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In recent years, significant efforts have been made to accelerate the economic development of the Arctic zone, leading to intense environmental pollution of this region, accompanied by the significant impact of accumulated environmental damage in the region. The solution to these problems is difficult due to the remoteness of these areas and severe climatic conditions. Therefore, it is important to evaluate the potential for restoration of arctic soils. For this purpose, various indicators are used, including biological ones. In the analyzed arctic soil samples, high concentrations of petroleum hydrocarbons (up to 47,000 mg/kg) and chloride-ions (0.10–0.14 wt %) were established. Microbioassay demonstrated a presence of hydrocarbon-oxidizing microorganisms: Penicillium, Azotobacter chroococcum, Bacillus subtilis, Pseudomonas oleovorans. A low enzymatic activity and specific Arctic climate point out a low self-restoration ability of the soil, demonstrated the need for its remediation. The microbioassay with microbial strains identification and soil remediation methods suitable for the Arctic zone were recommended.

Oil-contaminated soil is a major societal problem for humans and the environment. In this study, the pyrolysis method was applied to oil-contaminated soil used as a landfill and gas station site in Korea. The removal efficiency of the main components of oil-contaminated soils, such as total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAHs), unresolved complex mixture (UCM), and alkylated PAHs (Alk-PAHs) were measured, and the effect of temperature, treatment time, and moisture content on pyrolysis efficiency was studied. In order to evaluate the risk of soil from which pollutants were removed through pyrolysis, integrated ecotoxicity was evaluated using Daphnia magna and Allivibrio fischeri. The chemical and biological measurements in this study include contaminants of emerging concerns (CECs). Results showed that the pyrolysis was more efficient with higher treatment temperatures, moisture content, and treatment times. In addition, toxicity was reduced by 99% after pyrolysis, and the degree of toxicity was evaluated more sensitively in Allivibrio fischeri than in Daphnia magna. This study shows that weathered oil-contaminated soil can be effectively treated in a relatively short time through pyrolysis, as well as provides information on efficient conditions and the assessment of ecotoxicity.

Purpose: This study aimed to investigate the rapid restoration of indigenous hydrocarbon degraders after chemical oxidation, in order to enhance the subsequent biodegradation of crude oil in soils. Materials and methods: The Fe-SOM (2231 mg kg−1) and H2O2 were added into the oil-contaminated soil (total petroleum hydrocarbon (TPH): 16064 mg kg−1) for chemical oxidation. Then, the all and partial alkane re-biodegradation reagents were added for re-biodegradation experiments. Calculated and analyzed C-source (DOC and TPH) and N-source ( NH 4 + − N , NO 3 − − N , NO 2 − − N ) consumption and the population of hydrocarbon degraders in each period. Results and discussion: After chemical oxidation, the total biodegradation of all alkanes (re-biodegradation degree: 100%) with reagent for all alkane re-biodegradation in the late stage was higher than that in the early stage. Further study found that DOC was the main C-source and NH 4 + − N was the main N-source in the early stage, while TPH and nitrate were the main C&N-sources in the late stage of re-biodegradation. In other words, the C&N-sources changed over to TPH and nitrate in the late stage. After re-biodegradation stage, increasing biodegradation (from 644 mg kg−1 in the 1st stage to 842 mg kg−1 in the 3rd stage) was observed. Conclusions: The results showed that re-biodegradation of all alkanes could recover growth of indigenous hydrocarbon degraders and continuously increase biodegradation of all alkanes after chemical oxidation. The C&N-sources changed from DOC and NH 4 + − N to all alkanes and NO 3 − − N during re-biodegradation stage was the key factor. [ABSTRACT FROM AUTHOR]

Four hundred fifty four pyrosequencing was used to analyze the microbial community and diversity of oily farmland soil from Fushun, Liaoning Province, China. The results showed that a total of 114 Phyla, 262 Classes, 430 Orders, 685 Families, 869 Genera, and 294 Species were detected and summarized in the soil microbe. The petroleum hydrocarbons significantly changed the structure and diversity of soil microbial communities. Proteobacteria, Bacteroidetes, Actinobacteria, Acidobacteria, Gemmatimonadetes, Nitrospirae, Firmicutes, Verrucomicrobia, Elusimicrobia became the dominant flora in oil-contaminated areas. And the changes in the main bacterial flora in the soil were highly correlated with soil TPH (total petroleum hydrocarbon), pH and SOM (soil organic matter). The prediction of community metabolism function exhibited that 8 KEGG pathways were significantly enriched in petroleum contaminated soil, and the abundance of Proteobacteria, Moraxellaceae, Enterobacteriales and Sphingobacteriales significantly decreased under the stress of oil pollution. This research provided a theoretical and technical basis for the development and application of functional strains in the future. [ABSTRACT FROM AUTHOR]

Field experiments were conducted in 2016 and repeated in 2017 to evaluate the effectiveness of Oil Palm Bunch Ash (OPBA) and Dried Poultry manure (DPM) as organic supplement, applied singly and in combination on growth properties and heavy metal uptake of cassava cultivars grown in crude-oil contaminated soil of the Niger Delta Region, Nigeria. There were four different organic amendments viz: DPM, OPBA, OPBA +DPM and control using TMS 30572, NR8082 and local variety as test crops. Results were elaborated statistically with the use of three-by-four factor variance analysis with ANOVA. Effect of various application of amendment on morphometric parameters of cultivars revealed in 2017 that at 36 weeks after sprouting (WAS), DPM and OPBA +DPM significantly (P≤ 0.05) enhanced plant heights of TMS 3572 and LV but had no influence on number of nodes, stem girth and leaf area. However, the interactions resulted in significant (P≤ 0.05) uptake and concentration of the heavy metals Fe, Cu, and Pb in leaves and Fe in roots of TMS30572 and NR8082, indicating efficient metal removal by these varieties. Results of amendment also revealed remarkable increment in bacterial and fungal (from 104 to 106 and 103 to 104) populations respectively, correlating with reduction in soil total petroleum hydrocarbon (TPH) from 156.45 mg/kg to 146.73 mg/Kg. This is observed to diminish oil toxicity and improve soil status. The response of these cassava varieties to crude oil contamination appears to be optimistic. Consequently crop farmers are adviced against planting cassava and other arable crop at crude oil impacted soil for the risk of uptake of heavy metal in crop tissues. [ABSTRACT FROM AUTHOR]

In recent years, significant efforts have been made to accelerate the economic development of the Arctic zone, leading to intense environmental pollution of this region, accompanied by the significant impact of accumulated environmental damage in the region. The solution to these problems is difficult due to the remoteness of these areas and severe climatic conditions. Therefore, it is important to evaluate the potential for restoration of arctic soils. For this purpose, various indicators are used, including biological ones. In the analyzed arctic soil samples, high concentrations of petroleum hydrocarbons (up to 47,000 mg/kg) and chloride-ions (0.10-0.14 wt %) were established. Microbioassay demonstrated a presence of hydrocarbon-oxidizing microorganisms: Penicillium, Azotobacter chroococcum, Bacillus subtilis, Pseudomonas oleovorans. A low enzymatic activity and specific Arctic climate point out a low self-restoration ability of the soil, demonstrated the need for its remediation. The microbioassay with microbial strains identification and soil remediation methods suitable for the Arctic zone were recommended. [ABSTRACT FROM AUTHOR]

Petroleum hydrocarbons as pervasive pollutants pose a significant threat to soil ecology and human health. Surfactant washing as an established technique can effectively remediate soils contaminated by hydrocarbons. Biosurfactants, which combine the properties of surfactants and environmental compatibility, have attracted increasing interest. However, due to the high production cost of biosurfactants, their practical application is restricted. This study addressed these limitations by selecting two biosurfactants, β-cyclodextrin (C1) and sodium carboxymethyl cellulose (C2), and developed a promising cleaning agent formula through compounding and the addition of suitable additives. When the volume ratio of C1 to C2 was 8:2 and an 8 g/L mixture of sodium humate and sodium carbonate electrolyte was added, the surfactant system's surface tension reached a minimum, yielding optimal oil removal. The formation and synergistic behaviour of mixed micelles of surfactants were explained using ideal solution theory and the Rubingh model. By optimising the oil washing process parameters - normal temperature of 25 °C, pH 11, washing time of 2 h, solid-liquid ratio of 1:5, and oscillation frequency of 200 r/min - the oil removal rate achieved 76%. This cleaning agent, characterised by low production cost, straightforward application, environmental compatibility, and rapid, significant cleaning effect, shows potential for field-scale purification of petroleum-contaminated soil.

Oil pollution is a common type of soil organic pollution that is harmful to the ecosystem. Bioremediation, particularly microbe-assisted phytoremediation of oil-contaminated soil, has become a research hotspot in recent years. In order to explore more appropriate bioremediation strategies for soil oil contamination and the mechanism of remediation, we compared the remediation effects of three plants when applied in combination with a microbial agent and biochar. The combined remediation approach of Tagetes erecta , microbial agent, and biochar exhibited the best plant growth and the highest total petroleum hydrocarbons degradation efficiency (76.60%). In addition, all of the remediation methods provided varying degrees of restoration of carbon and nitrogen contents of soils. High-throughput sequencing found that microbial community diversity and richness were enhanced in most restored soils. Some soil microorganisms associated with oil degradation and plant growth promotion such as Cavicella , C1_B045 , Sphingomonas , MND1 , Bacillus and Ramlibacter were identified in this study, among which Bacillus was the major component in the microbial agent. Bacillus was positively correlated with all soil remediation indicators tested and was substantially enriched in the rhizosphere of T. erecta . Functional gene prediction of the soil bacterial community based on the KEGG database revealed that pathways of carbohydrate metabolism and amino acid metabolism were up-regulated during remediation of oil-contaminated soils. This study provides a potential method for efficient remediation of oil-contaminated soils and thoroughly examines the biochar-bacteria-plant combined remediation mechanisms of oil-contaminated soil, as well as the combined effects from the perspective of soil bacterial communities., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Fang, Zhang, Zheng, Wang, Wang, Lv and Shi.)

Oil-contaminated soils from a former landfill and gas station site in Korea were treated by thermal desorption. The removal efficiencies of the different oil components such as total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAHs), unresolved complex mixtures (UCM), and alkylated PAHs (Alk-PAHs) by thermal desorption were determined. The effects of temperatures (200, 400, and 600 °C) and treatment times (15, 30, 45, and 60 min) on the thermal desorption efficiency were studied. The treatment efficiency increased with increasing temperature from 200 to 400 °C and with increasing treatment time. Almost complete removals of TPH, UCM, PAHs, and Alk-PAHs were observed after 15 min at 400 °C. The treatment temperatures of 400 and 600 °C did not show a significant difference (p-value > 0.05). Overall, this study shows that the different components of oil in the oil-contaminated soils can be treated effectively in a relatively short time by thermal desorption, and such high removal efficiency in a relatively short time for the oil-contaminated soils can be of advantage for the treatment of highly contaminated or weathered soils where biological treatment efficiency is low. [ABSTRACT FROM AUTHOR]

Microbial sources are regularly used as reliable biocatalysts sources which are often used in the process and production industry. Demands for such organisms with greater capacity of intended enzyme production are on the rise. Lipase is important enzyme used in the biotechnological process of hydrolysis of fats in almost all the relevant industries We have utilized the local oil-contaminated soil resources to search for efficacious bacterial strains that have excellent lipase activity. We were successful in identifying two such bacterial sources, namely, Bacillus subtilis strain RCPS3 and Bacillus fumarioli strain RCPS4, responsible for lipase production from oil effluent contaminated soil of Telangana. This is the first report of these two strains from this part of India that are involved in lipase production. The strains were isolated, optimized, and purified using standard microbiology protocols and were characterized at the molecular level using the biomarker 16s ribosomal RNA genes of the strains. The identified and isolated bacterial strains were confirmed as Bacillus subtilis strain RCPS3, and Bacillus fumarioli strain RCPS4 through molecular and computational characterization. [ABSTRACT FROM AUTHOR]

Oil and oil products adversely affect both the biodiversity of the microorganisms and the soil function. In oil-contaminated soils, unique bacterial communities develop that are adapted to pollution. In this work, the bacterial structure and diversity of the microbial community have been studied in samples of oil-contaminated soils in Kazakhstan deposits using the Illumina MiSeq sequencer. The results of the study showed that the representatives of the following bacterial phyla dominated in the selected soil samples: Proteobacteria, prevailing in oil-contaminated soils (up to 48%), Actinobacteria (up to 29.33%), Firmicutes (up to 25.74%), Bacteroidetes (up to 33.28 %). The representatives of Planctomycetes, Verrucomicrobia, Chloroflexi (0.76% -4.62%) phyla were found in smaller amounts. All the uncontaminated soils were dominated by Micrococcaceae, Flexibacteraceae, Sphingomonadaceae, Planococcaceae, Flavobacteriaceae families, contaminated ones - by Halomonadaceae, Flavobacteriaceae, Alteromonadaceae, Dietziaceae, Pseudomonadaceae, Bacillaceae, Xanthomonadaceae, Anaerolinaceae, Mycobacteriaceae and Peptococcaceae families. At the genus level, samples of uncontaminated and contaminated soils also demonstrated significant diversity. The dominant bacterial genera in the samples of the uncontaminated soil were Hymenobacter, Arthrobacter, Gillisia. In contaminated soils of three deposits the microorganisms of the Halomonas, Marinobacter, Pseudomonas (mostly in 2KO soil sample), Bellilinea and Mycobacterium (mostly Md sample) genera were spread more widely; and a very large population of the microorganisms of the Halomonas genus was found in the contaminated soil sample from the Atyrau region. A comparison of the taxonomic structure of microbial communities of oil-contaminated soils indicates that the composition of the microbial population changes depending on the degree of oil pollution. Samples of uncontaminated background soils were characterized by higher bacterial diversity than samples of contaminated soils. The microorganisms belonging to the dominant phyla were mostly associated with the decomposition of oil hydrocarbons. The characterization of the bacterial communities living in the contaminated soils and the assessment of their ability to decompose oil can potentially be a guide for bioremediation of contaminated soils. [ABSTRACT FROM AUTHOR]

Potential reuse of oil-contaminated soils guidance policies are demonstrating ways to reuse these materials in engineering applications. However, the engineering properties of these materials are highly altered after contamination. Alternatively, chemical stabilization treatments can improve oil-contaminated soil properties for its reuse in geotechnical applications. This study investigates the effect of a diesel contamination on a coarse-grained soil and assesses the viability of a lime treatment. Laboratory tests included pH, Atterberg limits, compaction, unconfined compression strength (UCS), California Bearing Ratio (CBR) and tensile strength, RX-diffraction and scanning electron micrographs before and after lime treatment. Tests were performed on natural soil, diesel-contaminated soils (2, 4, 8, 12, and 16% of diesel) and lime treated diesel-contaminated soils (2, 4, 6 and 8% of lime). Diesel drastically changed soil plasticity and strength properties. Lime stabilization of diesel-contaminated soils was efficient to recapture soil natural properties with low lime contents. The influence of oil and lime in soil mechanical properties and mineralogical characteristics was evidenced in this study. The presence of oil drastically altered soil mechanical properties. Crystallization of calcite was present in both natural and oil-contaminated soils treated with lime, increasing particles flocculation. The presence of oil favored dolomite formation. Lime was significate in enhancing oil-contaminated soil mechanical properties, such as UCS, indirect tensile strength and CBR, mainly due to carbonation reactions. Oil-contaminated soil mixtures showed increase in mechanical properties after lime treatment and curing period. [ABSTRACT FROM AUTHOR]

Featured Application: The physical properties of heat-treated soil are clarified in this study before the soil is reused as a construction material in civil engineering. The heat treatment of oil-contaminated sites is widely carried out for the purposes of remediation. However, heat treatment changes the physical and chemical properties of soil. Before the soil can be reused as a construction material in civil engineering, such as in backfill or road base materials, the changes to its physical properties must be understood. Therefore, this study investigates the changes in the physical and chemical properties of oil-contaminated soil after heat treatment. In this investigation, experimental samples of soil with added oil from a refinery plant are used to investigate the removal rate of total petroleum hydrocarbons (TPHs) by thermal desorption and incineration. The physical properties of the soil, including water permeability and mechanical properties, are compared before and after heat treatment. The results of this study are as follows. (1) Particle size analysis reveals that heat treatment makes soil particles finer. (2) In the burning reduction test, heat treatment at 900 °C removes more than 90% of THP. (3) In the direct shear test, the friction angle (ϕ) increases with the removal rate. (4) In the hydraulic test, as the removal rate increases, the permeability coefficient increases after heat treatment. [ABSTRACT FROM AUTHOR]

In the oil-producing regions of Kazakhstan located in a climatic zone with the predominance of high temperatures, an acute problem of environmental pollution by oil hydrocarbons is noted. This work was aimed at studying the degradation of crude oil by thermotolerant oil-oxidizing strains of microorganisms isolated from the soil in Atyrau region. Oil-oxidizing microorganisms were isolated by the method of cumulative cultures. The destruction of oil was determined using the gravimetric method and gas chromatography with mass spectrometry. The identification of active strains was carried out by sequencing of the 16S rRNA gene. The research results showed that P1-35-14 and P-250-2 cultures were active at 35°C and 50°C, respectively, while K-3 culture demonstrated high activity at both temperatures. All three strains were the most actively decomposed by n-alkanes of crude oil, such as Tridecane, Dodecane, n-Heptadecane, Pentadecane, Hexadecane, n-Heneicosane, and showed good destruction activity toward aromatic compounds m-Xylene and Naphtalene. According to the results of sequencing the 16S rRNA gene, they were allocated to Rhodococcus fascians K-3, Gordonia amicalis P1-35-14, and Brevibacillus borstelensis P2-50-2 types. These strains are considered to be promising for the biological products development for bioremediation of oil-contaminated soils in an arid climate. [ABSTRACT FROM AUTHOR]

Purpose: Bioremediation is widely considered the most desirable procedure for remediation of oil-contaminated soil. Few studies have focused on the relationships among microbial community, functional genes of biodegradation, and geochemical processes during field bioremediation, which provide crucial information for bioremediation. Methods: In the current study, the microbial community and functional genes related to hydrocarbon and nitrogen metabolism, combined with the soil physico-chemical properties, were used to diagnose a set of bioremediation experiments, including bioaugmentation, biostimulation, and phytoremediation, at the field scale. Result: The results showed that the added nutrients stimulated a variety of microorganisms, including hydrocarbon degradation bacteria and nitrogen metabolism microorganisms. The functional genes reflected the possibility of aerobic denitrification in the field, which may be helpful in biodegradation. Biostimulation was found to be the most suitable of the studied bioremediation methods in the field. Conclusion: We offer a feasible approach to obtain useful bioremediation information and assist with the development of appropriate remediation procedures. The findings improve our knowledge of the interactions between microorganisms and edaphic parameters. [ABSTRACT FROM AUTHOR]

Strains isolated from high mountain industrial landfills have high biotechnological potential and studying their diversity is relevant. The objective of this study was to investigate the microbial diversity of oil-contaminated soils at a high mountain mine located 4000 meters above sea level, isolated and characterized by hydrocarbon-resistant bacteria and compare the degradation efficiency of two bacterial consortia. The surface layer (0-30 cm) that consists of 10440 mg/kg hydrocarbons were used for the experiment. A bacteria group of the three genera Pseudomonas, Flavobacterium, and Rhodococcus dominated. Fungi Aspergillus, Penicillium, and Trichoderma were present in relatively high abundances in the samples. The study shows that the actinomycetes of the Streptomyces group of the Cinereus section are most sensitive to hydrocarbon contamination. Three superior indigenous bacteria Rhodococcus rhodococcus N1, Pseudomonas fluorescens W3, and Flavobacterium NE2 has been isolated from oilpolluted soil. The consortium composed of bacteria strains Rhodococcus rhodococcus N1, Pseudomonas fluorescens W3, and Flavobacterium NE2 is more effective than a consortium composed of bacteria strains Rhodococcus rhodococcus N1, Pseudomonas fluorescens W3 hydrocarbon removal efficiency 70% and 22.9%, respectively. These findings provide highly valuable information on the production of bacterial consortium for the remediation of oil-contaminated soil. [ABSTRACT FROM AUTHOR]

The work deals with the purification process of the oil-contaminated soils. Methods of intensification of molecular surface phenomena when exposed to oil-polluted soil were shown. Removal of the oil pollutant from the surface of mineral particles is a result of a complex action of molecularsurface phenomena (selective wetting, surface energy gradient) and mechanical forces of the aqueous solution flow. In order to increase the efficiency of their purification, the work considers methods of enhancing the molecular-surface interaction phenomena effect on oil pollutant of contaminated soils. Our experiments revealed interfacial surface tensions that drop on the oil-water interface during the dilution process with an organic solvent. The organic solvent used in the process dissolves the oil contaminant, reducing its viscosity many times and formed the optimum concentration of surfactants in the oil pollutant. It found that the organic solvent and non-ionic aqueous surfactant solutions, as well as alkaline medium reduced interfacial surface tensions that lead to the enhancement of molecular-surface interaction phenomena effect on the oil pollutant of contaminated soils and raise effectiveness of their cleanup. [ABSTRACT FROM AUTHOR]

Our objective in this study was to compare the growth of zinnia, Italian ryegrass, and alfalfa, and their remediation effects in oil-contaminated soils. The soils were prepared by mixing 2, 4, or 8% diesel oil by weight with soil. The plant height and dry weights of shoots and roots were highest for zinnia in the 2 and 4% oil treatments, and highest for Italian ryegrass in the 8% oil treatment. The reduction ratios in soil total petroleum hydrocarbons concentration (TPH) for 3 plants were lower in the 4 and 8% oil treatments than those in the 2% treatment. The reduction ratios for Italian ryegrass and zinnia contaminated with 2, 4, and 8% diesel oil treatments were significantly higher than those for alfalfa and the non-cultivation treatment at 45 days after sowing, and there were no significant differences in reduction ratios between Italian ryegrass and zinnia. The reduction ratio of soil TPH concentration brought about by zinnia was also comparable to that of Italian ryegrass. Therefore, we conclude that zinnia shows growth and remediation effects that are equivalent to those of Italian ryegrass, in soils contaminated with less than 8% oil. [ABSTRACT FROM AUTHOR]

In Iraq, the risk of soil pollution by petroleum products increases with the growth of oil exploration, production and shipping large quantities of oil through pipelines over thousands of kilometers. Numerous oil spills have been documented recently in many sites due to damage in the oil industry infrastructures, which have led to soil contamination causing serious environmental hazards and deterioration to the soil and its engineering properties. So, it is essential to investigate the impact of oil leakage through the soil stratum consequently, assessing the eligibility of the contaminated soil for construction projects or identifying the appropriate treatment method. The paper investigates the general behaviour and the associated variations in the geotechnical properties upon contamination of soil in Thi-Qar Governorate which is characterised by many oil refineries. Disturbed soil samples are artificially contaminated with crude oil ranging from 0% to 10% of their dry weight. Testing programs have been conducted on the soil incorporated with conventional tests such as grading, Atterberg limit, compaction and consolidation tests as well as electrical resistivity measurements. To achieve a reliable assessment, the findings are directly compared to those of the uncontaminated soil. The final outcomes of this study indicate that an increase in oil content causes the distribution of the aggregate size curves to shift from fine to coarse ranges. Also, liquid limit, plastic limit, and plasticity index increased markedly upon contamination. Moreover, oil added to the soil mixture caused an increase in the maximum dry density of the soil and a decrease in the corresponding optimum moisture content. In addition, the consolidation characteristics of the polluted soil have been affected slightly and the electrical resistivity data was sensitive to the amount of pollutant. [ABSTRACT FROM AUTHOR]

Relationships exist between plant root growth and the phytoremediation of oil-contaminated soils. In a previous study, we demonstrated that zinnia flowers are well suited for the remediation of oil-contaminated soil. In this study, our goal was to quantify the relationship between zinnia root growth and purification of oil-contaminated soils. Three treatments were used: (1) cultivation of zinnia in oil-contaminated soil (contaminated pots), (2) cultivation in non-contaminated soil (non-contaminated pots), and (3) contaminated soil with no cultivation and only irrigation (irrigated pots). Growth of the Zinnia plants, including their roots, was significantly reduced in the contaminated pots compared with the noncontaminated pots. The soil dehydrogenase activity increased between 45 and 90 days after planting in all parts of the contaminated pots, especially the upper parts. The soil total petroleum hydrocarbon (TPH) concentrations in the contaminated pots decreased throughout the study period. Interestingly, the soil dehydrogenase activity increased, and the soil TPH concentration decreased even in lower parts of the pots where there was very little root growth. Therefore, the cultivation of plants can have a remediative effect on oil-contaminated soil even below the depth reached by the plant roots. [ABSTRACT FROM AUTHOR]

Abstract Rapid economic development has caused an increase in serious pollution problems due to the ever-increasing use of oil and its products, thus making oil pollution control an urgent task. Studies have shown that large amounts of bacterial-feeding nematodes are present in oil-contaminated soil; their function is as yet unclear. In this experiment, different densities of Caenorhabditis elegans (C. elegans) were inoculated into artificially simulated oil-contaminated soil to examine their effects on microbial activity and the microbial community in oil-contaminated soil. Six treatments were investigated: sterilized oil-contaminated soil as control 1 (FSP), nematode-free soil as control 2 (S), oil-contaminated soil (SP), oil-contaminated soil + 5, 10 or 20 individual C. elegans per gram of dry soil (i.e., SPN5, SPN10, SPN20). Results showed that oil pollution significantly increased the soil basal respiration. However, C. elegans weakened the soil basal respiration to different degrees and soil microbial respiration entropy essentially changed in line with the soil basal respiration. Oil pollution and C. elegans boosted catalase activity in contaminated soil by approximately 64.2–145.1%. Soil urease activity of SPN5, SPN10 and SPN20 was 88.5%, 126.7% and 109.0% stronger, respectively, than that of SP. The inoculation of C. elegans changed the microbial phospholipid fatty acid content in the oil-contaminated soil, including soil bacteria, fungi, actinomycetes, Gram-positive bacteria (G+) and Gram-negative bacteria (G−). Therefore, this research demonstrates that C. elegans can stimulate microbial reproduction in oil-contaminated soil, enhance related soil enzyme activities and regulate soil microbial community structure and diversity, thereby improving the contaminated soil environment and promoting oil degradation. Graphical abstract Effects of different densities of C. elegans on oil degradation. Bacterial-feeding nematodes are rich in oil-contaminated soils, but their functions remain unclear. In this study, different densities of Caenorhabditis elegans were inoculated into simulated oil-contaminated soil to examine their effects on the microbial activity and the microbial community. Results demonstrated that C. elegans addition stimulated the oil degradation and improved the repair efficiency of oil-contaminated soil. However, the magnitudes of effects did not increase as the inoculating density of C. elegans increased. Our findings suggest that C. elegans with an appropriate density would affect soil microbial growth and reproduction, thus enhancing the efficiency of oil degradation. Image 1 Highlights • C. elegans are added into soil to test the effects on microbes and oil degradation. • C. elegans and oil pollution can change the microbial activity and community. • C. elegans can promote the oil degradation in contaminated soil. [ABSTRACT FROM AUTHOR]

Graphical abstract The improvement mechanism of rapid degradation long-chain alkanes in soil by addition of fermented food waste supernatant. Highlights • Long-chain alkanes were main carbon sources for IHD after 14 days. • Long-chain alkanes were biodegraded rapidly by addition of fermented supernatant. • The glucose and acetic acid in fermented supernatant accelerated NH 4 +-N consumption. • The considerable consumed C/N promoted the grow of Acinetobacter and Aquabacterium. • The genus Aquabacterium which was uncultivable became the dominant bacteria. Abstract The objective of this study is to explore how to stimulate soil indigenous bacteria for the degradation of long-chain crude oil by adding fermented food waste supernatant (FS). Four concentrations of FS (0 mL, 0.1 mL, 1 mL, and 3 mL) were added to two oil-contaminated soils S1 and S2 for 30 days of bioremediation experiments. The results showed that the biodegradation of long-chain alkanes (C 29 - C 24) could reach up to 1756 mg/kg (49.3%, S1) and 3937 mg/kg (43.9%, S2), which were 3.1 and 3.2 times that of the non-nutrient system. In addition, the logarithmic growth rate of the indigenous hydrocarbon degraders (IHD) reached 41.5%. The long-chain crude oil can be rapidly degraded by indigenous bacteria with FS added in a short time. The glucose and acetic acid accelerated the consumption of ammonia nitrogen (NH 4 +-N) in the prophase of bioremediation and the molar ratio of consumed carbon (contained in glucose and acetic acid) to consumed NH 4 +-N (C/N) was high by adding FS. Thus, the IHD can multiply rapidly. The analysis of microbial diversity revealed that the IHD (genera Acinetobacter and Aquabacterium) became the dominant bacteria. Long-chain alkanes became the main carbon sources for IHD after 14 days in soil S1 and 16 days in soil S2. Thus, the rapid biodegradation of long-chain crude oil was achieved. The genus Aquabacterium which was uncultivable on crude oil medium became the dominant bacteria. This study provides an environment-friendly and sustainable remediation technology for bioremediation of oil-contaminated soils. [ABSTRACT FROM AUTHOR]

Oil and its derivatives contaminate many soils and not only affect their chemical and biological properties but also their geotechnical properties. As oil contamination may deteriorate the functioning of piles, this paper addresses the effects of oil contamination on soil–pile interactions. Axial compressive bearing capacities of two close-ended, instrumented piles were investigated in different oil-contaminated sand using frustum confining vessel. Three different oils (gasoil, crude oil, and used motor oil) at different contamination levels were considered and using some strain gauges, the toe, shaft, and the net total bearing capacity of piles, as well as load distributions along the pile length, were derived. The results show that the presence of oil between soil particles has considerable adverse effects on bearing capacities of model piles, especially the shaft bearing capacity. The oil viscosity and percentage, as well as the contaminated sand bed thickness around the piles, are the most influential parameters. The higher the oil viscosity and oil content, the lower the values of the piles' bearing capacities in comparison to the uncontaminated sand. With some modifications on the bearing capacity parameters of CFEM method, a good agreement was observed between measured and calculated bearing capacity values. [ABSTRACT FROM AUTHOR]

The heat treatment of oil-contaminated sites is widely carried out for the purposes of remediation. However, heat treatment changes the physical and chemical properties of soil. Before the soil can be reused as a construction material in civil engineering, such as in backfill or road base materials, the changes to its physical properties must be understood. Therefore, this study investigates the changes in the physical and chemical properties of oil-contaminated soil after heat treatment. In this investigation, experimental samples of soil with added oil from a refinery plant are used to investigate the removal rate of total petroleum hydrocarbons (TPHs) by thermal desorption and incineration. The physical properties of the soil, including water permeability and mechanical properties, are compared before and after heat treatment. The results of this study are as follows. (1) Particle size analysis reveals that heat treatment makes soil particles finer. (2) In the burning reduction test, heat treatment at 900 °C removes more than 90% of THP. (3) In the direct shear test, the friction angle (ϕ) increases with the removal rate. (4) In the hydraulic test, as the removal rate increases, the permeability coefficient increases after heat treatment.

This paper uses response surface methodology based on the Box-Behnken design to investigate the influence of substrate concentration, inoculation quantity and temperature on the biodegradation of polycyclic aromatic sulfur hydrocarbons in oil-contaminated soil by Pseudomonas sp. LKY-5. Substrate concentration is identified as the most important factor through the analysis of variance. The maximum degradation of PASHs can be achieved at the conditions of substrate concentration of 75.77 ml/kg, inoculation quantity of 20.4% and temperature of 30 °C. [ABSTRACT FROM AUTHOR]

Increasing rates of oil exploitation and utilization are associated with increasing rates of oil pollution in soil. Nematodes are abundant in soils with or without oil contamination, among which bacterial-feeding nematodes are the dominant group. However, their function in oil-contaminated soil is unclear. This study explores the effects of bacterial-feeding nematode and organic matter addition on microbial activity and oil degradation in contaminated soil. Experiments were conducted using six treatments of oil-contaminated soil: sterilized (Control), nematode-free (OC), nematode addition (OCN), nematode + wheat straw addition (OCNW), nematode + rapeseed cake addition (OCNR), and nematode + biochar addition (OCNB). At the end of a 168-day incubation experiment, the oil concentration of OCN soil was 26.77% lower than that of OC soil, and those of OCNW, OCNR, and OCNB were 12.83%, 27.81%, and 4.77% lower, respectively, than that of OCN soil. Over the experiment, soil microbial biomass carbon, fluorescein diacetate hydrolysis activity, and dehydrogenase activity increased by 4.35-382.30%, 1.75-302.22%, and − 2.73-224.55%, respectively, in oil-contaminated soils, with or without nematode and organic matter addition. These results suggest that the addition of organic matter and bacterial-feeding nematodes to oil-contaminated soil can promote the growth and activity of microorganisms that break down oil. [ABSTRACT FROM AUTHOR]

Oil products contaminate the soil in a variety of ways. In addition to environmental hazards, petroleum pollutants change the geotechnical characteristics of the soils. Clayey soils have complicated behavior in the presence of organic liquids. To better understand the behavior of oil-contaminated clayey soils, an experimental laboratory investigation was performed on illite clay soil which was polluted by different amounts of diesel (0 to 20% by soil dry weight). In this paper, geotechnical properties of clean and contaminated illite specimens consist of compaction characteristics, compressibility, shear strength parameters and unconfined compression strength were evaluated through compaction, consolidation, direct shear and unconfined compression tests respectively. Additionally, the effect of diesel on the microscopic properties of the illite was studied by scanning electron and atomic force microscopes. The findings of this study indicated a decline in maximum dry density and an increase in optimum fluid content in presence of diesel. The compressibility of the soil increased when it was exposed to the organic fluid. Adding diesel content reduced cohesion, internal friction angle and unconfined compressive strength of the soil. Considerable changes of the geotechnical parameters of illite soil in the presence of diesel indicate the necessity of study of the oil-contaminated clayey soils before the implementation of engineering projects. [ABSTRACT FROM AUTHOR]

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The result of monitoring of natural vegetation growing on oil-contaminated (2.0–75.6 g/kg) and uncontaminated (0.04–2.0 g/kg) soils of a petroleum refinery for a period of 13 years is presented. Floristic studies showed that the families Poaceae, Asteraceae, Fabaceae, and eventually Brassicaceae were predominant in the vegetation cover of both types of soils. Over time, the projective vegetation cover of the contaminated sites increased from 46 to 90%; the species diversity increased twofold: in the ecological-cenotic structure of the flora, the number of ruderal plant species decreased; and the number of steppe, i.e., zonal, plant species increased. Using 62 dominant plant species, we conducted a field study of plant characteristics such as resistance to oil pollution, the ability to enrich the rhizosphere soil with microorganisms and bioavailable mineral nitrogen, and reduction of the concentration of petroleum hydrocarbons. The results enable us to characterize the phytoremediation potential (PRP) of the native plants and identify species that, probably, played a key role in the natural restoration of oil-contaminated soils. Statistical analysis showed correlations between the PRP constituents, and the leading role of rhizosphere microorganisms in the rhizodegradation of petroleum hydrocarbons was proven. A conditional value of PRP was proposed which allowed the investigated plants to be ranked in 11 classes. The study of a large sample of plant species showed that some plants held promise for the use in reclamation of soils in arid steppe zone, and that other species can be used for the rehabilitation of saline soils and semideserts. [ABSTRACT FROM AUTHOR]

Graphene aerogel (GA) is widely studied in the oil contamination field today due its excellent adsorption properties like superhydrophobicity, high surface area, light-weight and high reusability. This study presents the effects of oil viscosity, agitation speed and oil-sand wettability on the adsorption efficiency of heavy crude oil from contaminated sand using GA. Results showed that the adsorption kinetics were best fitted with the Langmuir isotherm and pseudo-second order kinetic model indicating that the adsorption system was a two-stage process, and a monolayer adsorption route. The fitted pseudo-second order kinetic model showed that the adsorption equilibrium decreased from 12354 mg/g to 6180 mg/g with increased in crude oil viscosity from 80 cst to 380 cst, at oil-sand of wettability 4% (wt.), agitation speed of 50 rpm and room temperature of 27 °C. In addition, the highest adsorption capacity was experimentally found to occur at 4% (wt.) oil-sand wettability and agitation speed of 70 rpm, with an oil (180 cst) adsorption capacity of 11736 mg/g. On the other hand, Thus, this study showed that the GA is a promising material to improve the traditional batch extraction to remove and recover heavy crude oil from oil-wet sands. [ABSTRACT FROM AUTHOR]

Surfactant-enhanced bioremediation (SEBR) is frequently employed to clean up soil polluted with petroleum hydrocarbons, but few studies have focused on how surfactants affect microbial communities and different fractions of petroleum hydrocarbons, particularly in the field. Here, the surfactants sodium dodecyl benzene sulfonate (SDBS), alpha olefin sulfonate (AOS), Triton X-100 (TX-100), Tween80, and rhamnolipid were combined with the oil-degrading bacterium Pseudomonas sp. SB to remediate oil-contaminated soil in the laboratory. AOS gave the highest removal efficiency (65.1%) of total petroleum hydrocarbons (TPHs). Therefore, AOS was used in a field experiment with Pseudomonas sp. SB and the removal efficiency of TPHs and long-chain hydrocarbons C21–C40 reached 57.4 and 53.0%, respectively, significantly higher than the other treatments. During bioremediation the addition of Pseudomonas sp. SB significantly stimulated the growth of bacterial genera such as Alcanivorax , Luteimonas , Parvibaculum , Stenotrophomonas , and Pseudomonas and AOS further stimulated the growth of Sphingobacterium , Pseudomonas and Alcanivorax. This study validates the feasibility of surfactant-enhanced bioremediation in the field and partly reveals the mechanism of surfactant-enhanced bioremediation from the perspective of changes in different fractions of petroleum and microbial community dynamics. [Display omitted] • Surfactant-enhanced bioremediation succeeded in the field. • Surfactant promoted biodegradation of petroleum hydrocarbons, especially C21–C40 fractions. • Surfactant promoted the growth of oil-degrading bacteria. [ABSTRACT FROM AUTHOR]

Bioaugmentation (BA) of oil-contaminated soil by immobilized microorganisms is considered to be a promising technology. However, available high-efficiency microbial agents remain very limited. Therefore, we prepared a SA/GO/C5 immobilized gel pellets by embedding the highly efficient crude oil degrading bacteria Bacillus C5 in the SA/GO composite material. The optimum preparation conditions of SA/GO/C5 immobilized gel pellets were: SA 3.0%, GO 25.0 μg/mL, embedding amount of C5 6%, water bath temperature of 50°C, CaCl 2 solution concentration 3% and cross-linking time 20 h. BA experiments were carried out on crude oil contaminated soil to explore the removal effect of SA/GO/C5 immobilized pellets. The results showed that the SA/GO/C5 pellets exhibited excellent mechanical strength and specific surface area, which facilitated the attachment and growth of the Bacillus C5. Compared with free bacteria C5, the addition of SA/GO/C5 significantly promoted the removal of crude oil in soil, reaching 64.92% after 30 d, which was 2.1 times the removal rate of C5. The addition of SA/GO/C5 promoted the abundance of soil exogenous Bacillus C5 and indigenous crude oil degrading bacteria Alcanivorax and Marinobacter. In addition, the enrichment of hydrocarbon degradation-related functional abundance was predicted by PICRUSt2 in the SA/GO/C5 treatment group. This study demonstrated that SA/GO/C5 is an effective method for remediating crude oil-contaminated soil, providing a basis and option for immobilized microorganisms bioaugmentation to remediate organic contaminated soil. [Display omitted] • Sodium alginate/graphene oxide/C5 immobilized pellets (SA/GO/C5) were successfully prepared. • SA/GO/C5 immobilized pellets exhibited greatly improved mechanical properties. • SA/GO/C5 immobilized pellets promoted the removal of oil in soil. • SA/GO/C5 immobilized pellets significantly enrich crude oil degrading bacteria Alcanivorax and Marinobacter in soil. [ABSTRACT FROM AUTHOR]

A method for determination of the ecological condition of oil-contaminated soils was developed. This method is suitable for use in a wide range of oil concentrations in soil, ranging from 0–20% and provides a quantitative assessment of phytotoxicity – effective toxicity. The method involves the germination on the investigated soil (moisture 33.3%) in closed Petri dishes in the dark at +24ºС of seeds of test objects: Linum usitatissimum L., Helianthus annuus L., Fagopyrum vulgare St. We used for biotesting initial growth parameters of test objects during 5 days of growth, whenthe toxic effect of oil is quite evident, but other damaging factors do not become apparent. For each test object, an optimal oil concentration range is suggested. At low concentrations of oil in the soil 15.0% phytotoxicity is >4.0; the level of pollution – catastrophic. The method was tested on an industrial area – dumps of the Borislav Ozokerite Mine. Environmental maps of toxicity drawn up using different test objects: L. usitatissimum, H. annuus, F. vulgare were similar, which additionally confirms the correctness of the method. We recommend the application of the proposed method for identification of sites in a threatening, pre-crisis or crisis state, on which other physical-chemical studies can be further conducted.

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis , and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of –NH 2 on chitosan and –COOH on biochar, forming a new chemical bond –NH–CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%–33.09%), Bacillus (3.01%–4.10%), Dietzia (1.84%–5.56%), Pseudomonas (0–0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil. [Display omitted] • The optimal chitosan-biochar composite material was prepared for immobilized microorganisms. • A composite microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis was used. • The immobilized microorganism strategy can effectively remove crude oil from oil-contaminated soil. • The combination of material adsorption and biodegradation accelerated the remediation of oil-contaminated soil. • The chitosan-biochar composite material immobilized microorganisms reshaped the microbial community structure in soil. [ABSTRACT FROM AUTHOR]

The removal of aged hydrophobic contaminants from fine-textured soils is a challenging issue in remediation. The objective of this study was to compare the efficacy of augmentation treatments to that of biostimulation in terms of total aliphatic hydrocarbon (TAH) and toxicity removal from a historically contaminated clay soil and to assess their impact on the resident microbial community. To this aim, Pleurotus ostreatus , Botryosphaeria rhodina and a combination of both were used as the inoculants while the addition of a sterilized lignocellulose mixture to soil (1:5, w / w ) was used as a biostimulation approach. As opposed to the non-amended control soil, where no changes in TAH concentration and residual toxicity were observed after 60 days, the activation of specialized bacteria was found in the biostimulated microcosms resulting in significant TAH removal (79.8%). The bacterial community structure in B. rhodina -augmented microcosms did not differ from the biostimulated microcosms due to the inability of the fungus to be retained within the resident microbiota. Best TAH removals were observed in microcosms inoculated with P. ostreatus alone ( Po ) and in binary consortium with B. rhodina (BC) (86.8 and 88.2%, respectively). In these microcosms, contaminant degradation exceeded their bioavailability thresholds determined by sequential supercritical CO 2 extraction. Illumina metabarcoding of 16S rRNA gene showed that the augmentation with Po and BC led to lower relative abundances of Gram(+) taxa, Actinobacteria in particular, than those in biostimulated microcosms. Best detoxification, with respect to the non-amended incubation control, was found in Po microcosms where a drop in collembola mortality (from 90 to 22%) occurred. At the end of incubation, in both Po and BC, the relative abundances of P. ostreatus sequences were higher than 60% thus showing the suitability of this fungus in bioaugmentation-based remediation applications. [ABSTRACT FROM AUTHOR]

Modified Fenton’s (MF) operations affect the selectivity for MF oxidation of crude oil vs. soil organic matter (SOM) in contaminated soils; however, the mechanisms are not known. MF oxidation was tested in the lab to treat two crude oil-contaminated soils using three MF operations: (1) increasing hydrogen peroxide (H2O2) concentration, (2) enhancing iron (Fe(II)) levels, and (3) stepwise addition of H2O2rather than a single exposure. The experiments demonstrated that the selectivity for MF oxidation of crude oil in the two soils significantly decreased with a rise in H2O2and Fe(II) concentrations. The total petroleum hydrocarbon (TPH) removal efficiency in the two soils was between 40% and 50% when the concentration of H2O2was greater than 1100 mM. The limited oxidation of crude oil might possibly be attributed to poor selectivity for MF oxidation of crude oil in soils when the concentration of H2O2exceeded 1100 mM. The results indicated that sufficient Fe(II) is important for selectively removing TPH. Notably, a 25% higher removal of TPH (51%–58%) was observed in the two soils after stepwise dosing with H2O2compared with a one-step addition. Data indicated a distinct selectivity for MF oxidation of crude oil vs. SOM by stepwise addition of H2O2. In addition, the findings demonstrated a distinct selectivity for MF oxidation of SOM vs. crude oil when rapid decomposition of H2O2was present. [ABSTRACT FROM PUBLISHER]

A series of toxicity bioassays was conducted to monitor the ecotoxicity of soils in the different phases of bioremediation. Artificially oil-contaminated soil was inoculated with a petroleum hydrocarbon-degrading bacterial consortium containing Burkholderia cepacia GS3C, Sphingomonas GY2B and Pandoraea pnomenusa GP3B strains adapted to crude oil. Soil ecotoxicity in different phases of bioremediation was examined by monitoring total petroleum hydrocarbons, soil enzyme activities, phytotoxicity (inhibition of seed germination and plant growth), malonaldehyde content, superoxide dismutase activity and bacterial luminescence. Although the total petroleum hydrocarbon (TPH) concentration in soil was reduced by 64.4%, forty days after bioremediation, the phytotoxicity and Photobacterium phosphoreum ecotoxicity test results indicated an initial increase in ecotoxicity, suggesting the formation of intermediate metabolites characterized by high toxicity and low bioavailability during bioremediation. The ecotoxicity values are a more valid indicator for evaluating the effectiveness of bioremediation techniques compared with only using the total petroleum hydrocarbon concentrations. Among all of the potential indicators that could be used to evaluate the effectiveness of bioremediation techniques, soil enzyme activities, phytotoxicity (inhibition of plant height, shoot weight and root fresh weight), malonaldehyde content, superoxide dismutase activity and luminescence of P . phosphoreum were the most sensitive. [ABSTRACT FROM AUTHOR]

Bioremediation potential of the nitrogen-fixing leguminous plant Galega orientalis Lam. and its microsymbiont Rhizobium galegae was evaluated in microcosm and mesocosm scale in oil and BTEX (benzene, toluene, ethylbenzene, xylene) contaminated soils, with m-toluate serving as a model for the latter group. G. orientalis and Rhizobium galegae remained viable in m-toluate fractions up to 3000 ppm. Plant growth and nodulation were inhibited in 500 ppm m-toluate, but were restored when plants were transferred to clean medium. In soil, G. orientalis nodulated and showed good growth in 2000 ppm m-toluate as well as in diesel-contaminated soil in the field, where the plant was stimulating bacterial growth in the rhizosphere. A collection of 52 indigenous m-toluate-tolerating bacteria isolated from oil-contaminated rhizosphere of G. orientalis was characterised and identified by classical and molecular biological methods. 16SrDNA PCR-RFLP and (GTG)5-PCR genomic fingerprinting combined with partial sequencing indicated the presence of five major lineages of the Bacteria domain. A TOL plasmid-specific xylE-PCR was developed in order to detect both active and potential degraders of m-toluate. The ability to degrade m-toluate in the presence of the gene xylE was detected only within the genus Pseudomonas. The isolates were tested for capacity to grow on m-toluate as their sole carbon and energy source. In laboratory experiments, the best rhizosphere isolates performed equally well to the positive control strain and are good candidates for inoculant production in the future. They have been tagged with marker genes for further studies on colonisation and persistence.

The process improvement, a pilot remediation test and the decontamination mechanism of m icrowave- i nduced s team d istillation (MISD) for p etroleum h ydrocarbons (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". [Display omitted] • A multistage steam distillation process improved 10%∼15% removal rate. • A carbon reinforcement process shortened 50% remediation duration. • Site-scale microwave heating project achieved over 60% pollutants removal rate. • Direct microwave irradiation and low boiling point could improve removal effect. • Steam stripping, volatilization and desorption were decontamination mechanisms. [ABSTRACT FROM AUTHOR]