Oil Hydrocarbons Research Articles

DETOXIFICATION OF USED SYNTHETIC MOTOR OILS WITH BIOCOMPOSITIONS BASED ON HUMIC ACIDS IN WATER

Among the modern technologies of remediation of oil-contaminated wastewater, the most promising are technologies based on biological methods of purification, namely, on the process of self-purification using various consortia of microorganisms characterized by an increased ability to biodegrade hydrocarbons of oil and petroleum products. This article is devoted to the assessment of the detoxifying ability of new biocompositions based on microorganisms-oil destructors in combination with natural dispersants – humic acids in relation to used synthetic motor oil in water. Biocompositions based on humic acids isolated from the peat of the Tula region: reed lowland and black-alder lowland, and microorganisms-oil destructors of the genus Rhodococcus, producing biological surfactants and capable oxidizing a wide range of petroleum hydrocarbons due to the presence of enzymatic systems, have been studied. The detoxifying ability of biocompositions was determined by the method of biotesting by assessing the toxic effect on the test object duckweed small. The reduction of the toxic effect by the detoxification coefficient was achieved by more than 50%. Attention is focused on the advantages of biotesting in comparison with analytical methods, which consist in ease of use, expressiveness in determining results, cost–effectiveness and, most importantly, the ability to judge how dangerous a specific amount of xenobiotic is for the vital activity of organisms. The experiments carried out prove that the developed biocomposition affects the dispersed state of used synthetic engine oil in water, and also contributes to the degradation of its components. The obtained biocompositions can be used as complex biological products for biotechnological remediation of aquatic environments using in situ technology.

Advanced separation of mineral oil aromatic hydrocarbons by number of aromatic rings using donor-acceptor-complex chromatography to extend on-line coupled liquid chromatography-gas chromatography

An automated implementation for a subfractionation of mineral oil aromatic hydrocarbons (MOAH) into a mono-/di-aromatic fraction (MDAF) and a tri-/poly-aromatic fraction (TPAF) is presented, which is highly demanded by the European Food Safety Authority (EFSA) respecting the genotoxic and carcinogenic potential of MOAH. For this, donor-acceptor-complex chromatography (DACC) was used as a selective stationary phase to extend the conventional instrumental setup for the analysis of mineral oil hydrocarbons via on-line coupled liquid chromatography-gas chromatography-flame ionization detection (LC-GC-FID). A set of six new internal standards was introduced for the verification of the MOAH fractionation and a quantification of MDAF and TPAF, respectively. The automated DACC approach was applied to representative petrochemical references as well as to food samples, such as rice and infant formula, generally showing well conformity with results obtained by state-of-the-art analysis using two-dimensional GC (GCxGC). Relative deviations of DACC/LC-GC-FID compared to GCxGC-FID methods regarding the ≥ 3 ring MOAH content ranged between -50 and +6 % (median: -2 %, all samples, only values above limit of quantification). However, crucial deviations mainly result from “border-crossing” substances, e.g., dibenzothiophenes or partially hydrogenated MOAH. These substances can cause overestimations of ≥ 3 ring MOAH fraction during GCxGC analysis due to co-elution, which is mostly avoided using the DACC approach. Furthermore, the DACC approach can help to minimize underestimations of toxicologically relevant ≥ 3 ring MOAH caused by an unavoidable loss of MOAH during epoxidation, since natural olefins, such as terpenes, predominantly elute in MDAF, which was exemplarily shown for an olive oil and a terpene reference. The presented approach can be implemented easily in existing LC-GC-FID setup for an automated and advanced screening of MOAH to lower the need for elaborate GCxGC analysis also in routine environments.

Treatment of Acid Tars by Encapsulation to Reduce the Effects of Pollution on the Environment

Some synthesis processes obtain Acid tars after treating the refining products with sulfuric acid. They are highly toxic to the environment, occupying important storage spaces. Following the closure of the refineries in Romania, large quantities of acid tars were abandoned in oil residue tanks. Currently, activities are being carried out to inventory and dispose of them. Incineration is the only possibility to treat these wastes, which release dangerous substances into the air (CO2, SO2). That is precisely why we tried to find solutions to treat these wastes by encapsulating them with various additives, the best solution being their physical alteration through encapsulation and stabilization in situ. The results obtained from the treatment of some acid tars taken from Romania, with additives consisting of cement, sand, calcium oxide, sodium hydroxide, bentonite, and emulsifier, are presented, the created recipes being used to treat 80 collected tar samples. The effects of these recipes on the primary pollutants are also analyzed (metal content, total hydrocarbons in oil, the number of acids, cyanides, chlorides, and sulfates).

Toxicological Risk Evaluation of Polycyclic Aromatic Hydrocarbons in Soils from a Petroleum Spillage Site at Kokori in the Niger Delta Region of Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that are produced by the incomplete combustion of organic sources and are widely found in soils. This present research was carried out to evaluate the concentrations and toxicological risk assessment of the United States Environmental Protection Agency's sixteen priority polycyclic aromatic hydrocarbons (16 priority PAHs) in soils from the vicinity of an oil spillage site in Delta State of Nigeria. The level of pollution and potential toxicological health hazards of the PAHs were assessed in surface soil samples using soxhlet extraction of and Gas Chromatography-Mass Spectrometry (GC-MS). Thirteen out of the sixteen USEPA priority PAHs were detected in the soil sample. The concentrations of PAHs in the petroleum-contaminated soils in this investigation ranged from 0.01181 ppm to 1.16054 ppm, with the total estimated concentration of the 16 priority PAHs being 5.6713 ppm. Furthermore, the distribution of the PAHs in the study area was predominated by LMW PAHs (62%) over HMW PAHs (38%). Additionally, the total toxicity equivalency quotients TEQ (B[a]Peq) result of the carcinogenic potency of the USEPA priority PAHs was calculated as 0.08689 ppm (8.689%) and was discovered to be within the Canadian TEQ (B[a]Peq) threshold of 0.6 ppm. This suggests that the soil in the study area is safe based on the Canadian TEQ (B[a]Peq) standard and does not constitute a carcinogenic risk. However, the long-term bioaccumulation of these low quantities of PAHs in human has been found to constitute a potential health concern due to bioaccumulation in living systems.

Reduction strategies of polycyclic aromatic hydrocarbons in farmland soils: Microbial degradation, plant transport inhibition, and their mechanistic analysis

This study focuses on the abatement of polycyclic aromatic hydrocarbons (PAHs), a global pollutant, in farmland soils. Seven controlled PAHs in China were used as the target ligands, and four key target receptors degradable PAHs and two key target receptors transport PAHs were used as the target receptors. Firstly, the degradation abilities of the four key target receptors on PAHs were quantified, and the dominant target receptors that could efficiently degrade PAHs were screened out. Then, the co-degradation abilities of PAHs under the coexistence of the dominant target receptors (microbial diversity) were assessed, and 30 external condition-adding schemes to promote the microbial (co-)degradation of PAHs were designed. In addition, the microbial dominant target receptor mutants and the plant key target receptor mutants were obtained, the degradation and transportation of PAHs were improved by 8.06%∼22.27% and 39.86%∼45.43%. Finally, the mechanism analysis of PAHs biodegradation and transportation found that the Van der Waals interactions dominated the enhancement of PAHs’ degradation in soil, and the solvation capacity dominated the decrease of PAHs’ transportation in plant. This study aims to provide theoretical support for the prevention and control of PAHs residue pollution in farmland soil, as well as the protection of human dietary health.

PROCESSING AND RESEARCH OF EFFECTIVENESS OF NEW BIOPREPARATES BASED ON RHODOCOCCUS SP. H33, GUMATES AND LIGNOSULFONATES FOR THE CLEANING OF NEFTEZAINOUSLY CONTAMINATED SOILS

Development of preparations for increasing the efficiency of carbon deposition by woody plants in the conditions of technogenically contaminated lands is an urgent task and is divided into 2 stages. The first stage is related to the remediation of lands polluted with hydrocarbons in the process of oil production and refining. The second stage is aimed at obtaining biopreparations to accelerate carbon deposition by biosystems (woody and herbaceous plants).In this work, the effectiveness of a biopreparation based on a new strain of bacteria-oil-destructors Rhodococcus sp. H33 in combination with humates and lignosulfonates for cleaning of oil-contaminated lands was studied.It is shown that the most effective of several strains of oil destructors isolated from oil-contaminated soils is Rhodococcussp. H33, which was used as the basis of biopreparation for cleaning of lands contaminated with oil and oil products.It was found that at 8 % level of oil pollution microorganisms of the biopreparation based on strain H33 together with additives are capable of its greater destruction (the degree of biodegradation in the variant with lignosulfonates reaches 47.4 % for 6 weeks of experiment) than components separately (introduction of strain H33 without additives leads to destruction of 20 % of oil, humic preparations — does not exceed 10 %), comparison preparation «Lenoil» — 15–20 %. Based on the values of the number of heterotrophic, as well as hydrocarbon- oxidizing microorganisms, as well as the results of reducing the concentration of oil hydrocarbons, it is shown that the following composition of the complex biotechnological preparation-oil-destructor is optimal: biopreparation based on bacterial strain H33 (titer 2·109 CFU/ ml) — NPK — complex fertilizer (nitrogen, phosphorus, potassium) 0.25 g/kg soil — 0.02 % wt. sodium lignosulfonate.

Dissolution Behavior of Polycyclic Aromatic Hydrocarbons in Heavy Oil in the Presence of Supercritical Cyclohexane.

Supercritical cyclohexane (SC-cyclohexane) shows significant advantages in mild operating conditions and the modulation of product distribution. To gain insights into the upgrading process of heavy oil in SC-cyclohexane, the dissolution process of polycyclic aromatic hydrocarbons (PAHs) contained in heavy oil was simulated based on molecular dynamics with the use of naphthalene, benzopyrene, and mixtures of naphthalene and benzopyrene as the model compounds. As indicated by the radial distribution function results, in SC-cyclohexane exhibiting low density, cyclohexane formed a solvent shell around PAHs such that the local concentration was reduced and the aggregation of PAHs was inhibited. The results of the solvation free energy suggested that van der Waals forces between PAHs and cyclohexane were mainly dominant. As revealed by the dissolution process of the model compounds in SC-cyclohexane, a low density and a suitable temperature contributed to the solubilization of PAHs. An appropriate temperature and a low density can be selected for the upgrading reaction to limit coke formation.

Plant biomass extracted eco-friendly natural surfactant enhanced bio-electrokinetic remediation of crude oil contaminated soil

The current work investigates bioremediation (BIO) and electrokinetic (EK) remediation of crude oil hydrocarbons utilizing the biomass-electrokinetic (BIO-EK) approaches. The use of natural surfactants derived from plant biomass may improve remediation capacity by enhancing the solubility of organic pollutants. Sapindus mukorossi, a natural surfactant producer, was extracted from plant biomass in this study. The crude oil biodegradation efficiency was reported to be 98 %. In nature, FTIR confirms that plant biomass is lipopeptide. GCMS revealed that the crude oil (C7 – C23) was efficiently bio-degraded from lower to higher molecular weight. The application of natural surfactants in electokinetic remediation increased the plant biomass degradation of crude oil polluted soil by 98% compared to electrokinetic 55% in 2 days. Natural surfactant improves hydrocarbon solubilization and accelerates hydrocarbon electro migration to the anodic compartment, as confirmed by the presence of greater total organic content than the electrokinetic. This study proves that BIO-EK compared with a natural surfactant derived from plant biomass may be utilized to improve in situ bioremediation of crude oil polluted soils.

Cottonseed oil biodiesel used as a renewable collector for coking coal flotation

ABSTRACT Hydrocarbon oil collectors used in coking coal flotation are nonrenewable resources, and their collecting performance is difficult to meet current industry needs. In this study, cottonseed oil biodiesel (CSOB) was prepared from cottonseed oil by alkali-catalyzed transesterification, and experimental studies on flotation of 1/3 coking coal were carried out. The results showed that the clean coal yield was about 75% when the use of CSOB was 2000 g t−1. The results of contact angle, FTIR and XPS tests showed that the oxygen-containing groups of CSOB were adsorbed on the hydrophilic spots on the surface of coal particles, and the surface hydrophobicity of coal particles was increased. The ash level of the clean coal with the addition of CSOB during flotation was essentially the same as with the addition of an equivalent amount of diesel oil.

Efficient Fenton oriented oxidation of petroleum hydrocarbons in soil by regulating hydrophilic functional groups in soil organic matter

In order to reduce the ineffective consumption of hydroxyl radicals by soil organic matter, Fenton oriented oxidation was conducted after three methods of regulating the hydrophilic functional. The oriented oxidation of total petroleum hydrocarbons in the inactivated group was up to 7507.29∼ 20,764.87 mg•L/(kg•mol) with KTPH/SOM = 1.29, 0.66, which was 1.5∼ 2.7 folds that in the non-inactivated. 2 group (7820.58, 4911.50 mg•L/(kg•mol)) (KTPH/SOM = 0.43, 0.33). The results showed that highest oriented oxidation was reached in the inactivated group. Besides, from 3DEEM and FIRT, the lowest oxidation of protein I and the lowest percentage of hydrophilic functional groups in the inactivated group was 2006.66 ∼2718.93 mg/kg and 58.17∼ 62.68%, respectively, which were significantly lower than that before regulation. Above results indicated that when the ineffective consumption of hydroxyl groups by protein I was reduced with the hydrophilicity of rect soil organic matter decreasing, the efficient oriented oxidation of petroleum hydrocarbons was realized.

AN ALTERNATIVE OIL SORBENT FOR REMOVING HYDROCARBON SPILLS FROM THE WATER SURFACE

It has been studied that there is a possibility of using biomass components (crushed leaves and stems) of topinambur (Heliánthus tuberósus) as a sorption material for removing oil hydrocarbons from the water surface. Literature data on the composition of leaves and stems of topinambur are given. In laboratory conditions, the values of the maximal capacity for oils of the Devon and Carbon deposits, as well as the maximal water absorption, are determined. Oils of Carbon and Devon deposits, produced by OGPD «Leninogorskneft» PJSC «Tatneft» (Republic of Tatarstan), are studied as sorbates. The processing of topinambur biomass components with weakly concentrated (0,5–2 %) solutions of sulfuric acid has been carried out and the physicochemical parameters of the modifiers have been determined, as well as the values of the maximum oil and water absorption. It has been determined that the acid modification contributes to an increase in the maximal oil absorption index, and with an increase in the concentration of sulfuric acid in the solution, this indicator also increases. It has been found that acid treatment increases the maximum water absorption in the leaves and reduces this indicator in the stems of the plant. It has also been shown that acid treatment of topinambur stems and leaves promotes partial hydrolysis of biopolymers that make up the plant biomass components and extraction into a modifying solution, which leads, in particular, to an increase in crystallinity. Data on the efficiency of removing oil films under laboratory conditions using native and modified with 2 % sulfuric acid biomass components of Helianthus tuberósus are presented. It is shown that acid-modified leaves and stems of topinambur contribute to some increase in the efficiency of removing oil films from the water surface and reduce water absorption. It is concluded that topinambur stems, modified with a solution of sulfuric acid seem to be very effective sorption materials for removing oil films on the water surface.

Slow-release microencapsulates containing nanoliposomes for bioremediation of soil hydrocarbons contaminated

ABSTRACT Encapsulation and nutrient addition in bacterial formulations have disadvantages concerning cell viability during release, storage, and under field conditions. Then, the objective of this work was to encapsulate a bacterial consortium with hydrocarbon-degrading capacities in different matrices composed of cross-linked alginate/ polyvinyl alcohol /halloysite beads (M1, M2, and M3) containing nanoliposomes loaded with or without nutrients and evaluate their viability and release in a liquid medium, and soil (microcosmos). Also, evaluate their capacity to remove total petroleum hydrocarbons (TPH) for 165 days and matrices characterization. The encapsulate consortium showed a quick adaptation to contaminated soil and a percentage of removal (PR) of TPH up to 30% after seven days. All the matrices displayed a PR of up to 90% after 165 days. The matrix M2 displayed significant resistance to degradation and higher cell viability with a PR of 94%. This result supports the encapsulation of bacteria in a sustainable matrix supplemented with nutrients as a well-looked strategy for improving viability and survival and, therefore, enhancing their effectiveness in the remediation of hydrocarbon-contaminated soils.

Исследование интегральной токсичности почвы, загрязнённой нефтепродуктами

The effect of contamination with technical waste oil on the integral toxicity of sod-podzolic sandy loam soil under field experiment conditions was studied. The integral toxicity of the soil aqueous extract was determined using the «Ecolum» bacterial test, which is a luminescent gene-engineered Escherichia coli. Control soil samples show acceptable levels of toxicity. Soils contaminated with 10 or 20 g/kg doses of petroleum products are moderately toxic. The dose of 30 g/kg makes the soil highly toxic for luminescent microorganisms. The hydrocarbon composition of technical waste oil was determined using spectral coefficients obtained by infrared spectrometry. High content – 6.73% – of aromatic hydrocarbons (the most toxic fraction) was revealed. Correlation analysis between the soil toxicity index, the content of oil products, heavy metals (Co, Ni, Cu, Zn, Pb) and the pH of the soil aqueous extract showed a very strong positive correlation between toxicity and zinc content (r = 0.88) and oil products content (r = 0.83) in the soil, as well as a high negative correlation on soil pH (r = –0.61). The phytomass of plants growing on contaminated sites was determined. A very high inverse correlation (r = –0.82) between the content of oil hydrocarbons in the soil and phytomass confirms that soil contamination with an increased dose of oil products reduces the biomass of the aboveground part of plants. A general tendency to displacement of monocots and their replacement by dicots was observed for polluted soils.

STUDIES OF OILCONTAMINATED SOILS AND FORWARDLOOKING APPROACHES TO THEIR REMEDIATION

Milestones in the study of oilcontaminated soils at the Faculty of Soil Science for 50 years of its foundation are discussed from the prospects for the development of environmental regulation and new technologies of soil reclamation. The development of a methodological framework for the determination of oil and petroleum hydrocarbons in soils, studies of soil properties, the chemistry of oil and its components in soil and adjacent media are shown. The development of legislation on the rationing of petroleum hydrocarbons in soils is given, including the important role of the staff of Faculty of Soil Science of Moscow State University in the work out of a number of regional standards for the permissible residual content of petroleum hydrocarbons in soils is noted. The approaches to ecological rationing of oil and petroleum hydrocarbons in soils are proposed, in the aspects of natural climatic zones and the type of landuse. The importance of improving the regulatory and methodological framework and continuing work in this direction is emphasized. The necessity of research at developing technologies for reclamation of oilcontaminated lands and special use of oilcontaminated waste is indicated.

Main Factors Determining the Scale-Up Effectiveness of Mycoremediation for the Decontamination of Aliphatic Hydrocarbons in Soil.

Soil contamination constitutes a significant threat to the health of soil ecosystems in terms of complexity, toxicity, and recalcitrance. Among all contaminants, aliphatic petroleum hydrocarbons (APH) are of particular concern due to their abundance and persistence in the environment and the need of remediation technologies to ensure their removal in an environmentally, socially, and economically sustainable way. Soil remediation technologies presently available on the market to tackle soil contamination by petroleum hydrocarbons (PH) include landfilling, physical treatments (e.g., thermal desorption), chemical treatments (e.g., oxidation), and conventional bioremediation. The first two solutions are costly and energy-intensive approaches. Conversely, bioremediation of on-site excavated soil arranged in biopiles is a more sustainable procedure. Biopiles are engineered heaps able to stimulate microbial activity and enhance biodegradation, thus ensuring the removal of organic pollutants. This soil remediation technology is currently the most environmentally friendly solution available on the market, as it is less energy-intensive and has no detrimental impact on biological soil functions. However, its major limitation is its low removal efficiency, especially for long-chain hydrocarbons (LCH), compared to thermal desorption. Nevertheless, the use of fungi for remediation of environmental contaminants retains the benefits of bioremediation treatments, including low economic, social, and environmental costs, while attaining removal efficiencies similar to thermal desorption. Mycoremediation is a widely studied technology at lab scale, but there are few experiences at pilot scale. Several factors may reduce the overall efficiency of on-site mycoremediation biopiles (mycopiles), and the efficiency detected in the bench scale. These factors include the bioavailability of hydrocarbons, the selection of fungal species and bulking agents and their application rate, the interaction between the inoculated fungi and the indigenous microbiota, soil properties and nutrients, and other environmental factors (e.g., humidity, oxygen, and temperature). The identification of these factors at an early stage of biotreatability experiments would allow the application of this on-site technology to be refined and fine-tuned. This review brings together all mycoremediation work applied to aliphatic petroleum hydrocarbons (APH) and identifies the key factors in making mycoremediation effective. It also includes technological advances that reduce the effect of these factors, such as the structure of mycopiles, the application of surfactants, and the control of environmental factors.

Chemoecological Monitoring of Water Quality in the Ham Luong River (Mekong Delta, Vietnam)

Investigation of concentrations of organic and inorganic pollutants (hydrocarbons, including oil hydrocarbons, and trace elements – heavy metals and metalloids) in the Ham Luong River in the Mekong Delta was carried out and water quality was assessed by comparing the obtained levels of values with the regulatory limits of concentration. The determination of the total content of hydrocarbons and oil hydrocarbons was made by gas chromatography method; the trace elements were measured by ICP-MS technique after chemical treatment of samples. The content of oil hydrocarbons in the Ham Luong River water ranged from 0.042 to 0.076 mg/l. These values were quite high, exceeding the sanitary standard (0.05 mg/l) for fishery reservoirs, or approaching it, but they were lower compared to Vietnam national standard for domestic supply water (0.1 mg/l). The content of hydrocarbons in suspended matter was in the range of 0.011–0.37 mg/l. The concentrations of 15 trace elements were studied, nine of them (Ni, Fe, V, As, Se, Be, Cd, Sb, Tl) did not exceed any of the established regulatory limits of concentration for surface water. However, concentrations of six trace elements (Pb, Zn, Cu, Co, Ag, Mo) were found to exceed the standard regulatory limits. Among the studied 15 trace elements, critical and potentially critical elements were identified, which are subject to primary monitoring control. Chemoecological studies of water quality are important for monitoring of the ecological and sanitary water state for ensure the quality of consumed natural resources and to preserve the biological diversity of the Mekong Delta ecosystems.

Monitoring the Content of Polycyclic Aromatic Hydrocarbons in Soils and Natural Herbal Vegetation of Technogeneously Polluted Territory

Currently, one of the most important problems is the pollution of natural systems by polycyclic aromatic hydrocarbons (PAHs) as a result of human industrial activity. In this connection, it is necessary to carry out monitoring of territories subjected to the anthropogenic impact. As a result of the monitoring study of the impact zone of the fuel and energy complex enterprises, it was found that polycyclic aromatic hydrocarbons (PAHs) in the soil of the impact zone accumulate mainly up to 2 km along the line of the prevailing wind rose from the enterprise. The group composition of PAHs is dominated by 4-ring compounds, exceeding the background values by 23 times. At the same time, plants growing on the territory of the impact zone mainly accumulate such compounds as fluoranthene, pyrene, benzo[a]anthracene and phenanthrene, which is 70–82% of the total content of polyarenes in various parts of plants.

Important role of cosolvent addition and soil permeability on electrokinetic-persulfate remediation of benzo(a)pyrene

Benzo(a)pyrene (BaP) is a common soil pollutant that is difficult to remove from low-permeability soil. The effects of cosolvent and soil permeability on electrokinetic (EK) + persulfate (PS) remediation of BaP are not well understood. This study investigated BaP removal in two soil types of different low permeabilities (low: Soil-L; much lower: Soil-ML) under different types and concentrations of cosolvent-enhanced EK+PS remediation. In Soil-ML, BaP removal varied significantly, reaching up to 86.6% under EK+PS+ 5% hydroxypropyl-beta-cyclodextrin (HPCD) treatment. Compared to EK+PS alone, the promoting effect of HPCD on EK+PS increased with increased concentrations of HPCD; however, adding 1% Tween 80 (TW 80) suppressed BaP removal by 2.5–10.5% in the soil compared with that under EK+PS alone. The inhibition was further enhanced at 10% TW 80, with an average BaP removal of 36.2%. In contrast, in Soil-L, BaP removal was higher than in Soil-ML under EK+PS alone (additional 4.4–22.5%). Adding HPCD slightly inhibited BaP removal and adding 1% TW 80 had a slightly positive effect. PS migration (measured S2O82-) was impeded because of the low electroosmotic flow generated in Soil-ML, with higher clay, silt, and bound water contents. Overall, this study provides valuable insights into the EK remediation of polycyclic aromatic hydrocarbons in low-permeability soils.

Flotation kinetic tracking of sand contaminated with hydrocarbons: image analysis of pulp color changes in time

Hydrocarbon contamination in the environment represents a significant challenge. Soil remediation by flotation has been proposed as an effective approach to address this issue. This method entails the separation of hydrophobic compounds, such as soil hydrocarbons, by introducing air into a stirred reactor containing the soil pulp designated for remediation. Experiments were conducted using a 5 L Batch flotation cell to evaluate operating conditions. These experiments focused on obtaining flotation kinetics with different organic mixtures, including fine sands measuring under 150 µm. The experimental design encompassed airflow, hydrocarbon concentration, and surfactant dosage. The research utilized a diluted pulp (3% solids) with a high organic concentration (8 and 17 g/L). Flotation kinetics were measured by developing an innovative technique based on pulp colour and image processing software. This technique facilitated the tracking of concentration changes over time under Beer-Lambert's Law. Subsequently, the results were adjusted using kinetic models commonly employed in mineral flotation, including the First Order, Kelsall, and Klimpel models. This comprehensive analysis sought to elucidate the underlying phenomenology and assess the potential for industrial-scale implementation. The laboratory findings indicate the possibility of achieving recoveries of up to 86.9%, with a first-order kinetic constant of 0.73 (1/min). It is noteworthy that both the gas flow rate and the addition of surfactant exert substantial influence on this constant, consistent with the observed phenomenology of this study. Additionally, the research unveiled the impact of hydrocarbon concentration on kinetics, suggesting an additional mechanism governing hydrocarbon transport.

Distribution, Sources, and Health Risk of Polycyclic Aromatic Hydrocarbons in Farmland Soil of Helan, China

With the development of industry and agriculture, polycyclic aromatic hydrocarbons (PAHs) in the agricultural sector have gradually increased to different degrees, leading to an escalation in environmental pollution. In turn, this escalation has presented a significant possibility of endangering agricultural practices on farmland and has had a serious impact on regional sustainable development. Therefore, a total of 117 samples of soil were gathered to research the pollution level, distribution, sources, and health risk of PAHs in Helan farmland soils. A reference was used for the identification and quantification of PAH content using high-performance liquid chromatography (HPLC) with an ultraviolet detector, and their spatial distribution was analyzed utilizing the Arc Geographic Information System (ArcGIS). The source of PAHs was analyzed by absolute principal component scores/multiple linear regression (APCS-MLR). The lifetime cancer risk increment model and Monte Carlo sensitivity analysis were used to assess the potential health hazards to humans associated with PAHs in soil. Within the current study area, PAHs were higher in the northwest. The results showed that the total content of PAHs in Helan farmland soil ranged from 17.82 to 1544.73 ng·g−1 with a mean of 408.18 ng·g−1, which indicated the middle degree of pollution in farmland soil. The verification results of the APCS-MLR model showed that the correlation coefficient between the measured values and the predicted values ranged from 0.661 to 0.984, which suggested that the APCS-MLR model demonstrated favorable suitability for conducting source analysis of PAHs in the soil within the study region. Based on the contribution of PAHs from each source, the main sources of PAHs in Helan farmland soil were the combustion source (biomass, diesel, and natural gas combustion) and the transportation source (gasoline for vehicles and traffic exhaust emissions). The health risks’ estimation showed that PAHs in farmland soil did not have potential health risks for adults but represented a carcinogenic risk for children via the main exposure pathway of ingestion with the mean intake of 1.28 × 10−5. Meanwhile, the carcinogenic risks (CRs) of dermal contact for the mean value of adults (9.32 × 10−7) was found to be higher than that for children (3.18 × 10−8). From the Monte Carlo simulation, the soil particle uptake rate was the most sensitive to the health risks of children and adults with risk probabilities of 26% and 52%, and the risk probabilities from body weight were −11% and −1%, whose negative value indicated that the increase in body weight could reduce the health risks to human. These findings could provide reference for the study of soil organic pollution in Helan farmland soil and contribute significantly to the preservation of the ecological environment, maintaining human health and safety, and promoting the sustainable development of regional farmland.