Hydrocarbon Concentrations In Soil Research Articles

Total Petroleum Hydrocarbons in Soil of Different Oil Fields at Basrah Governorate, Iraq

Objectives: This study concentrated on determining the total hydrocarbon concentrations in soil at eleven stations of the oil field (Seba, Safwan, Majnoon, Ratawi, Bergezia, Qurna2, Qurna1, Shuaaba, South and North Rumaila, and Al Zubair). Methods: Soil samples were freeze-dried, finely pulverised in an agate mortar, and sieved through a 62-um metal sieve and 150 ml mixture of methanol and benzene (1:1) was used to extract the soil. Determination of TPHs where determined by using Spectrofluroscence, Total organic carbons (TOC) in the soil of the oil fields were also determined. Results: According to the TPH distribution used in this investigation, station 11 (Al Zubair) had the highest concentration of TPHs (162.53mg/g dry weight), while station 1(Seba) had the lowest concentration (21.4mg/g dry weigh). Additionally, the study's findings demonstrated that TPH levels varied spatially amongst sites. The highest amounts of total petroleum hydrocarbons detected in soil samples, as well as the findings of this investigation indicating that TPH levels varied geographically throughout stations. Conclusions: There is significant correlation between the TPH in soil and TOC%. By comprising the result concentration of this study with literature reviews, the concentration levels lies within it and in other cases exceed it.

Impact of artisanal refining activities on bacterial diversity in a Niger Delta fallow land

Hydrocarbon pollution is a major ecological problem facing oil-producing countries, especially in the Niger Delta region of Nigeria. In this study, a site that had been previously polluted by artisanal refining activity was investigated using 16S rRNA Illumina high-throughput sequencing technology and bioinformatics tools. These were used to investigate the bacterial diversity in soil with varying degrees of contamination, determined with a gas chromatography-flame ionization detector (GC-FID). Soil samples were collected from a heavily polluted (HP), mildly polluted (MP), and unpolluted (control sample, CS) portion of the study site. DNA was extracted using the Zymo Research (ZR) Fungi/Bacteria DNA MiniPrep kit, followed by PCR amplification and agarose gel electrophoresis. The microbiome was characterized based on the V3 and V4 hypervariable regions of the 16S rRNA gene. QIIME (Quantitative Insights Into Microbial Ecology) 2 software was used to analyse the sequence data. The final data set covered 20,640 demultiplexed high-quality reads and a total of 160 filtered bacterial OTUs. Proteobacteria dominated samples HP and CS, while Actinobacteria dominated sample MP. Denitratisoma, Pseudorhodoplanes, and Spirilospora were the leading genera in samples HP, CS, and MP respectively. Diversity analysis indicated that CS [with 25.98 ppm of total petroleum hydrocarbon (TPH)] is more diverse than HP (with 490,630 ppm of TPH) and MP (with 5398 ppm of TPH). A functional prediction study revealed that six functional modules dominated the dataset, with metabolism covering up to 70%, and 11 metabolic pathways. This study demonstrates that a higher hydrocarbon concentration in soil adversely impacts microbial diversity, creating a narrow bacterial diversity dominated by hydrocarbon-degrading species, in addition to the obvious land and ecosystem degradation caused by artisanal refining activities. Overall, the artisanal refining business is significantly driving ecosystem services losses in the Niger Delta, which calls for urgent intervention, with focus on bioremediation.

Polycyclic aromatic hydrocarbon concentrations in soil of three communities in Rivers State

The study was conducted in three communities in Rivers State. These communities include Okochiri community in Okrika, Mgbuodohia in Obio-Akpor and Chokocho in Etche. Soil at two different depths were sampled on a composite basis using EGASPIN 2018 procedures, extracted and analyzed for sixteen priority PAHs using US EPA 8270 (2014) procedures. Studies show the total concentration of PAHs in soil sample taken from Okochiri community in Okrika at depths of 0 - 15 cm and 15 - 30 cm was found to be 145.32 mg/kg and 101.6 mg/kg during the dry season respectively but in the wet season the total concentration was found to be 607.08 mg/kg and 242.46 mg/kg at the two depths. In Mgbuodohia, the dry season result for the two depths, showed a total concentration of 14.68 mg/kg and 27.33 mg/kg and, 16.12 mg/kg and 14.94 mg/kg in the wet season. In Chokocho, the result showed a total concentration of 4.33 mg/kg and 252 mg/kg in the dry season and 23.87 mg/kg and 10.23 mg/kg in the wet season. Result showed a higher concentration of PAHs in the tops soil (0- 15 cm) compared to the subsoil at the depth (15 - 30 cm). The total PAHs concentration was consistently higher in the wet season than in the dry season. The concentration of PAHs was found to be majorly higher in the topsoil than the subsoil both in the dry and wet season. Diagnostic ratios reveal major source to be petrogenic. The concern for the environment and humans should prompt important stakeholders to take measures that will lead to mitigate the impact of these toxic chemical.

Shaping the concentration of petroleum hydrocarbon pollution in soil: A machine learning and resistivity-based prediction method

A new method relying on machine learning and resistivity to predict concentrations of petroleum hydrocarbon pollution in soil was proposed as a means of investigation and monitoring. Currently, determining pollutant concentrations in soil is primarily achieved through costly sampling and testing of numerous borehole samples, which carries the risk of further contamination by penetrating the aquifer. Additionally, conventional petroleum hydrocarbon geophysical surveys struggle to establish a correlation between survey results and pollutant concentration. To overcome these limitations, three machine learning models (KNN, RF, and XGBOOST) were combined with the geoelectrical method to predict petroleum hydrocarbon concentrations in the source area. The results demonstrate that the resistivity-based prediction method utilizing machine learning is effective, as validated by R-squared values of 0.91 and 0.94 for the test and validation sets, respectively, and a root mean squared error of 0.19. Furthermore, this study confirmed the feasibility of the approach using actual site data, along with a discussion of its advantages and limitations, establishing it as an inexpensive option to investigate and monitor changes in petroleum hydrocarbon concentration in soil.

Using Sweet Sorghum Varieties for the Phytoremediation of Petroleum-Contaminated Salinized Soil: A Preliminary Study Based on Pot Experiments

Using energy plants to repair salinized soils polluted by petroleum is an efficient way to solve the problem of farmland reduction and prevent pollutants from entering the food chain simultaneously. In this study, pot experiments were conducted for the purposes of preliminarily discussing the potential of using an energy plant, sweet sorghum (Sorghum bicolor (L.) Moench), to repair petroleum-polluted salinized soils and obtain associated varieties with excellent remediation performance. The emergence rate, plant height and biomass of different varieties were measured to explore the performance of plants under petroleum pollution, and the removal of petroleum hydrocarbons in soil with candidate varieties was also studied. The results showed that the emergence rate of 24 of the 28 varieties were not reduced by the addition of 1.0 × 104 mg/kg petroleum in soils with a salinity of 0.31%. After a 40-day treatment in salinized soil with petroleum additions of 1.0 × 104 mg/kg, 4 potential well-performed varieties including Zhong Ketian No. 438, Ke Tian No. 24, Ke Tian No. 21 (KT21) and Ke Tian No. 6 with a plant height of >40 cm and dry weight of >4 g were screened. Obvious removal of petroleum hydrocarbons in the salinized soils planted with the four varieties were observed. Compared with the treatment without plants, the residual petroleum hydrocarbon concentrations in soils planted with KT21 decreased by 69.3%, 46.3%, 56.5%, 50.9% and 41.4%, for the additions of 0, 0.5 × 104, 1.0 × 104, 1.5 × 104 and 2.0 × 104 mg/kg, respectively. In general, KT21 had the best performance and application potential to remediate petroleum-polluted salinized soil.

Assessment of Ecological Condition of Haplic Chernozem Calcic Contaminated with Petroleum Hydrocarbons during Application of Bioremediation Agents of Various Natures

Petroleum hydrocarbon contamination disrupts ecological and agricultural soil functions. For their restoration, bioremediation agents of various natures are used (nonorganic or organic fertilizers, bacterial preparations, adsorbing agents) featuring different remediation mechanisms (adsorption or biostimulation of petroleum hydrocarbon decomposition). The objective of this research is the assessment of the ecological condition of petroleum hydrocarbon-contaminated Haplic Chernozem Calcic after the application of bioremediation agents of various natures. The influence of glauconite, nitroammophos, sodium humate, the bacterial preparation “Baikal EM-1”, and biochar on the intensity of petroleum hydrocarbon decomposition and the ecological condition of Haplic Chernozem Calcic was analyzed. The ecological condition of Haplic Chernozem Calcic was assessed based on the residual content of petroleum hydrocarbons in soil and the following biological parameters: changes in the number of soil bacteria, activity of catalase and dehydrogenases, soil respiration (CO2 emission), germinating ability, lengths of roots and shoots, and integrated index of the biological state. The minimum concentrations of residual petroleum hydrocarbons in soil were observed after the use of biochar (44% from initial content) and glauconite (49%). The biological properties of soils were affected in different ways. Soil respiration was stimulated by 3-6-fold after adding nitroammophos. Indices for the intensity of the early growth and germination of radish in soil with glauconite, sodium humate, and biochar were increased by 37–125% (p < 0.01) compared with the reference value. After the application of biochar, sodium humate, and “Baikal EM-1”, the number of soil bacteria was 66–289% higher (p < 0.01) than the reference value. At the same time, the activities of catalase and dehydrogenases were inhibited by up to 35% in variants with bioremediation agents and petroleum hydrocarbons relative to the reference values. The maximum stimulation of the biological activity (as the integrated index of the biological state (IISB)) of Haplic Chernozem Calcic was observed after applying sodium humate and biochar, with 70 and 66% (p < 0.01) increases from the reference value, respectively. Considering the net cost of bioremediation agents, the maximum cost efficiency is achieved with “Baikal EM-1”, sodium humate, and biochar: 110, 527, and 847 USD·103/ha, respectively. After using Baikal EM-1”, sodium humate, and biochar, the ecological state of Haplic Chernozem Calcic was restored.

Thermal desorption treatment of petroleum hydrocarbon-contaminated soils of tundra, taiga, and forest steppe landscapes

The results of field, analytical, and experimental research at a number of production facilities reflect the properties of oil-contaminated soils in 3 landscapes: the permafrost treeless Arctic ecosystem, boreal forest, and temperate-climate grassland-woodland ecotone. Laboratory studies have revealed the concentrations of petroleum hydrocarbons in soils, ranging from medium levels of 2000–3000 mg/kg to critical figures over 5000 mg/kg, being 2–25 times higher than the permissible content of oil products in soils. The experimentally applied thermal effects for the oil products desorption from the soil allowed finding an optimal regime: the treatment temperature from 25 to 250 °C reduces the concentrations to an acceptable value. The conditions are environmentally sound, given that the complete combustion point of humates is ca. 450 °C. The outcomes suggest the eco-friendly solution for soil remediation, preserving the soil fertility in fragile cold environments and in more resilient temperate climates, where revitalized brownfields are essential for food production.

Polycyclic aromatic hydrocarbon concentrations in soils of greenhouses located in Aksu Antalya, Turkey.

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic compounds that are generally absorbed on organic fraction of soils. It is known that some PAHs, which can pass to air, soil, water and food as a result of natural or anthropogenic processes, have carcinogenic, toxic and mutagenic effects on humans and animals. One of the important steps that is identified in the transition takes place during agricultural production. Greenhouses are commonly used as a type of agricultural production especially during the winter season in mid and temperate climates. Greenhouse cultivation is abundant in Antalya Aksu Region in Turkey. Two sampling campaigns (autumn and winter) were carried out to sample the soils in 53 glass and polyethylene covered greenhouses. The samples were analysed with gas chromatography-mass spectrometry (GC/MS) for 16 PAHs. The result showed that four ring PAHs were dominant in the region. In the winter season, PAHs concentrations increase because of low volatility of motor vehicle exhaust related PAHs in the atmosphere and of coal and wood combustion emissions used in the heating of greenhouses and surrounding village houses. The cross plots of diagnostic ratios also confirmed coal and wood combustion and traffic emissions in the region.

Phytoremediation of Oil-Contaminated Soils by Combining Flowering Plant Cultivation and Inoculation with <i>Acinetobacter junii</i> Strain M-2

Oil contamination of the soil by petroleum products has become an enormous environmental problem. In this study, we examined whether remediation of oil-contaminated soils by cultivating three flowering plants (Mimosa, Gazania, and Zinnia) could be enhanced by inoculation with Acinetobacter junii strain M-2 at different plant growth stages (at sowing, at early growth, and at mid-growth). The growth of Zinnia cultivated in oil-contaminated soils inoculated at sowing was significantly superior to that in the non-inoculated soil. Although total petroleum hydrocarbon concentrations in soils inoculated at sowing were nominally lower than those in non-inoculated soils, especially in the case of Zinnia planting, the effect did not reach statistical significance. However, dehydrogenase activity was significantly higher in the soils inoculated with A. junii strain M-2 than in non-inoculated soils for all three plant species tested. These results demonstrate that a combination of ornamental plant cultivation (particularly Zinnia) and inoculation with A. junii strain M-2 increases the efficiency of oil-contaminated soil phytoremediation.

Environmental Assessment of Polycyclic Aromatic Hydrocarbon Concentrations in soil at AL - zubaidiya Thermal Power Plant.

Polycyclic aromatic hydrocarbons (PAHs) were measured in soil samples, which collected for the period from January to August 2017, in Baghdad city, at AL-zubaidiya Thermal Power Plant. Soil samples were extracted by the soxhlet apparatus using mixture of acetone and hexane (1:1), and analyzed by GC/FID apparatus.The results show that the sixteen polycyclic aromatic hydrocarbon concentrations were varied in the two seasons. The most abundant compound in winter was naphthalene, while in summer season were naphthalene, acenaphthene, fluorene, pyrene and benzo[a]anthracene. The distribution of PAHs that have different aromatics ring, where the 2-rings are dominant in the winter season, while 2-rings, 3-rings, 4-rings are exists in summer season.

Biodegradation of High Concentrations of Aliphatic Hydrocarbons in Soil from a Petroleum Refinery: Implications for Applicability of New Actinobacterial Strains

At present, there is great demand for new resistant and metabolically active strains of biodegrading bacteria capable of degrading high concentrations of petroleum pollutants. In this study, we undertook a series of pot-based biodegradation experiments on soil from a petroleum refinery lagoon heavily polluted with aliphatic hydrocarbons (81.6 ± 2.5 g·kg−1 dry weight) and metals. Periodical bioaugmentation with either a mixture of isolated degraders identified as Bacillus sp. and Ochrobactrum sp. or biostimulation with nutrient medium, singly or in combination, did not produce any significant decrease in hydrocarbons, even after 455 days. Inoculation with Gordonia rubripertincta CWB2 and Rhodococcus erythropolis S43 in iron-limited media, however, resulted in a significant decrease in hydrocarbons 45 days after bioaugmentation. These actinobacterial strains, therefore, show significant potential for bioremediation of such highly polluted soils.

Reducing leachable petroleum hydrocarbon concentration in weathered fuel oil contaminated soil by chemical oxidation with hydrogen peroxide

Number 6 fuel oil is one of the most used energy sources for electricity generation. However, leaks can contaminate soil and also groundwater due to leaching. At old sites, the oil may have low toxicity but still contaminate groundwater with foul-tasting compounds even at low concentrations. The purpose of this study was to evaluate the feasibility of applying H2O2 to reduce the leaching potential of a fuel oil contaminated soil. A silt-loam soil was collected from a contaminated thermal-electric plant with a hydrocarbon concentration of 3.2% in soil producing 4.3 mg/l in leachate. Hydrogen peroxide was applied (0.1, 0.2, 0.3, 0.6, 1.2% dry weight basis), and petroleum hydrocarbons were measured in soil and leachate pre- and post-treatment (72 h). At first, the soil and leachate concentrations diminished linearly (24.4 and 27.3% in soil and leachate, respectively). This was followed by a phase in which the concentration in leachate diminished greatly (75.8%) although the concentration in soil was reduced only moderately (15.1%). Overall, hydrocarbons in leachates were reduced 82.4% even though concentrations in soil were only reduced 35.8%. Correlation analysis showed that at only 1.0% w/w H2O2 a concentration of petroleum hydrocarbons in leachate safe for human consumption (≤ 1 mg/l) could be obtained even with a final hydrocarbon concentration in soil > 2%. Thus, this study presents an alternative strategy for remediation of fuel oil contaminated soils in urban environments that protects water sources by focusing on contamination in leachates, without spending extra financial resources to reduce the hydrocarbon concentration in low-toxicity soil.

Анализ методов очистки нефтезагрязненных почв при авариях на объектах нефтегазовой отрасли и транспорте

Objective: Environment contamination with oil and concomitant contaminants is a burning environmental issue in many parts of Russia. Oil contamination has an effect on the overall set of soil morphological, physical, physicochemical and biological characteristics that govern its fertile and ecological functions. To reach a higher environmental safety level in the Russian oil and gas industry and transport, a multiple factor assessment of the existing oil-contaminated soil cleaning methods has been performed. Methods: Comparison of the existing oil-contaminated soil cleaning methods: mechanical, physicochemical and biological ones. Based on the systems analysis methods, phytoremediation is found to have a high potential for cleaning soils and groundwater contaminated with hydrocarbons as the above method is as a rule cheaper than any alternative soil cleaning methods. Plants do not deteriorate soil or add any secondary pollution as compared with conventional methods. In addition, the public has a positive attitude towards phytoremediation regarding it as an eco-friendly approach to cleaning contaminated soils. Results: Basic physiological and biochemical processes in plants causing a lower hydrocarbon concentration in soil are discussed. Criteria for selection of plants for phytoremediation are identified. The primary limitations on use of phytoremediation include a long soil remediation period, a significant impact of local climatic and hydrological conditions on plant growth, a plant exposure area is limited to less than 0.9 m from the soil surface (root layer), by an impossibility of growing plants in heavily contaminated soils, and also probable ingress of contaminants into food chains. It is shown that large-scale implementation of the method is held back as the method mechanisms are not sufficiently investigated. Practical importance: Phytoremediation is found to have a high potential for cleaning oil-contaminated soils and groundwater.

Accumulation of polycyclic aromatic hydrocarbons in soils and plants of the tundra zone under the impact of coal-mining industry

Thirteen polycyclic aromatic hydrocarbon (PAH) compounds were identified in organic horizons of tundra surface-gleyed soils ( Histic Stagnosols (Gelistagnic) and plants. The total content of PAHs in contaminated soils exceeded the background values by three times. Concentrations of low-molecular weight hydrocarbons in soils at different distances from the coalmines were relatively stable. Concentrations of highmolecular weight hydrocarbons had a distinct maximum at a distance of about 0.5 km from the source of emission. The increased values of correlation coefficients were found between PAH concentrations in organic soil horizons, plants, and coal of the Vorkutinskaya mine. Mostly low-molecular weight structures predominated in the organic soil horizons and in the studied plant species. The maximum capacity for the biological accumulation of PAHs was displayed by Pleurozium schreberi and the minimum capacity was displayed by Vaccinium myrtillus. Mosses and lichens actively absorbed polyarenes from the surface; most of the PAHs were transported into the plants. This phenomenon was not observed for Vaccinium myrtillus Concentrations of PAHs on the surface and in plant tissues decreased with an increase in the distance from the mine. Distribution of polyarenes in plant organs was nonuniform. Insignificant excess of concentration of polyarenes was found in dead part of Pleurozium schreberi in comparison with its living part. The accumulation of polyarenes in the leaves of Vaccinium myrtillus was higher than that in its stems and roots.

Treatment of soil co-contaminated with inorganics and petroleum hydrocarbons using silica: Implications for remediation in cold regions

Successful remediation of contaminated land in cold regions is challenged by freeze-thaw cycling, slow rates of natural hydrocarbon attenuation, extreme weather and financial and logistical constraints. At sites co-contaminated with metals and petroleum hydrocarbons, microbial activity is suppressed and biodegradation of petroleum hydrocarbons is also slowed. This study assesses the performance of eight silica treatments for immobilising inorganics (Al, Cr, Fe, Ni, Cu, Zn, As, Cd and Pb) and encapsulating petroleum hydrocarbons (a winterised diesel) in co-contaminated soil at 2°C. Treatments containing orthophosphoric acid immobilised Cu, Zn, Cd and Pb, but mobilised As. The formation of hydroxypyromorphite, sodium aluminosilicates and calcium bearing minerals were observed following treatment, demonstrating the potential for successful immobilisation of inorganics using silica treatments. Silica treatments were less effective at reducing total extractable concentrations of petroleum hydrocarbons in soil, indicating that further research is required to optimise treatment performance in soil co-contaminated with inorganics and petroleum hydrocarbons.

Consistency between health risks and microbial response mechanism of various petroleum components in a typical wastewater-irrigated farmland

Various petroleum components possess distinctive migration and toxicity characteristics. Evaluation of contamination levels on the basis of total concentrations of petroleum hydrocarbons in soil and groundwater is limited. Hunpu, a typical wastewater-irrigated area, is located at the southwest of Shenyang City, Liaoning Province, China. In this study, various fractions, exposure pathways, and soil microbial communities were taken into account to make petroleum contamination evaluation more effective and precise in the region. The concentrations and hazard quotients of aliphatic fractions, as the bulk of an oil, verified that the groundwater must not be drunk directly. The total concentrations of aliphatic hydrocarbons (TAHs) for C10–34 were 68.90–199.87 μg g−1 in soil in Hunpu, which required cleanup according to Oklahoma criteria. However, both health and ecological risks indicated that petroleum contamination in surface soil was not serious. Microbes may use aliphatic fractions as carbon and energy source for their growth, which was indicated by positive correlation between them. TAHsC12–16 posed highest human health risks and had the most significant effect on the soil microbial composition, although its concentration was low in both the groundwater and the soil. Straight-, branched-chain saturated, and cyclopropyl phospholipid fatty acids had more closely positive correlation with TAHsC12–16, which indicated that regulation of bacterial membrane fluidity to toxic petroleum pollutants. This study can also provide the guidelines for assessment and management of petroleum contamination.

Phytoremediation of contaminated soils containing gasoline using Ludwigia octovalvis (Jacq.) in greenhouse pots.

Greenhouse experiments were carried out to determine the phytotoxic effects on the plant Ludwigia octovalvis in order to assess its applicability for phytoremediation gasoline-contaminated soils. Using plants to degrade hydrocarbons is a challenging task. In this study, different spiked concentrations of hydrocarbons in soil (1, 2, and 3g/kg) were tested. The results showed that the mean efficiency of total petroleum hydrocarbon (TPH) removal over a 72-day culture period was rather high. The maximum removal of 79.8% occurred for the 2g/kg concentration, while the removal rate by the corresponding unplanted controls was only (48.6%). The impact of gasoline on plants included visual symptoms of stress, yellowing, growth reduction, and perturbations in the developmental parameters. The dry weight and wet weight of the plant slightly increased upon exposure to gasoline until day 42. Scanning electron microscopy (SEM) indicated change to the root and stem structure in plant tissue due to the direct attachment with gasoline contaminated compared to the control sample. The population of living microorganisms in the contaminated soil was found to be able to adapt to different gasoline concentrations. The results showed that L. octovalvis and rhizobacteria in gasoline-contaminated soil have the potential to degrade organic pollutants.

Determination of heavy metals and polycyclic aromatic hydrocarbon concentrations in soil and in the leaves of plant (Eucalyptus) of selected locations at Kirkuk—Iraq

The average concentrations of heavy metals (Pb, Cu, Ni, Cr, and Cd) with the polycyclic aromatic hydrocarbon (PAH) concentrations in soil and in the leaves of plant (Eucalyptus) at Kirkuk Oil Refinery and around were determined in 15 selected locations using GPS. The pickings up of samples were carried out in two periods in October 2010 and March 2011. The heavy metal concentrations in soil were relatively higher in March than in October, while the reverse was true for the heavy metal concentrations in the leaves of plant (Eucalyptus); they were relatively lower in March than in October. It is believed that such finding is obvious due to high wind speed and rainfall during the winter months (i.e., March) which wash and remove the pollutants from the air and the leaves to the soil. “Compared with results of other studies, the concentration levels of determined heavy metals show values within or lower than these studies’ results, except for the concentration of Cd in soil which was higher at the two periods were higher. The average concentrations of polycyclic aromatic hydrocarbons (PAHs) in soil indicate 3.5 ppb in October, while in March 14.2 ppb, while in the leaves of plant (Eucalyptus) indicate 37.1 ppb in October, while in March 165.2 ppb. The model of cumulative effect of heavy metals and PAHs, for soil and the leaves of plant (Eucalyptus) which were determined by geographic information systems (GIS) for both sampling periods, show distribution of concentration toward wind directions and away from the site of Kirkuk Oil Refinery e.g., SW direction. This indicates the meteorological conditions represented by the wind direction and the rainfall, which plays an important role in distribution and deposition of pollutant metals.

Phytoremediation of Crude Oil Contaminated Soil with <i>Axonopus compressus</i> in the Niger Delta Region of Nigeria

The study assessed the effectiveness of carpet grass (Axonopus compressus) in the phytoremediation management of oil impacted soil in Ubeji and Alesa Eleme communities of Niger Delta region of Nigeria. To achieve this, the study employed an experimental research design that involved the use of Axonopus compressus in the management of oil-impacted soil sites of Ubeji and Alesa Eleme. This experiment lasted for four months’ period (one planting season). Axonopus sp. was used for the treatment of the crude oil impacted sites. Laboratory analysis of the soil samples was conducted to determine the effect of phytoremediation on hydrocarbon, acidity, organic matter and moisture loss in oil impacted sites. The study revealed that the use of Axonopus sp. resulted in 66% loss of hydrocarbon from crude oil-impacted soils of Ubeji and Alesa Eleme. However, there is no significant difference in crude oil loss in the soils of Ubeji and Alesa Eleme as a result of Axonopus sp. This could be ascribed to the similarities in soil properties and climate type of the Niger Delta region of Nigeria. It also showed that the growth of Axonopus sp. in the crude oil-impacted soils of Ubeji and Alesa Eleme has reduced the acidity of hydrocarbon content in soils (4.46 - 6.87 pH in Ubeji and 4.66 - 6.86 pH in Alesa Eleme) from the first day to the 90th days of experiment, and thereafter there was stabilization at the 4th month. This indicates that acidity in soil increases (lower pH) with increase in the concentration of crude oil in soils. However, the adoption of Axonopus sp. in hydrocarbon-impacted soils has increased the pH of soils, and enhanced the accumulation of organic matter and moisture content in oil-impacted soils of Ubeji and Alesa Eleme. The implication of the findings is that Axonopus sp. has the tenacity to phytoremediate hydrocarbon concentration in soil effectively in any geographical region of the world; as such, it is recommended for adoption by oil companies, government and non-governmental organization agency for the remediation of oil spill sites.

Solid waste decontamination by thermal desorption and catalytic oxidation methods

AbstractCombined thermal desorption and catalytic oxidation for soil decontamination was studied at the pilot plant scale. Gasoline, xylene, and 2-methylnaphthalene were used as model contaminants in the concentrations from 2 g to 10 g per kg of soil. To guarantee the flow of the exhaust gas from the thermal desorption unit into the catalytic oxidation unit, a Venturi pump was used. Based on the laboratory scale catalytic tests, the commercial catalyst EnviCat® VOC-1544 was employed in the catalytic oxidation. Residual concentrations of hydrocarbons in soil after the thermal desorption were below the detection limits of the applied analytical method (GC-MS). Although the contaminant concentrations at the inlet of the catalytic reactor significantly varied during the experiments, the efficiency of catalytic oxidation was higher than 90 % in all cases.