Naphthenic acids are a group of polar organic carboxylic acids that are present in crude oil naturally. They are cycloaliphatic carboxylic acids which have 10 to 16 carbons, which gained importance since the early twentieth century because of corrosion in oil refineries. Moreover, they are the most important environmental pollutants caused by oil extraction from oil sand reserves. Heavy crude oils which have high concentration of naphthenic acids are usually considered as poor-quality oil and sold at a lower price. Often, the high concentration of naphthenic acids in crude oil reduces the life of the equipment which are used in the exploration and refining process because of corrosion. Hence, researchers are increasingly interested in the chemical properties of naphthenic acids and the acidic components of the crude oils. The most popular methods for the identification and analysis of naphthenic acids are liquid and gas chromatography (GC), liquid-liquid extraction, Fourier transform infrared spectroscopy (FTIR), and solid-phase extraction (SPE). Naphthenic acids are the most important environmental pollutants caused by oil extraction from oil sand reserves. Previous studies have revealed that naphthenic acids can be absorbed by fish, but their distribution in different tissues of fish has not been specified. Experimental samples showed the highest toxicity to fish, while there was less toxicity to invertebrates and algae. Moreover, naphthenates have various industrial utilizations; they are used in synthetic detergents, corrosion inhibitors, lubricants, fuel and oil additives, wood preservatives, insecticides, fungicides, pesticides, wetting agents, napalm thickening agents, and oil desiccants that are utilized in painting and treating wood surfaces.

In this research, successive electro-oxidation (EO) process was utilized to eliminate some of the primary organic contaminants in effluent wastewater, specifically phenol and chemical oxygen demand (COD). The performance of the electro-oxidation (EO) process was studied by using two graphite electrodes as anodes and three stainless steel electrodes as cathodes, which is a new strategy in this field. Taguchi method has been used to design experiments to approach the best experimental conditions for phenol and COD removal as significant responses. The best operating conditions that resulted in the maximum reduction of phenol and COD were current density (CD = 25 mA/cm2), pH = 4, support electrolyte (NaCl=2g/l), the distance between electrodes (Dist.=5mm), and time of 60 minutes. At these operating conditions, phenol and COD removal were 99.27% and 99.96%, respectively. This work provides important insights into a novel water and wastewater treatment method with a detailed analysis of the results.

Persistent pollution of surface waters by hydrocarbon compounds is one of the foremost threats to limited global freshwater resources. This study analyzed the abundance, diversity and degradative capacities of hydrocarbon-utilizing bacteria in chronically polluted Kono River in the Nigerian Niger Delta in order to establish the bacterial drivers of ecological regeneration of the river after an oil spill. The study further aimed to develop a specialized bacterial consortium for application in bioremediation interventions. Bacillus, Pseudomonas and Enterobacter spp. were predominant out of the 82 isolates obtained. Klebsiella pneumoniae and two species of Enterobacter cloacae were identified as the most efficient hydrocarbon utilizers. The isolates were also confirmed as biosurfactant producers and possessed the alkB1 and nahAc genes for degradation of aliphatics and aromatics. E. cloacae-K11, K. pneumoniae-K05, E. cloacae-K12 and their consortium were able to degrade the total petroleum hydrocarbons and polycyclic aromatic hydrocarbons in batch systems by 59.37% – 96.06% and 68.40% – 92.46% respectively. K. pneumoniae-K05 showed the greatest petroleum degradation capacity of the three isolates but hydrocarbon degradation was most efficient with the bacterial consortium. The results obtained showed no significant differences at p≤0.05 between the degradation capacities of K. pneumoniae-K05 and the consortium for PAHs but a significant difference (p≤0.05) was seen with TPH degradation. A viable hydrocarbon degrading bacterial consortium was developed at the end of the study and it was concluded that the polluted river water displayed inherent potential for effective natural attenuation.

Aerobic bioremediation of oil contaminated soil was investigated on laboratory-scale for purpose of pilot-plant installation. Mineral oil was analysed using IR spectroscopy. Sediment was qualitative analysed on GC/MS. Research also included microbiological analysis.

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.

The main objective of this study was to investigate the 2019 and 2022 oil spill events that occurred off the coast of the State of Ceará, Northeastern Brazil. To further assess these mysterious oil spills, we investigated whether the oils stranded on the beaches of Ceará in 2019 and 2022 had the same origin, whether their compositional differences were due to weathering processes, and whether the materials from both were natural or industrially processed. We collected oil samples in October 2019 and January 2022, soon after their appearance on the beaches. We applied a forensic environmental geochemistry approach using both one-dimensional and two-dimensional gas chromatography to assess chemical composition. The collected material had characteristics of crude oil and not refined oils. In addition, the 2022 oil samples collected over 130 km of the east coast of Ceará had a similar chemical profile and were thus considered to originate from the same source. However, these oils had distinct biomarker profiles compared to those of the 2019 oils, including resistant terpanes and triaromatic steranes, thus excluding the hypothesis that the oil that reached the coast of Ceará in January 2022 is related to the tragedy that occurred in 2019. From a geochemical perspective, the oil released in 2019 is more thermally mature than that released in 2022, with both having source rocks with distinct types of organic matter and depositional environments. As the coast of Ceará has vast ecological diversity and Marine Protected Areas, the possibility of occasional oil spills in the area causing severe environmental pollution should be investigated from multiple perspectives, including forensic environmental geochemistry.

Soil polycyclic aromatic hydrocarbons (PAHs) generated from industrial processes are highly spatially heterologous, with limited quantitative studies on their main influencing factors. The present study evaluated the soil PAHs in three types of industrial parks (a petrochemical industrial park, a brominated flame retardant manufacturing park, and an e-waste dismantling park) and their surroundings. The total concentrations of 16 PAHs in the parks were 340–2.43 × 10³, 26.2–2.63 × 10³, and 394–2.01 × 10⁴ ng/g, which were significantly higher than those in the surrounding areas by 1–2 orders of magnitude, respectively. The highest soil PAH contamination was observed in the e-waste dismantling park. Nap can be considered as characteristic pollutant in the petrochemical industrial park, while Phe in the flame retardant manufacturing park and e-waste dismantling park. Low molecular weight PAHs (2–3 rings) predominated in the petrochemical industrial park (73.0%) and the surrounding area of brominated flame retardant manufacturing park (80.3%). However, high molecular weight PAHs (4–6 rings) were enriched in the other sampling sites, indicating distinct sources and determinants of soil PAHs. Source apportionment results suggested that PAHs in the parks were mainly derived from the leakage of petroleum products in the petroleum manufacturing process and pyrolysis or combustion of fossil fuels. Contrarily, the PAHs in the surrounding areas could have been derived from the historical coal combustion and traffic emissions. Source emissions, wind direction, and local topography influenced the PAH spatial distributions.

Petroleum hydrocarbon pollution is a global problem. However, the effects of different petroleum pollution levels on soil microbial communities and ecological functions are still not clear. In this study, we analyzed the changes in microbial community structures and carbon and nitrogen transformation functions in oil-contaminated soils at different concentrations by chemical analysis, high-throughput sequencing techniques, cooccurrence networks, and KEGG database comparison functional gene annotation. The results showed that heavy petroleum concentrations (petroleum concentrations greater than 20,000 mg kg⁻¹) significantly decreased soil microbial diversity (p = 0.01), soil microbiome network complexity, species coexistence patterns, and prokaryotic carbon and nitrogen fixation genes. In medium petroleum contamination (petroleum concentrations of between 4000 mg kg⁻¹ and 20,000 mg kg⁻¹), microbial diversity (p > 0.05) and carbon and nitrogen transformation genes showed no evident change but promoted species coexistence patterns. Heavy petroleum contamination increased the Proteobacteria phylum abundance by 3.91%–57.01%, while medium petroleum contamination increased the Actinobacteria phylum abundance by 1.69%–0.26%. The results suggested that petroleum concentrations played a significant role in shifting soil microbial community structures, ecological functions, and species diversities.