Hydrocarbon-contaminated Sites Research Articles

Research on pollution identification and safety thresholds based on the olfactory effect on a halogenated hydrocarbon contaminated site

To effectively address odor control issues at sites contaminated with halogenated hydrocarbons, it is essential to establish an odor risk prediction system for evaluating potential risks that may impact future planning. This research focuses on a representative halogenated hydrocarbon-contaminated site, examining the spatial and temporal distribution characteristics of key pollutants in soil gas. By analyzing odor contribution rates, the study identifies significant odorants in soil gas, which enables the derivation of both probabilistic and deterministic safety thresholds for soil and groundwater based on olfactory effects. The findings indicate that 1,1-dichloroethylene, vinyl chloride, chloroform, and 1,1-dichloroethane are prevalent throughout the contaminated site, displaying elevated concentration levels and substantially influencing the overall contamination extent. These substances are highlighted as critical pollutants requiring attention. Correlation analysis (P < 0.05) reveals a strong relationship between the concentrations of vinyl chloride, 1,1-dichloroethane, and chloroform with groundwater depth and air temperature. Additionally, the analysis of odor activity values (OAV) identified 1,1-dichloroethene, 1,4-dichlorobenzene, chlorobenzene, chloroform, and vinyl chloride as key olfactory factors at the site. The corresponding probabilistic safety thresholds are 0.68, 1.65, 0.50, 7.87, and 3.72 mg kg−1 for soil, and 9.29, 3.46, and 1.09, 69.55, and 47.01 mg L−1 for groundwater, respectively. Among them, the odor risks of chlorobenzene and 1,1-dichloroethylene warrant more attention than soil contamination risks; regarding 1,4-dichlorobenzene, it is recommended to concurrently consider odor risks during human health risk assessment; as for vinyl chloride and chloroform, their odor risks can be largely eliminated based on human health-oriented pollution management.

High Arctic Seawater and Coastal Soil Microbiome Co-occurrence and Composition Structure and Their Potential Hydrocarbon Biodegradation

Abstract The accelerated decline in Arctic sea-ice cover and duration is enabling the opening of Arctic marine passages and improving access to natural resources. The increasing accessibility to navigation and resource exploration and production brings risks of accidental hydrocarbon releases into Arctic waters, posing a major threat to Arctic marine ecosystems where oil may persist for many years, especially in beach sediment. The composition and response of the microbial community to oil contamination on Arctic beaches remain poorly understood. To address this, we analyzed microbial community structure and identified hydrocarbon degradation genes among the Northwest Passage intertidal beach sediments and shoreline seawater from five high Arctic beaches. Our results from 16S/18S rRNA genes, long-read metagenomes and metagenome-assembled genomes reveal the composition and metabolic capabilities of the hydrocarbon microbial degrader community, as well as tight cross-habitat and cross-kingdom interactions dominated by lineages that are common and often dominant in the polar coastal habitat, but distinct from petroleum hydrocarbon-contaminated sites. In the polar beach sediment habitats, Granulosicoccus sp. and Cyclocasticus sp. were major potential hydrocarbon-degraders, and our metagenomes revealed a small proportion of microalgae and algal viruses possessing key hydrocarbon biodegradative genes. This research demonstrates that Arctic beach sediment and marine microbial communities possess the ability for hydrocarbon natural attenuation. The findings provide new insights into the viral and microalgal community possessing hydrocarbon degradation genes and might represent an important contribution to the removal of hydrocarbon under harsh environmental conditions in a pristine, cold, and oil-free environment that is threatened by oil spills.

A biodegradable chitosan-based polymer for sustained nutrient release to stimulate groundwater hydrocarbon-degrading microflora

Petroleum hydrocarbon-contaminated groundwater often has a low indigenous microorganism population and lacks the necessary nutrient substrates for biodegradation reaction, resulting in a weak natural remediation ability within the groundwater ecosystem. In this paper, we utilized the principle of petroleum hydrocarbon degradation by microorganisms to identify effective nutrients (NaH2PO4, K2HPO4, NH4NO3, CaCl2, MgSO4·7H2O, FeSO4·7H2O, and VB12) and optimize nutrient substrate allocation through a combination of actual surveys of petroleum hydrocarbon-contaminated sites and microcosm experiments. Building on this, combining biostimulation and controlled-release technology, we developed a biodegradable chitosan-based encapsulated targeted biostimulant (i.e., YZ-1) characterized by easy uptake, good stability, controllable slow-release migration, and longevity to stimulate indigenous microflora in groundwater to efficiently degrade petroleum hydrocarbon. Results showed that YZ-1 extended the active duration of nutrient components by 5–6 times, with a sustainable release time exceeding 2 months. Under YZ-1 stimulation, microorganisms grew rapidly, increasing the degradation rate of petroleum hydrocarbon (10 mg L−1) by indigenous microorganisms from 43.03% to 79.80% within 7 d. YZ-1 can easily adapt to varying concentrations of petroleum hydrocarbon-contaminated groundwater. Specifically, in the range of 2–20 mg L−1 of petroleum hydrocarbon, the indigenous microflora was able to degrade 71.73–80.54% of the petroleum hydrocarbon within a mere 7 d. YZ-1 injection facilitated the delivery of nutrient components into the underground environment, improved the conversion ability of inorganic electron donors/receptors in the indigenous microbial community system, and strengthened the co-metabolism mechanism among microorganisms, achieving the goal of efficient petroleum hydrocarbon degradation.

Structure and Assembly Mechanism of Archaeal Communities in Deep Soil Contaminated by Chlorinated Hydrocarbons

Chlorinated hydrocarbons are typical organic pollutants in contaminated sites, and microbial remediation technology has attracted more and more attention. To study the structural characteristics and assembly mechanism of the archaeal community in chlorinated hydrocarbon-contaminated soil, unsaturated-zone soil within 2~10 m was collected. Based on high-throughput sequencing technology, the archaeal community was analyzed, and the main drivers, environmental influencing factors, and assembly mechanisms were revealed. The results showed that chlorinated hydrocarbon pollution altered archaeal community structure. The archaeal community composition was significantly correlated with trichloroethylene (r = 0.49, p = 0.001), chloroform (r = 0.60, p = 0.001), pH (r = 0.27, p = 0.036), sulfate (r = 0.21, p = 0.032), and total carbon (r = 0.23, p = 0.041). Under pollution stress, the relative abundance of Thermoplasmatota increased to 25.61%. Deterministic processes increased in the heavily polluted soil, resulting in reduced species richness, while positive collaboration among surviving species increased to 100%. These results provide new insights into the organization of archaeal communities in chlorinated hydrocarbon-contaminated sites and provide a basis for remediation activities.

Depth and contaminant-shaped bacterial community structure and assembly at an aged chlorinated aliphatic hydrocarbon-contaminated site

Chlorinated aliphatic hydrocarbons (CAHs) are potentially toxic substances that have been detected in various contaminated environments. Biological elimination is the main technique of detoxifying CAHs in the contaminated sites, but the soil bacterial community at CAH-contaminated sites have been little investigated. Here, high-throughput sequencing analysis of soil samples from different depths (to 6 m depth) at an aged CAH-contaminated site has been conducted to investigate the community composition, function, and assembly of soil bacteria. The alpha diversity of the bacterial community significantly increased with increasing depth and bacterial community also became more convergent with increasing depth. Organohalide-respiring bacteria (OHRB) is considered keystone taxa to reduce the environmental stress of CAHs by reductive dechlorinate CAHs into nontoxic products, increases the alpha diversity of bacterial community and improves the stability of bacterial co-occurrence network. The high concentration of CAHs in deep soil and the stable anaerobic environment make deterministic processes dominate bacterial community assembly, while the topsoil is dominated by dispersal limitation. In general, CAHs at contaminated sites have a great impact on bacterial community, but the CAHs metabolic community acclimated in deep soil can reduce the environmental stress of CAHs, which provides foundation for the monitored natural attenuation technology in CAHs-contaminated sites.

Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites.

Kerosene is widely used in Ethiopia as a household fuel (for lighting and heating), as a solvent in paint and grease, and as a lubricant in glass cutting. It causes environmental pollution and escorts to loss of ecological functioning and health problems. Therefore, this research was designed to isolate, identify, and characterize indigenous kerosene-degrading bacteria that are effective in cleaning ecological units that have been contaminated by kerosene. Soil samples were collected from hydrocarbon-contaminated sites (flower farms, garages, and old-aged asphalt roads) and spread-plated on mineral salt medium (Bushnell Hass Mineral Salts Agar Medium: BHMS), which consists of kerosene as the only carbon source. Seven kerosene-degrading bacterial species were isolated, 2 from flower farms, 3 from garage areas, and 2 from asphalt areas. Three genera from hydrocarbon-contaminated sites were identified, including Pseudomonas, Bacillus, and Acinetobacter using biochemical characterization and the Biolog database. Growth studies in the presence of various concentrations of kerosene (1% and 3% v/v) showed that the bacterial isolates could metabolize kerosene as energy and biomass. Thereby, a gravimetric study was performed on bacterial strains that proliferated well on a BHMS medium with kerosene. Remarkably, bacterial isolates were able to degrade 5% kerosene from 57.2% to 91% in 15 days. Moreover, 2 of the most potent isolates, AUG2 and AUG1, resulted in 85% and 91% kerosene degradation, respectively, when allowed to grow on a medium containing kerosene. In addition, 16S rRNA gene analysis indicated that strain AAUG1 belonged to Bacillus tequilensis, whereas isolate AAUG showed the highest similarity to Bacillus subtilis. Therefore, these indigenous bacterial isolates have the potential to be applied for kerosene removal from hydrocarbon-contaminated sites and the development of remediation approaches.

Studies on the morphology, phylogeny, and bioremediation potential of Penicillium citrinum and Paecilomyces variotii (Eurotiales) from oil-contaminated areas.

Crude oil pollution is one of the most arduous issues to address, as it is hazardous to both public health and the environment. The discovery of novel biosurfactants-producing fungi and bacteria is in high demand due to their excellent properties and wide range of applications. The aim of this research is to isolate a powerful biosurfactant-producing fungus from the crude oil site near Barauni oil refinery in Bihar, India. Standard protocols were used to collect samples from the site. An integrative taxonomic approach was used, which included morphological, molecular, and phylogenetic analysis. The use of plating samples on Bushnell-Hass (BH) media aided in the isolation of a fungal strain from an enrichment culture. Two fungal strains isolated from contaminated soils, Penicillium citrinum and Paecilomyces variotti, showed potent oil degrading activity in a single culture. For preliminary biosurfactants screening, drop collapse assays, oil spreading, and emulsification activity tests were used. The results showed that the cultures performed well in the screening test and were further evaluated for degradation capacity. Different treatment periods (0, 3, 6, 9, 12, and 15days) were used to observe degradation in single cultures. A steady drop in pH, an alteration in optical density and an increase in carbon dioxide release showed the ability of fungal strain to degrade the crude oil in a single culture. Fungi mycelia provide a larger surface area for absorption and degradation of the pollutants in contaminated environment. They produce extracellular enzymes to degrade the oil, and at the same time absorb and utilise carbon, allowing them to remove toxic substances from the oil. Thus, they could be candidates for bioremediation of a hydrocarbon-contaminated site.

Investigating the succession process of native desert plants over hydrocarbon-contaminated soils using remote sensing techniques

Hydrocarbon-contaminated soils are considered as one of the major environmental issues that harm human well-being, particularly in arid regions of the world. Phytoremediation is a possible mitigation measure for this issue and has been suggested as it is cost-effective compared with other remediation technologies for soil clean-up, such as soil thermal treatment and soil washing. However, there are still gaps in the literature regarding the behavior of annual and perennial desert plants and their ability to survive in hydrocarbon-contaminated soils in arid ecosystems. Therefore, this study aims to develop an integrated approach using remote sensing techniques to understand the behavior of annual and perennial desert plants over different types of oil-contaminated soils (oil tarcrete, wet-oil lake, bare soil, and vegetation cover) in the Kuwait Desert and to explore the impact of climate and physical soil properties on the regrowth of native desert plants. The Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and ferrous iron (Fe2+) index (FI) were used to determine the changes in oil contamination and vegetation cover from 1992 to 2002, and 2013–2020. Subsequently, statistical tests were performed to determine the influence of climatic and soil physical characteristics on changes in hydrocarbon contamination and desert plant behavior. The results showed that hydrocarbon contamination was high at the study sites in the first six years (1992–1997) after contamination, and then decreased in the following years. However, vegetation cover was low in the first six years but significantly increased after 1998, reaching >65%. It was also found that annual plants had the highest distribution rate compared to perennial plants, which mainly depended on the soil type. We concluded that certain annual and perennial plants could successfully grow over tarcrete-contaminated sites, making these sites more suitable for the restoration of native desert plants than hydrocarbon-contaminated sites. We also observed that the succession process of vegetation growth over hydrocarbon-contaminated soils could be associated with vegetation growth on a clean sediment layer covering the oil layer. Additionally, we observed that the remobilization of aeolian sediment over many contaminated sites in Kuwait resulted in the accumulation of organic matter, plant seeds, and dust particles that create layers of nutrient-rich soil for the initial growth of plants.

Effective bioremediation of petroleum-contaminated saline soil using halotolerant Bacillus strains isolated from the Persian Gulf.

A consortium isolated from the Persian Gulf is evaluated for its ability to bioremediate petroleum-contaminated soils. The soil sample was collected from oil fields of South Western Iran. The crude oil concentrations were set to 1000-10,000 mg/kg, and the sodium chlorideconcentration was set to 0.5%, 1%, 1.5%, 2%, and 2.5%. Operational parameters including volume (2-20 ml) and soil moisture (25%, 50%, and 100%) were studied consecutively according to one factor at the time of experimental design. A total number of eight different isolates capable of degrading crude oil were isolated from hydrocarbon-contaminated sites (KL1-KL8). The removal efficiency of Total petroleom hydrocarbons (TPH) with an initial concentration of 1000 mg/kg for numbers of bacterial cells per gram soil of 2, 10, and 20 CFU/g was 20.9%, 45%, and 60%, respectively. The removal efficiency of TPHs (initial concentration of 1000 mg/kg) at the end of fifth week for salinity amounts of 0.5%, 1%, 1.5%, 2%, and 2.5% was 10.87%, 22.4%, 25.7%, 68.6%, and 60.5%, respectively. The TPHs biodegradation efficiencies at different soil/water ratios of 25%, 50%, and 100% (slurry) were 12%, 28.7%, and 60.8%, respectively. In sunflowers, there was no statistically significant difference in seed germination for different levels of soil pollution (p > 0.05). The results of the current work suggest that this process is a viable and efficient method for remediating contaminated sites. To enhance the removal results in real soil, a scale-up study should also be conducted.

Patterns of groundwater bacterial communities along the petroleum hydrocarbon gradient

Groundwater contamination by petroleum hydrocarbons has become a worldwide environmental problem. Despite that microorganisms played an important role in biogeochemical processes such as hydrocarbon degradation, comprehensive understanding of the structure, function, and interactions of groundwater bacterial communities in petroleum hydrocarbon-contaminated sites is still lacking. Here we investigated the groundwater bacterial communities along a total petroleum hydrocarbon gradient (TPH: 0.01–2.09 mg/L) at an abandoned chemical factory site by sequencing microbial 16 S rRNA gene amplicons. Results showed that hydrocarbon contamination in groundwater reduced the bacterial diversity, and favored the growth of some species, such as members of the β-, γ-Proteobacteria and Planctomycetes. TPH exerted profound selection pressure on the bacterial community, as the variation of community structure along the TPH gradient were significantly correlated with the petroleum hydrocarbon tolerance of the community (r = 0.362; p < 0.001). Other geochemical variables of the groundwater, including pH, sampling depth, oxidation-reduction potential, temperature, and dissolved oxygen, also influenced the community structure. Variations in bacterial community structure thus altered the functional potential, with significantly higher alkane (alkB and alkH) and PAH (nahF and phdK) degradation gene abundances in the relatively high contaminated sampling wells. By conducting the ecological network analysis, we identified a potentially important ecological module relating to petroleum hydrocarbon degradation, which is mainly composed of members of Proteobacteria. This suggested the potential metabolic cross-feeding relationship of Proteobacteria in utilizing petroleum hydrocarbon. These findings illustrate an overall picture of bacterial communities involved in a petroleum hydrocarbon contamination site and provided useful information for groundwater restoration and environmental management.

The state of the intestinal bacterial community in mollusks for assessing habitat pollution in the gulf of Finland (Baltic Sea)

In this study, we investigated the abundance and diversity of bacteria in the digestive tract of the bivalve mollusks Unio pictorum after 30-day exposure in experimental cages and field-collected gastropod mollusk Radix balthica in the eastern Gulf of Finland, Baltic Sea. Contamination of water and sediments with petroleum hydrocarbons had a significant impact on the intestinal bacterial community of mollusks stimulating the growth of hydrocarbon-oxidizing bacteria. The abundance of the intestinal hydrocarbon-oxidizing bacteria correlated with the concentration of the total hydrocarbons in the water of the coastal sites in the Gulf, where the mollusks were exposed. Metagenomic analysis revealed significant differences in the intestinal microbial community composition between polluted and unpolluted sites. The increased abundance of members of the phylum Gammaproteobacteria, including species of Aeromonas, Acinetobacter, Arenimonas, Pseudomonas, Rheinheimera, and Shewanella, and Bacteroidetes (Flavobacterium and Pedobacter) in the intestinal tracts of mollusks Unio pictorum were found at hydrocarbon-contaminated site: therefore, these bacteria are key players in the adaptation of intestinal community to this kind of pollution and hydrocarbon degradation. Our study suggests that hydrocarbon-oxidizing bacteria have the potential as a sensitive bioindicator for the further monitoring and ecological assessment of marine ecosystems.

Comparison of the efficiency and microbial mechanisms of chemical- and bio-surfactants in remediation of petroleum hydrocarbon

Surfactant-enhanced remediation (SER) is one of the most effective methods for petroleum hydrocarbon-contaminated sites compared to single physical and chemical methods. However, biosurfactants are not as commonly used as chemical surfactants, and the actual remediation effects and related mechanisms remain undefined. Therefore, to comprehensively compare the remediation effects and biological mechanisms of biosurfactants and chemical surfactants, soil column leaching experiments including two biosurfactants (rhamnolipids and lipopeptide) and three commercially used chemical surfactants (Tween 80, Triton X-100, and Berol 226SA) were conducted. After seven days of leaching, rhamnolipids exhibited the highest petroleum hydrocarbon removal rate of 61.01%, which was superior to that of chemical surfactants (11.73–18.75%) in n-alkanes C10–C30. Meanwhile, rhamnolipids exhibited a great degradation advantage of n-alkanes C13–C28, which was 1.22–30.55 times that of chemical surfactants. Compared to chemical surfactants, biosurfactants significantly upregulated the soil's biological functions, including soil conductivity (80.90–155.56%), and soil enzyme activities of lipase (90.31–497.10%), dehydrogenase (325.00–655.56%), core enzyme activities of petroleum hydrocarbon degradation, and quorum sensing between species. Biosurfactants significantly changed the composition of Pseudomonas, Citrobacter, Acidobacteriota, and Enterobacter at the genus level. Meanwhile, chemical surfactants had less influence on the bacterial community and interactions between species. Moreover, the biosurfactants enhanced the microbial interactions and centrality of petroleum hydrocarbon degraders in the community based on the network. Overall, this work provides a systematic comparison and understanding of the chemical- and bio-surfactants used in bioremediation. In the future, we intend to apply biosurfactants to practical petroleum hydrocarbon-contaminated fields to observe realistic remediation effects and compare their functional mechanisms.

Microwave-induced steam distillation (MISD) remediation in petroleum hydrocarbon-contaminated sites: From process improvement to pilot application

The process improvement, a pilot remediation test and the decontamination mechanism of microwave-induced steam distillation (MISD) for petroleum hydrocarbons (PHs) removal were conducted. Processes of multistage steam distillation and carbon reinforcement were compared to determine the best remediation process. Pilot project was then carried out to explore the applicability of MISD in site-scale remediation. The remediation efficiency, procedures and influencing factors of site-scale MISD project were studied by monitoring variations of soil moisture, temperature and PHs concentrations. Furthermore, the decontamination mechanisms of PHs were clarified based on kinetic analysis. The results showed that the multistage steam distillation could improve 10%∼15% remediation efficiency, and the carbon reinforcement could shorten remediation duration of each steam distillation stage by 50%. Pilot MISD project adopted multistage steam distillation process and went through four (initial, rapid heating-up, gentle heating-up and quasi-equilibrium) remediation stages (overall temperature ≤100 °C). The final PHs removal rate was about 60%, which would get better with greater proportion of low boiling points components and stronger vapor extraction. Kinetic studies showed that PHs was removed by steam stripping and limited by intraparticle diffusion in the “steam distillation zone”, while local high temperature (＞100 °C) greatly improved PHs volatilization and provided activation energy for PHs desorbed and degraded in the “selective heating zone".

Contamination presence and dynamics at a polluted site: Spatial analysis of integrated data and joint conceptual modeling approach

Contaminated sites are complex systems posing challenges for their characterization as both contaminant distribution and hydrogeological properties vary markedly at the metric scale, yet may extend over broad areas, with serious issues of spatial under-sampling in the space. Characterization with sufficient spatial resolution is thus, one of the main concerns and still open areas of research. To this end, the joint use of direct and indirect (i.e., geophysical) investigation methods is a very promising approach. This paper presents a case study aspiring to demonstrate the benefit of a multidisciplinary approach in the characterization of a hydrocarbon-contaminated site. Detailed multi-source data, collected via stratigraphic boreholes, laser-induced fluorescence (LIF) surveys, electrical resistivity tomography (ERT) prospecting, groundwater hydrochemical monitoring, and gas chromatography–mass spectrometry (GC–MS) analyses were compiled into an interactive big-data package for modeling activities. The final product is a comprehensive conceptual hydro-geophysical model overlapping multi-modality data and capturing hydrogeological and geophysical structures, as well as contamination distribution in space and dynamics in time. The convergence of knowledge in the joint model verifies the possibility of discriminating geophysical findings based on lithological features and contamination effects, unmasking the real characteristics of the pollutant, the contamination mechanisms, and the residual phase hydrocarbon sequestration linked to the hydrogeological dynamics and adopted remediation actions. The emerging conceptual site model (CSM), emphasizing the necessity of a large amount of multi-source data for its reliable, high-resolution reconstruction, appears as the necessary tool for the design of remedial actions, as well as for the monitoring of remediation performance.

Optimization of conditions for a surfactant-producing strain and application to petroleum hydrocarbon-contaminated soil bioremediation

Petroleum hydrocarbon-contaminated sites have been mainly remediated through the surfactant-enhanced soil leaching method. However, the commonly used chemical surfactants have poor biocompatibility and are prone to form residues in fields. Therefore, the purpose of this research is to establish an effective system of biosurfactant remediation in the field and provide instructions for common bioremediation challenges. First, wild-type Bacillus amyloliquefaciens A3, which produced lipopeptide biosurfactant, was used to improve the production of biosurfactant by atmosphere and room temperature plasma (ARTP) mutagenesis. Second, the mutant 1–24 was selected from a total of 174 mutants due to the outstanding yield. Subsequently, 1–24 was applied in the soil column leaching experiments and removed 45.44% of petroleum hydrocarbons by changing the relevant enzyme activities. Biosurfactant addition and 1–24 inoculation effectively activated a portion of the petroleum hydrocarbons in the soil columns, and 1–24 presented potential as a desired candidate for bioremediation. This is the first report of using ARTP mutagenesis to improve the production of biosurfactants. Simultaneously, we first propose a theoretical system in which the yield of biosurfactant was increased using ARTP mutagenesis for strains and applied the mutants in situ soil bioremediation. This research indicated that the theoretical system was useful in soil columns to simulate field remediation conditions, providing practical references for the bioremediation of contaminated soil.

Characterization and Application of Biopolymer Producing Bacteria for Enhanced Oil Recovery

The objective of this research is to isolate and identify hydrocarbon-degrading bacteria for biopolymer synthesis and application in the augmentation of Nigerian heavy crude oil recovery. MEOR refers to the process of injecting either indigenous or non-indigenous microbes into hydrocarbon reserves. Injecting microorganisms with nutritional broth facilitate the formation of essential metabolites such as biosurfactants, biopolymers, and gases, resulting in decreased interfacial tension, viscosity modification, and mobility control. It is environmentally friendly, less expensive to implement, and requires minimal or no changes to the existing infrastructure. A soil sample from a hydrocarbon-contaminated site in Ogoniland was collected and sent to a laboratory for physicochemical and microbiological investigation. Bacillus sp, Pseudomonas sp, and Klebsiella sp were biochemically identified after screening three isolates for biopolymer production using Sudan black solution. To assess the ideal growth and biopolymer synthesis capability under reservoir conditions, a variety of pH, temperature, salinity, carbon, and nitrogen nutrition sources were applied to selected microorganisms. Peptone is the optimal nitrogen source for Bacillus sp, glucose is the optimal carbon source for Bacillus sp, and glycerol is the optimal carbon source for Pseudomonas sp and Klebsiella sp, as indicated by the results. In addition, the following are the ideal parameter ranges for the three microorganisms: pH 7–8, a temperature range between 25 and 350 degrees Celsius, and a salinity range between 0.5 and 5% are all desirable conditions for a body of water. After inoculation with microorganisms and the optimum nutrient source, an additional recovery range of 18.33% to 29.09% of the pore capacity was achieved. The post-recovery analysis uncovered a remarkable transformation of heavy crude to light hydrocarbon components by an average of 20.33 percent with glucose and 97.27 percent with peptone.

Isolation and Characterization of Diesel-Degrading Bacteria from Hydrocarbon-Contaminated Sites, Flower Farms, and Soda Lakes.

Hydrocarbon-derived pollutants are becoming one of the most concerning ecological issues. Thus, there is a need to investigate and develop innovative, low-cost, eco-friendly, and fast techniques to reduce and/or eliminate pollutants using biological agents. The study was conducted to isolate, characterize, and identify potential diesel-degrading bacteria. Samples were collected from flower farms, lakeshores, old aged garages, asphalt, and bitumen soils and spread on selective medium (Bushnell Haas mineral salt agar) containing diesel as the growth substrate. The isolates were characterized based on their growth patterns using optical density measurement, biochemical tests, and gravimetric analysis and identified using the Biolog database and 16S rRNA gene sequencing techniques. Subsequently, six diesel degraders were identified and belong to Pseudomonas, Providencia, Roseomonas, Stenotrophomonas, Achromobacter, and Bacillus. Among these, based on gravimetric analysis, the three potent isolates AAUW23, AAUG11, and AAUG36 achieved 84%, 83.4%, and 83% diesel degradation efficiency, respectively, in 15 days. Consequently, the partial 16S rRNA gene sequences revealed that the two most potent bacterial strains (AAUW23 and AAUG11) were Pseudomonas aeruginosa, while AAUG36 was Bacillus subtilis. This study demonstrated that bacterial species isolated from hydrocarbon-contaminated and/or uncontaminated environments could be optimized to be used as potential bioremediation agents for diesel removal.

Upotreba fluorescencije indukovane laserskim zračenjem (LIF) kao metode u Sjedinjenim Američkim Državama

Spatial characterization of the contamination is a fundamental component of any remediation approach. Compared to conventional investigation methods, the laser-induced fluorescence (LIF) is a faster screening tool and provides the detection of hydrocarbon contamination in real-time. This investigation was conducted at a hydrocarbon-contaminated site in Pennsylvania, US. The presence of light nonaqueous-phase liquids (LNAPL) was detected in 6 of 17 LIF borings, with the reference emitter responses ranging between 45% and 225%. The depth of the response was highly accurate and valuable and provided insight into the spatial distribution of contamination. The results indicated that no substantial amount of LNAPL existed along the LIF borings profile, thus excluding this area as a preferential LNAPL migration pathway. The obtained results contributed to the characterization and remediation of this industrial site.

Hydrocarbon-Contaminated Sites: Is There Something More Than Exophiala xenobiotica? New Insights into Black Fungal Diversity Using the Long Cold Incubation Method.

Human-made hydrocarbon-rich environments are important reservoirs of microorganisms with specific degrading abilities and pathogenic potential. In particular, black fungi are of great interest, but their presence in the environment is frequently underestimated because they are difficult to isolate. In the frame of a biodiversity study from fuel-contaminated sites involving 30 diesel car tanks and 112 fuel pump dispensers (52 diesel and 60 gasoline, respectively), a total of 181 black fungal strains were isolated. The long cold incubation (LCI) of water-suspended samples, followed by plating on Dichloran Rose Bengal Chloramphenicol Agar (DRBC), gave isolation yields up to six times (6.6) higher than those of direct plating on DRBC, and those of enrichment with a phenolic mix. The sequencing of ITS and LSU-rDNA confirmed the dominance of potentially pathogenic fungi from the family Herpotrichiellaceae and Exophiala xenobiotica. Moreover, other opportunistic species were found, including E. opportunistica, E. oligosperma, E. phaeomuriformis, and Rhinocladiella similis. The recurrent presence of E. crusticola, Knufia epidermidis, Aureobasidium melanogenum, Cladosporium spp., and Scolecobasidium spp. was also recorded. Interestingly, 12% of total isolates, corresponding to 50% of taxa found (16/32), represent new species. All the novel taxa in this study were isolated by LCI. These findings suggest that black fungal diversity in hydrocarbon-rich niches remains largely unexplored and that LCI can be an efficient tool for further investigations.

Catabolic enzyme activity and kinetics of pyrene degradation by novel bacterial strains isolated from contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) with high molecular weight are difficult to degrade owing to their chemical structure and stability. This study reports degradation of pyrene by two potent Gram-positive bacterial strains isolated from petroleum-contaminated soil from Bijwasan supply location of Bharat Petroleum Corporation Limited (BPCL), India. The bacteria were identified as Kocuria flava and Rhodococcus pyridinivorans based on 16S rRNA gene sequencing. The degradation of pyrene, enzyme activity of Catechol 2,3-dioxygenase (C23O), dehydrogenase, and peroxidase, and the rate kinetics of degradation were investigated using the isolated bacteria. K. flava and R. pyridinivorans could degrade pyrene with an efficiency of 53.8% and 56.2%, within 15 days of incubation period under laboratory conditions. The consortium revealed 56.4% degradation of pyrene indicating that there is no significant synergistic/inhibitive effect. The activity (maximum on 9th day of incubation) of peroxidase enzyme (9.4 × 10 −4 and 16.9 × 10 −4 μ M/ml/min) was followed by dehydrogenase (2.6 × 10 −4 and 2.3 × 10 −4 μ M/ml/min) and C23O (2.2 × 10 −4 and 2.8 × 10 −4 μ M/ml/min) for K. flava and R. pyridinivorans , respectively, suggesting their involvement in ring-cleavage, diol-formation, and subsequent oxidation of the intermediates. Analysis of rate kinetics exhibited degradation of pyrene to be the first order reaction indicating that an increase in initial concentration of pyrene will not compromise with the ability of studied bacteria towards degradation. Analysis of initial and final concentration of treated media over HPLC confirmed significant pyrene degradation within 15 days. The study concludes that K. flava and R. pyridinivorans can play an active role in remediation of hydrocarbon-contaminated sites. • Degradation of pyrene by K. flava and R. pyridinivorans reported for first time. • C23O enzyme regulates ring cleavage and peroxidase oxidises pyrene-intermediates. • No inhibitory effect of K. flava and R. pyridinivorans over each other.