Oil Hydrocarbons Research Articles

The Impact of Feed Management Technologies on Mineral Oil Hydrocarbons (MOH) Contamination: A Comparative Farm Level Approach

Legislative frameworks about contamination are often limited to foods and underestimate the role of animal nutrition for safe production. This study aims to assess mineral oil hydrocarbon (MOH) contamination in feed and identify the technological factors that are contributing to this issue, particularly focused on mechanised harvesting and processing. Three dairy farms, classified by contamination risk (low, medium, and high), were selected, and fifteen feed samples were analysed using the coupled liquid chromatography–gas chromatography–flame ionisation detection (LC–GC–FID) method, with a microwave-assisted saponification (MAS) step to determine mineral oil saturated (MOSH) and aromatic (MOAH) hydrocarbon levels. Important contamination levels were observed depending on the technological development of each farm. MOSH levels ranged from 11.4 mg/kg to 81.40 mg/kg, while MOAH levels ranged from 0.5 mg/kg to 4.6 mg/kg. MOAH accounted for 4.74% of the total MOH content. The results showed a connection between feed production technologies and MOH contamination levels. Factors such as the mechanisation, the machinery used, and the storage conditions were potentially contributors to contamination, while chemical treatments had no direct impact but some potential risks. The contamination levels varied across farms, indicating certain contamination sources beyond technological factors. Advanced technological measures and proper equipment maintenance are suggested to mitigate MOH contamination risks in feed.

Comparing theeffect of applying different types of amendments on carbon emissions and kinetics of degrading total petroleum hydrocarbons in artificial petroleum-contaminated soil.

Contamination byspent engine oil represents a significant global environmental challenge as it poses a major hazard to human health, animals, plants, microorganisms, the soil ecosystem, and aquatic ecosystems. This study assumes that some amendments differ significantly in their ability to degrade petroleum hydrocarbons. Therefore, this incubation study was conductedto investigate the effect of different types of inorganic and organic amendments (zeolite, bone char, banana leaves biochar, and wood chips biochar) on carbon emissions (CO2-C) and the kinetics of total petroleum hydrocarbons (TPHC) degradation in artificial petroleum-contaminated soil. These amendments wereadded to the soil under study at adose of 3% (w/w). At the end of the incubation period, applying zeolite, bone char, banana leaves biochar, and wood chips biochar to artificial petroleum-contaminated soil significantly reduced cumulative CO2-C emissions compared to the control. The banana leaves biochar significantly decreased TPHC concentrations in artificial petroleum-contaminated soil compared to the control treatment. At the end of the incubation period, adding banana leaves biochar to the soil showed high degradation efficiencies of TPHC which was36% higher than soil before incubation. The effectiveness of applying amendments used in this experiment on the degradation of TPHC increase was in the order of banana leaves biochar > bone char > wood chips biochar > control > zeolite. The second-order model described the kinetics of total petroleum hydrocarbons better than thefirst-order model. Banana leaves biochar added to the soil resulted in a significant increase in the degradation rate constant of total petroleum hydrocarbons (k2) compared with the control. A higher k2 value indicates that TPHC degrades more rapidly. The half-life of TPHC degradation in the soil was decreased significantly by adding banana leaves biochar. According to the second-order equation, the half-lives of control, zeolite, bone char, banana leaves biochar, and wood chips biochar were 4.0, 5.3, 2.7, 1.0, and 3.6 years, respectively. The banana leaves biochar amendment might be cheaper and more environmentally friendly than other organic amendments because it has the high potential for carbon sequestration and remediate petroleum-contaminated soil, which would increase the sustainable use of petroleum-contaminated soil leading to preserving the environment.

Solubilization of n-hexadecane by micellar solutions of trehalolipid - surfactants of biological origin

Objectives. To isolate biosurfactants of glycolipid nature produced by oil hydrocarbon degrading bacteria and to establish their ability to solubilize hydrophobic compounds in the case of n-hexadecane.Methods. Trehalolipids were isolated from bacteria Rhodococcus erythropolis X5 (VKM Ac-2532 D) and Rhodococcus erythropolis S67 (VKM Ac-2533 D) included in the MikroBak biopreparation for the bioremediation of oil-contaminated territories. The genome of R. erythropolis X5 is deposited in the National Center for Biotechnology Information database under GenBank accession numbers CP044283 and CP044284, BioSample – SAMN12818508, BioProject – PRJNA573614, and SRA – PRJNA573614. The content of trehalolipid biosurfactants was estimated by the amount of trehalose in aqueous solutions of biosurfactants using the phenolsulfur method. The surface tension of the obtained aqueous solutions of biosurfactants was determined by the du Noüy ring method using a Kruss K6 tensiometer (Kruss, Germany). The critical concentration of micelle formation was determined by the inflection point on the curves of surface tension dependence on the concentration of the biosurfactant solution. In order to establish the solubilizing ability of biosurfactants, the residual concentration of n-hexadecane in an aqueous sample of different concentrations was determined using a gas chromatographic method of analysis.Results. At a constant surface tension of 24.2 mN/m and 25.0 mN/m for R. erythropolis X5 and R. erythropolis S67, respectively, the critical micelle concentration for both strains was 33 mg/L (3.8 ∙ 10−5 mol/L). The solubilizing effect of Rhodococcus trehalolipid micellar solutions against hydrophobic n-hexadecane was demonstrated by gas chromatographic analysis. The solubilization process was characterized using molar solubilization capacity (Sm), molar solubilization ratio (MSR), micelle–water partition coefficient (Km), and solubilization energy 0 (ΔGS ). It was shown that the solubilization process of n-hexadecane proceeds spontaneously 0 (ΔGS = −35.5 kJ/mol) and more efficiently (Sm = 4.3 mol/mol, MSR = 4.7 mol/mol) than in comparison with other biosurfactants of glycolipid nature.Conclusions. Based on the value of the molar solubilization coefficient, it can be concluded that trehalolipids of the R. erythropolis X5 strain solubilize n-hexadecane in aqueous solutions to a greater extent than compared to other biosurfactants of a glycolipid nature, but are inferior to synthetic surfactants.

Environmental Impact and Decompsition of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Soils: Challenges and Future Directions

The rapid pace of urbanization and development has led to an increasing global concern over polycyclic aromatic hydrocarbons (PAHs) due to their persistent and widespread presence in the environment, posing significant threats to ecosystems and human health. PAHs originate from both natural and human-made sources and can be categorized based on their origin into pyrogenic, petrogenic, and biogenic products. Upon entering the environment, PAHs undergo various chemical and biological transformations, and their movement occurs through processes such as air-to-soil and soil-to-air transport. Composting, a green and cost-effective technology, offers a promising solution for PAH remediation. This process, which includes mesophilic, thermophilic, cooling, and maturing stages, can yield compost that is useful as fertilizer and soil amendment in agriculture. The success of composting depends on factors such as substrate bioavailability, oxygen levels, nutrient supply, and environmental conditions. While composting has shown effectiveness in reducing PAH levels, it is not without challenges, including the risk of weed infestation, greenhouse gas emissions, and odor pollution. The main obstacles in PAH remediation today are the limited bioaccessibility of PAHs and the insufficient focus on the formation of oxygenated PAHs during the process. Future research should address these challenges, particularly by improving PAH bioaccessibility and mitigating issues related to odor and greenhouse gas emissions.

CO 2 geological storage potential in the Croatian part of the Pannonian Superbasin

In the continental part of Croatia, oil and gas have been discovered in more than 60 locations. Most reservoirs are in the Neogene/Quaternary basin infill, but the largest ones are found in the basement rocks. Decades of exploration have left a significant vintage dataset and substantial knowledge of the subsurface geology and reservoir properties. Since 2005, research efforts have been redirected towards CO 2 geological storage capacity estimates, and the first results were obtained relatively quickly. All identified potential storage objects – deep saline aquifers, depleted hydrocarbon fields and oil reservoirs that are suitable for CO 2 enhanced oil recovery (CO 2 -EOR) – can be regarded as prospective. The deep saline aquifers are defined on a regional scale and their estimated capacity is the highest (2584 Mt), but this is ‘theoretical capacity’ that can only be used to outline the total resource base. The storage capacity estimated for the selected 14 depleted hydrocarbon fields sums to 143.6 Mt, and this is a viable capacity that might be developed as soon as a particular field stops with production, but the most promising storage objects are the seven fields that have reservoirs suitable for CO 2 -EOR operations. The most recent models have revealed that seven active EOR fields operating in parallel between 2025 and 2040 could store up to 1.2 Mt CO 2 a −1 , while producing c. 1.2 Mt a −1 of additional oil. This is very high for a country with only 5.5 Mt CO 2 a −1 in point sources.

Toxicity of crude oil: a systematic review of the acute impacts on Cnidaria

Cnidarians are ecosystem engineers that play a fundamental role in food webs. However, they are increasingly threatened by anthropogenic activities, such as oil spills, which can cause acute sublethal effects and in some cases, mortality. The literature on this theme is limited and fragmented, with diverse objectives and methodologies, making it challenging to identify consistent patterns and knowledge gaps. This article aims to provide a systematic review of the acute impacts of crude oil and petroleum hydrocarbons on members of the Phylum Cnidaria, to synthesize and integrate the available data. The research followed the PRISMA 2020 guidelines, and employed the search terms: “crude oil” AND “acute” AND (Cnidaria OR coral), along with the names of each Cnidarian class. The search was restricted to articles published in English from 2013 to 2023, excluding studies that did not directly address the core topic. The number of records collected was relatively low, with only 30 articles identified from 20 studies. The highest number of publications occurred in 2022, and the USA was the most represented country. The Class Anthozoa, particularly corals (Order Scleractinia) was the most studied. Research focused on the effects of crude oil on gametes, embryos, larvae and adults, with most studies examining adult organisms. The majority (56.6%), utilized mixtures of crude oil hydrocarbons, while a smaller proportion (36.6%) focused on pure aromatic hydrocarbons. Most experiments employed Water Accommodated Fractions (36.6%) and continuous flow system (20%). The most common exposure durations (30%) were 96 and 48h, with exposure times ranging from 18h to several days. There was significant variation in methodological approaches, underscoring the need for standardized protocols. Research on adult cnidarians primarily assessed health and morphology, lethality, genetic alterations, and symbiont efficiency. In contrast, studies on early life stages focused on lethality, larval metamorphosis and settlement. Overall, the results indicate that responses vary considerably, particularly concerning exposure time and oil concentration, with sublethal effects at different levels. Further studies incorporating a broader range of species, novel approaches, and the combined effects of elevated temperature and UV radiation are crucial to advancing our understanding of oil impacts on cnidarians.

Compositional Analysis of Oxygenates and Hydrocarbons in Waste and Virgin Polyolefin Pyrolysis Oils by Ultrahigh-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Compositional Analysis of Oxygenates and Hydrocarbons in Waste and Virgin Polyolefin Pyrolysis Oils by Ultrahigh-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A New Bacterial Strain Producing Both of the Surfactin and Fengycin Lipopeptide Biosurfactant with Strong Emulsifications on Crude Oil.

A new lipopeptide-producing strain Cytobacillus sp. R3-1 was isolated from the production water of the Daqing oilfield in China and identified based on 16S rRNA gene sequence analyses. The strain R3-1 is capable of simultaneously producing both of the surfactin and fengycin, the two major families of the lipopeptide biosurfactant. The chemical structures of the surfactin and fengycin were confirmed by a combination of the ESI-MS, FT-IR, and amino acid analyses, and the impact of various temperatures, pH, and NaCl concentrations on the emulsifying activity (E24) was investigated. The lipopeptide biosurfactant produced by the strain R3-1 exhibited strong emulsifying activity with E24 value over 60% on crude oil and different hydrocarbons, including the cyclohexane, hexadecane, benzene, toluene, kerosene, diesel oil, and liquid paraffin. Meanwhile, it showed excellent emulsifying activity across a broad range of conditions of the temperature up to 60 °C, NaCl tolerance up to 100 g/L, and pH values between 5 and 9, which suggests that the strain R3-1 is a valuable microbial candidate for the simultaneous production of the surfactin and fengycin lipopeptide biosurfactant with strong emulsifying properties and stability under diverse environmental conditions and is a potential application in environmental bioremediation and enhanced oil recovery.

Biodegradation kinetics of petroleum hydrocarbons by composite microbial agents combined with slow release agents in groundwater

Bioremediation of oil-polluted groundwater is often limited by the properties of oil and oligotrophic conditions in the groundwater environment, sometimes causing long biodegradation times and low biodegradation efficiencies. To clarify this issue, dominant oil-degrading bacteria and slow release agents (SRAs) were prepared and mixed to enhance the biodegradation of different oil samples and hydrocarbons in the groundwater environment. The biodegradation efficiencies of diesel oil, Venezuelan crude oil, and Jibei heavy crude oil by the consortia of bacteria increased from 33.66 %–52.21 % to 34.90 %–63.43 % when optimal nitrogen (N) and phosphorus (P) nutrients were added with SRAs. The release kinetics of N and P SRAs (NP-SRAs) followed Fickian diffusion, and the biodegradation processes of the five petroleum hydrocarbons and three oil products were all well approximated by a second-order kinetic model. The half-lives of the five hydrocarbons in the groundwater were shortened from 0.01 to 7.46 d with the NP salt directly added to 0.002–6.67 d when the NP-SRAs and oxygen SRAs were added, and they decreased from 4.85 to 34.00 d to 2.80–28.90 d for the three oil samples. This study provides insights into the biodegradation kinetics of different hydrocarbons, facilitating the development of effective microbial remediation technologies for the oil contaminated groundwater environment.

Removal and mechanism investigation of polycyclic aromatic hydrocarbons in coconut oils by ionic liquids

Removal and mechanism investigation of polycyclic aromatic hydrocarbons in coconut oils by ionic liquids

Hydrothermal liquefaction of southern yellow pine with downstream processing for improved fuel grade chemicals production

The hydrothermal liquefaction (HTL) technique for liquefying lignocellulose biomass feedstock is often associated with low biocrude yield and poor fuel properties. This study examined the HTL of southern yellow pine sawdust and the hydrotreatment (HYD) of produced biocrudes in an effort to address these challenges. Pine HTL treatment was performed within water and water–ethanol mixed reaction medium at 250, 300, and 350℃ temperatures using metallic iron (Fe) as a catalyst. The rising reaction temperature in a water medium and increasing ethanol content in a mixed reaction medium were found to be effective in enhancing the biocrude yield from the non-catalytic pine HTL process. Maximum non-catalytic biocrude yield of 18 wt.% was produced in water at 350℃, whereas the ethanol and water (1:1 on mass basis) mixture generated the highest biocrude yield of 34 wt.% at 300℃ without any catalyst. The iron catalyst facilitated a maximum of 29 wt.% of biocrude yield as opposed to 18 wt.% without the catalyst at 350℃ in water. The use of an iron catalyst also raised the calorific value of produced biocrudes by 2.5–14 % within 250-350℃ in both water and water–ethanol media. The catalytic and non-catalytic biocrude products were chosen to undergo HYD treatment at 400 °C under high hydrogen pressure (initial 1000 psi) using an alumina-supported cobalt-molybdenum catalyst. The HYD treatment reduced the oxygen content of upgraded oils by 36–60 % compared to the parent HTL biocrudes with 35–37 MJ/kg calorific values. The simulated distillation detected the maximum gasoline range compounds in upgraded oil from catalyst and water–ethanol conditions, whereas the GC–MS analysis revealed the production of increased aromatic hydrocarbons in all upgraded HYD oils. This work has demonstrated the potential of ethanol and inexpensive iron catalyst in enhancing the biocrude production from pine, which could be upgraded to better fuel using the HYD process.

Insights into the prediction uncertainty of machine-learning-based digital soil mapping through a local attribution approach

Abstract. Machine learning (ML) models have become key ingredients for digital soil mapping. To improve the interpretability of their predictions, diagnostic tools such as the widely used local attribution approach known as SHapley Additive exPlanations (SHAP) have been developed. However, the analysis of ML model predictions is only one part of the problem, and there is an interest in obtaining deeper insights into the drivers of the prediction uncertainty as well, i.e. explaining why an ML model is confident given the set of chosen covariate values in addition to why the ML model delivered some particular results. In this study, we show how to apply SHAP to local prediction uncertainty estimates for a case of urban soil pollution – namely, the presence of petroleum hydrocarbons in soil in Toulouse (France), which pose a health risk via vapour intrusion into buildings, direct soil ingestion, and groundwater contamination. Our results show that the drivers of the prediction best estimates are not necessarily the drivers of confidence in these predictions, and we identify those leading to a reduction in uncertainty. Our study suggests that decisions regarding data collection and covariate characterisation as well as communication of the results should be made accordingly.

Spatial interaction and risk zoning of compound pollutants in farmland soils: Insights from heavy metals and polycyclic aromatic hydrocarbons in Hezhang County, China

The accurate identification and assessment of comprehensive risks associated with compound pollution in agricultural ecosystems remain significant challenges due to the complexity of pollution sources, soil heterogeneity, and spatial variability. In this study, bivariate local indicators of spatial association (LISA) were applied to analyze the spatial interaction between heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in farmland soils in Hezhang County. The results revealed distinct clusters with elevated concentrations of both HMs and PAHs, predominantly in areas affected by long-standing lead-zinc mining and smelting activities. Positive matrix factorization (PMF) was utilized to identify mining and smelting activities, and associated coal consumption as common sources of both pollutants, contributing 53 % and 28 %, respectively. Ecological health risk assessment results indicated that the combined pollution in this area has led to particularly severe ecological and cancer risks, with the pollution coefficient (Pc) exceeding 3.0, and risk values for both adults and children surpassing the threshold of 10−4. Through the integration of advanced bivariate LISA mapping and thorough risk assessment, this study precisely delineated ecological risk zones (33.1 %) and more refined health risk zones (40.1 %) associated with combined pollution. The southwest of Hezhang was identified as a critical hotspot for combined pollution risks, primarily due to intensive mining and smelting activities in the region. Overall, this study underscores the utility of bivariate LISA as a robust approach for delineating spatial clustering patterns caused by combined pollutants. It provides crucial insights for identifying regions with heightened human health and ecological risks in rural settings.

Impact of petroleum contamination on soil properties in Absheron Peninsula, Azerbaijan

This study aims to assess the extent of hydrocarbon and heavy metal contamination in soils from specific areas on Azerbaijan's Absheron Peninsula, including Absheron, Suraxanı, and Baku, and to evaluate the impact of this contamination on soil properties. Soil samples were analyzed for Total Petroleum Hydrocarbons (TPH) and heavy metals, including aluminum, arsenic, cadmium, lead, and iron, alongside assessments of soil physical, chemical and biological properties. The results revealed significant contamination across all studied areas, particularly in Suraxanı, where TPH levels reached 190 ± 20 mg/kg, exceeding the environmental standard of 100 mg/kg. Similarly, Suraxanı soils exhibited alarmingly high concentrations of heavy metals, with aluminum at 30,128 ± 1,500 mg/kg, arsenic at 50.94 ± 2.5 mg/kg, and cadmium at 0.153 ± 0.01 mg/kg, all surpassing acceptable limits. These contaminants severely degraded soil health, evidenced by increased bulk density (1.7 g/cm³ in Suraxanı) and reduced soil porosity. Microbial activity, a key indicator of soil fertility, was also markedly lower in contaminated regions, with the total bacterial count in Suraxanı being less than half that of the uncontaminated area. The findings underscore the urgent need for comprehensive soil management practices and stricter environmental regulations to mitigate contamination's adverse effects and protect both ecosystems and public health in Azerbaijan’s petroleum contaminated areas.

Anaerobic Oxidation of Oil by Microbial Communities of Bottom Sediments of a Natural Oil Seepage Site (Bolshaya Zelenovskaya, Middle Baikal)

The microbial communities of bottom sediments of the Bolshaya Zelenovskaya oil seepage site (Lake Baikal) were investigated to assess their diversity and potential functional activity in the anaerobic degradation of oil. Microorganisms of the subsurface and deep sediment layers were grown in enrichment cultures supplemented with oil and various electron acceptors for 1 year at 10°C, and it was found that the concentrations of n-alkanes and polyaromatic hydrocarbons decreased by 1.2–2 and 2.2–2.8 times, respectively. Hydrocarbon conversion was accompanied by generation of hydrocarbon gases (methane and ethane). The microbial community of subsurface sediments had a higher bacterial diversity than the community of deep horizons and was composed of microorganisms specialized in degradation of a broad range of substrates, including oil hydrocarbons. The community of the deep sediment layer was dominated by Atribacterota, Caldisericota, and Bathyarchaeia (Thermoproteota), as well as members of the “rare biosphere”: Elusimicrobiota and Candidatus Hadarchaeota. Apparently, oil degradation in the bottom sediments of Lake Baikal is primarily mediated by members of the phyla Bacillota, Pseudomonadota, Chloroflexota, Actinomycetota, Desulfobacterota, Atribacterota, Halobacteriota, and Bathyarchaeia (Thermoproteota).

Hydrocarbon-Oxidizing Bacteria of the Bottom Ecotopes of the Barents and Pechora Seas

Microorganisms capable of degrading hydrocarbons are regular components of natural microbial communities and play an important role in self-purification of marine environments from oil contamination. High-throughput sequencing of the 16S rRNA gene V4 variable region was used to analyze microbial communities of the Barents and Pechora seas and of the microcosms with a spectrum of hydrocarbon substrates: oil, n-nonane, n-undecane, and phenanthrene. The Barents Sea communities of hydrocarbon-oxidizing microorganisms were characterized by predominance of the genera Pseudoalteromonas, Pseudomonas, Porticoccus, and Oleispira, while those of the Pechora Sea contained members of the genera Rhodococcus, Dietzia, Sphingorhabdus, and Hyphomonas. Pure cultures of these microorganisms were shown to utilize the major oil hydrocarbons: n-alkanes, cycloalkanes, and aromatic compounds.

Biodegradation of <i>n</i>-Alkanes in Oil-Contaminated Bottom Sediments under Bioelectrochemical Stimulation

Degradation of oil hydrocarbons artificially introduced into bottom sediments in a bioelectrochemical system of a membrane-free (silt) type was studied. Passive bioelectrochemical stimulation by means of electrodes connected by an external circuit with a resistance of 1 kΩ, with an average electric current of ~85 µA was found to cause an increase in degradation during two months from 23.0 to 57.9%. Contamination of bottom sediments with oil (1.32 g/kg) slightly decreased the current in the external circuit of the bioelectrochemical system. The relationship was revealed between the degree of oil degradation and predominant utilization of the lighter n-alkanes in the C14H30–C30H62 series, compared with both the original oil and the residual hydrocarbons of the control. An increase in the representation of the alkB alkane monooxygenase genes relative to the 16S rRNA gene in the total DNA isolated from the sediments was induced by the introduction of hexadecane, both in the case of electrochemical stimulation and in the control. The results may be of interest for the development of new methods of bioelectrochemical removal of organic pollutants from anaerobic environments.

The Impact of Green Infrastructure on the Quality of Stormwater and Environmental Risk

Increasing urbanization and the associated sealing of areas and the use of storm sewer systems for drainage not only increase the risk of flooding but also reduce water quality in streams into which stormwater is discharged. Green infrastructure (GI) measures are applied with the aim of managing this stormwater sustainably and reducing the associated risks. To this end, a quantitative–qualitative approach was developed to simulate GI—namely, rain gardens, bioretention cells, and vegetative bioswales—at the urban catchment scale. The findings highlight the potential of applying GI measures to managing stormwater more effectively in urban environments and mitigating its negative pollution-related impacts. For the housing estate analyzed, a simulated implementation of GI resulted in a reduction in pollution, measured as total nitrogen (N; 9–52%), nitrate-N (5–30%), total phosphorus (11–59%), chemical oxygen demand (8–46%), total suspended solids (13–73%), copper (12–64%), zinc (Zn; 16–87%), polycyclic aromatic hydrocarbons (16–91%), and the hydrocarbon oil index (HOI; 15–85%). Reducing the concentrations of pollutants minimizes the risk to human health determined via the HOI from a low-risk level to zero risk and reduces the ecological risk in terms of Zn pollution from a significant risk to a low risk of adverse effects. The modeling conducted clearly shows that the GI solutions implemented facilitated a quantitative reduction and a qualitative improvement in stormwater, which is crucial from an environmental perspective and ensures a sustainable approach to stormwater management. Lowering the levels of stormwater pollution through the implementation of GI will consequently lower the environmental burden of pollutants in urban areas.

Remediation of Hydrocarbons in Soil by Medicago sativa Plant

Remediation of Hydrocarbons in Soil by Medicago sativa Plant

Chronic and Periodic Effects of Smoke from Crop Residue Combustion on Soil Enzymatic Activity

Wildfires lead to the emission of large volumes of toxic smoke, which is transported hundreds of kilometres away from the fires and can have a negative impact on soil, biota and humans. A series of modelling experiments on pyrogenic fumigation of soil were carried out to assess the effects of gaseous products from wildfires on soil biochemical parameters. The effects of chronic exposure to gaseous substances and periodic, repetitive effects of smoke exposure on soil were determined. The results were compared with a single intensive smoke exposure. It was found that pyrogenic impact significantly affected the change of enzymatic activity of ordinary chernozem. The degree of influence depended on the duration and periodicity of smoke exposure. In all experiments enzymes of oxidoreductase class (catalase, peroxidase, polyphenol oxidase) were more sensitive to fumigation than invertase from hydrolase class. The reason of suppression of enzymatic activity of soils is high concentrations of toxic gases. The following concentrations exceeded the maximum permissible concentrations for atmospheric air: CO 714 times, phenol (hydroxybenzene) 441 times, acetaldehyde 24100 times, formaldehyde 190 times. Accumulation of polycyclic aromatic hydrocarbons (PAHs) in soil after fumigation was revealed, the total content of PAHs was 377 ng/g. The highest values were recorded for naphthalene, where the concentration was 4.4 times higher than the maximum permissible and phenanthrene 2.8 times higher than the maximum permissible. It was found that 60-minute intensive smoke affects the soil to a lesser extent than chronic and periodic. Indicators of enzymatic activity of chernozem after such fumigation decreased by 15-33% depending on the enzyme, in chronic and periodic by 41-84 and 31-78%, respectively. The obtained data indicate a significant effect of smoke on enzymatic activity of soils under chronic and periodic exposure to gaseous products of combustion.