific functional traits, which may serve to improve bacteria-mediated petroleum hydrocarbon biodegradation in contaminated soils.

Arid ecosystem resilience to total petroleum hydrocarbons disturbance: A case‐study from the State of Kuwait associated with the Second Gulf War

Abstract: The world's largest hydrocarbon disturbance occurred in the deserts and offshore waters of Kuwait during the Second Gulf War in 1990–1991. In this research, remote sensing (RS) and geographic information system (GIS) techniques were utilized to explore how native desert vegetation has recovered from hydrocarbon contamination after the Second Gulf War. By using RS techniques, change detection analysis was conducted to understand the changes about the coverage and extent of the total petroleum hydrocarbon (TPH) contamination and vegetation recovery. These changes were traced from 1991 until the hydrocarbon was no longer visible on the ground surface in 1998. GIS spatial analysis was conducted to determine the major ecosystem factors that influenced the vegetation recovery along with the removal of hydrocarbon disturbance. According to the results, autogenic recovery occurred at both sites within a few years and that desert native vegetation was found to have the ability to adapt and recover from hydrocarbon pollution. Native vegetation recovered across 31% of the TPH‐contaminated areas at Umm Gudair and 34% at Wadi Al Batin. The changes in TPH contamination were significantly correlated with the soil type, vegetation type, geological substrates, geomorphological features, and annual precipitation. The vegetation recovery of dominant desert communities in the study area was influenced by soil type, geomorphological feature, and TPH‐contaminated areas. Interestingly, the results showed that these desert communities can recover in areas contaminated by TPH at a higher rate than noncontaminated sites in the study area. Such a study can provide important inputs to the restoration and revegetation programs in arid landscapes.