25 years monitoring of PAHs and petroleum hydrocarbons biodegradation in soil

PAHs as environmental pollutants and their neurotoxic effects

Polycyclic aromatic hydrocarbons (PAHs), which are widely present in incompletely combusted air particulate matter <2.5 μm (PM2.5), tobacco and other organic materials, can enter the human body through various routes and are a class of environmental pollutants with neurotoxic effects. PAHs exposure can lead to abnormal development of the nervous system and neurobehavioral abnormalities in animals, including adverse effects on the nervous system of children and adults, such as a reduced learning ability, intellectual decline, and neural tube defects. After PAHs enter cells of the nervous system, they eventually lead to nervous system damage through mechanisms such as oxidative stress, DNA methylation and demethylation, and mitochondrial autophagy, potentially leading to a series of nervous system diseases, such as Alzheimer's disease. Therefore, preventing and treating neurological diseases caused by PAHs exposure are particularly important. From the perspective of the in vitro and in vivo effects of PAHs exposure, as well as its effects on human neurodevelopment, this paper reviews the toxic mechanisms of action of PAHs and the corresponding prevention and treatment methods to provide a relevant theoretical basis for preventing the neurotoxicity caused by PAHs, thereby reducing the incidence of diseases related to the nervous system and protecting human health.

AQUA-GAPS/MONET-Derived Concentrations and Trends of PAHs and Polycyclic Musks across Global Waters

Polycyclic aromatic hydrocarbons (PAHs), released from petrogenic, pyrogenic or diagenetic sources (degradation of wood materials), are of global concern due to their adverse effects, and potential for long-range transport. While dissolved PAHs have been frequently reported in the literature, there has been no consistent approach of sampling across water bodies. Passive samplers from the AQUA/GAPS-MONET initiative were deployed at 46 sites (28 marine and 18 freshwater), and analyzed for 28 PAHs and six polycyclic musks (PCMs) centrally. Freely dissolved PAH concentrations were dominated by phenanthrene (mean concentration 1500 pg L-1; median 530 pg L-1) and other low molecular weight compounds. Greatest concentrations of phenanthrene, fluoranthene, and pyrene were typically from the same sites, mostly in Europe and North America. Of the PCMs, only galaxolide (72% of samples) and tonalide (61%) were regularly detected, and were significantly cross-correlated. Benchmarking of PAHs relative to penta- and hexachlorobenzene confirmed that the most remote sites (Arctic, Antarctic, and mountain lakes) displayed below average PAH concentrations. Concentrations of 11 of 28 PAHs, galaxolide and tonalide were positively correlated (P < 0.05) with population density within a radius of 5 km of the sampling site. Characteristic PAH ratios gave conflicting results, likely reflecting multiple PAH sources and postemission changes.

Third-order calibration applied to process surfactant-modulated excitation-emission matrix four-way fluorescence data for the direct determination of four polycyclic aromatic hydrocarbons in oilfield produced water

Fluorescence spectroscopy is a powerful tool to determine polycyclic aromatic hydrocarbons (PAHs) owing to the strong endogenous fluorescence of these compounds. However, the presence of unknown interferences and overlapped spectra hinders the accurate determination of PAHs in oilfield produced water. Moreover, surfactants frequently coexist in oilfield produced water and will seriously affect the fluorescence signals of PAHs. Herein, a new methodology applying third-order calibration to process four-way (4D) fluorescence data was proposed to solve these problems and achieve accurate determination of pyrene, fluorene, phenanthrene, and fluoranthene as an example in oilfield produced water. The methodology is based on excitation-emission matrix fluorescence modulated by different concentrations of sodium dodecyl benzene sulfonate (SDBS) in the analyzed samples. The 4D fluorescence data were processed by third-order calibration methods including four-way parallel factor analysis (4-PARAFAC) and alternating weighted residue constraint quadrilinear decomposition (AWRCQLD), and the results were compared with those of second-order calibration methods. It was proved that third-order calibration was capable of accurately identifying and quantifying PAHs together with SDBS in oilfield produced water, which has better quantitative results and figures of merit compared to second-order calibration. This study provided a new approach to generating 4D fluorescence data and opened up an avenue for the accurate determination of PAHs in complex oilfield produced water with surfactants.

A novel encapsulation of 16 polycyclic aromatic hydrocarbons in petroleum sludge with palm oil fuel ash binder; an optimization study and sensitivity analysis using machine learning application

Palm oil fuel ash (POFA) has limited use as a fertilizer, while contribute effectively to the environmental contamination and health risks. Petroleum sludge poses a serious effect on the ecological environment and human health. The present work aimed to present a novel encapsulation process with POFA binder for treating petroleum sludge. Among 16 polycyclic aromatic hydrocarbons, four compounds were selected for the optimization of encapsulation process due to their high risk as carcinogenic substrates. Percentage PS (10-50%) and curing days (7-28 days) factors were used in the optimization process. The leaching test of PAHs was assessed using a GC-MS. The best operating parameters to minimize PAHs leaching from solidified cubes with OPC and10% POFA were recorded with 10% PS and after 28 days, at which PAH leaching was 4.255 and 0.388 ppm with R² is 0.90%. Sensitivity analysis of the actual and predicted results for both the control and the test (OPC and 10% POFA) revealed that the actual results of the 10% POFA experiments have a high consistency with the predicted data (R² 0.9881) while R² in the cement experiments was 0.8009. These differences were explained based on the responses of PAH leaching toward percentage of PS and days of cure. In the OPC encapsulation process, the main role was belonged to PS% (94.22%), while with 10% POFA, PS% contributed by 32.36 and cure day contributed by 66.91%.

A Comprehensive Review on the Excitation-Emission Matrix Fluorescence Spectroscopic Characterization of Petroleum-Containing Substances: Principles, Methods, and Applications

Petroleum-containing substance (PCS) is a general term used for petroleum and its derivatives. A comprehensive characterization of PCSs is crucial for resource exploitation, economic development and environmental protection. Fluorescence spectroscopy, especially excitation-emission matrix fluorescence (EEMF) spectroscopy, has been proved to be a powerful tool to characterize PCSs since its remarkable sensitivity, selectivity, simplicity and high efficiency. However, there is a lack of systematic review focusing on this field in the literature. This paper reviews the fundamental principles and measurements of EEMF for characterizing PCSs, and makes a systematic introduction to various information mining methods including basic peak information extraction, spectral parameterization and some commonly used chemometric methods. In addition, recent advances in applying EEMF to characterize PCSs during the whole life-cycle process of petroleum are also revisited. Furthermore, the current limitations of EEMF in the measurement and characterization of PCSs are discussed and corresponding solutions are provided. For promoting the future development of this field, the urgent need to build a relatively complete EEMF fingerprint library to trace PCSs, not only pollutants but also crude oil and petroleum products, is proposed. Finally, the extensions of EEMF to high-dimensional chemometrics and deep learning are prospected, with the expectation of solving more complex systems and problems.

Influence of Soil Moisture on Bioaccumulation, Growth, and Recruitment of Folsomia candida Exposed to Phenanthrene-Polluted Soil

Climate change has resulted in an increased occurrence of summer droughts in large parts of the world. Low soil moisture has marked impacts on the physiology of soil invertebrates and lowers degradation rates of organic contaminants in soil. Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic contaminants that readily accumulate in the lipids of soil organisms. Here, we exposed springtails (Collembola, small soil living arthropods) to phenanthrene (a common PAH) in combination with a range of soil water contents to investigate the combined effects of these factors on the bioaccumulation, survival, recruitment, and body growth in a full factorial experiment. The results showed that phenanthrene up to 60 mg/kg dry soil had moderate effects on survival (<20%), whereas dry soil (4% soil water content) caused approximately 60% mortality. The bioaccumulation of phenanthrene increased almost 3-fold when soil water content decreased from 22 to 4%. We observed a joint effect of low soil water content and phenanthrene on recruitment, suggesting a synergistic interaction. The recruitment EC50 values of phenanthrene decreased from approximately 40 mg/kg dry soil at 22% soil water content to approximately 10 mg/kg dry soil at 12% soil water content. Our results show that the effects of phenanthrene are more pronounced in dry soil partly because bioaccumulation is enhanced when soils become dry.

Review on carbon-based adsorbents from organic feedstocks for removal of organic contaminants from oil and gas industry process water: Production, adsorption performance and research gaps

Large amounts of process water with considerable concentrations of recalcitrant organic contaminants, such as polycyclic aromatic hydrocarbon (PAHs), phenolic compounds (PCs), and benzene, toluene, ethylbenzene, and xylene (BTEX), are generated by several segments of oil and gas industries. These segments include refineries, hydraulic fracturing (HF), and produced waters from the extraction of shale gas (SGPW), coalbed methane (CBMPW) and oil sands (OSPW). In fact, the concentration of PCs and PAHs in process water from refinery can reach 855 and 742 mg L^-1, respectively. SGPW can contain BTEX at concentrations as high as 778 mg L^-1. Adsorption can effectively target those organic compounds for the remediation of the process water by applying carbon-based adsorbents generated from organic feedstocks. Such organic feedstocks usually come from organic waste materials that would otherwise be conventionally disposed of. The objective of this review paper is to cover the scientific progress in the studies of carbon-based adsorbents from organic feedstocks that were successfully applied for the removal of organic contaminants PAHs, PCs, and BTEX. The contributions of this review paper include the important aspects of (i) production and characterization of carbon-based adsorbents to enhance the efficiency of organic contaminant adsorption, (ii) adsorption properties and mechanisms associated with the engineered adsorbent and expected for certain pollutants, and (iii) research gaps in the field, which could be a guidance for future studies. In terms of production and characterization of materials, standalone pyrolysis or hybrid procedures (pyrolysis associated with chemical activation methods) are the most applied techniques, yielding high surface area and other surface properties that are crucial to the adsorption of organic contaminants. The adsorption of organic compounds on carbonaceous materials performed well at wide range of pH and temperatures and this is desirable considering the pH of process waters. The mechanisms are frequently pore filling, hydrogen bonding, π-π, hydrophobic and electrostatic interactions, and same precursor material can present more than one adsorption mechanism, which can be beneficial to target more than one organic contaminant. Research gaps include the evaluation of engineered adsorbents in terms of competitive adsorption, application of adsorbents in oil and gas industry process water, adsorbent regeneration and reuse studies, and pilot or full-scale applications.

Comprehensive Multi-compartment Sampling for Quantification of Long-Term Accumulation of PAHs in Soils

Long-term accumulation in the soils of ubiquitous organic pollutants such as many polycyclic aromatic hydrocarbons (PAHs) depends on deposition from the atmosphere, revolatilization, leaching, and degradation processes such as photolysis and biodegradation. Quantifying the phase distribution and fluxes of these compounds across environmental compartments is thus crucial to understand the long-term contaminant fate. The gas-phase exchange between soil and atmosphere follows chemical fugacity gradients that can be approximated by gas-phase concentrations, yet which are difficult to measure directly. Thus, passive sampling, measured sorption isotherms, or empirical relationships to estimate sorption distribution have been combined in this study to determine aqueous (or gas) phase concentrations from measured bulk concentrations in soil solids. All these methods have their strengths and weaknesses but agree within 1 order of magnitude except for ex situ passive samplers employed in soil slurries, which estimated much lower concentrations in soil water and gas likely due to experimental artifacts. In field measurements, PAH concentrations determined in the atmosphere show a pronounced seasonality with some revolatilization during summer and gaseous deposition during winter, but overall dry deposition dominates annual mean fluxes. The characteristic patterns of PAHs in the different phases (gas phase, atmospheric passive samplers, bulk deposition, and soil solids) confirm the expected compound-specific distribution pattern and behavior. Since revolatilization fluxes in summer are only minor and wet and dry deposition is ongoing, our results clearly show that the PAH loads in topsoils will continue to increase.

Valproic acid counteracts polycyclic aromatic hydrocarbons (PAHs)-induced tumorigenic effects by regulating the polarization of macrophages

Polycyclic aromatic hydrocarbons (PAHs) are common persistent organic pollutants that are carcinogenic, teratogenic and mutagenic, causing a variety of harm to human health. In this study, we investigated the mechanism of how valproic acid (VPA) interferes with the carcinogenesis of PAHs protect normal tissues via the regulation of macrophages' function. Using the established model of transformed malignant breast cancer by 7,12-dimethylbenz[a]anthracene (DMBA), a representative PAH carcinogen, we discovered VPA induces the polarization of macrophages toward the M1 phenotype in the tumor tissues, facilitates the expression of pro-inflammatory cytokines such as IFN-γ, IL-12 and TNF-α, activates CD8⁺ T cells to secret Granzyme B thus to promote the apoptosis of tumor cells and suppresses the viability of vascular endothelial cells in tissue stroma of tumor. Surprisingly, VPA selectively induces macrophages to polarize towards the M2 phenotype in normal tissues and promotes the expression of anti-inflammatory cytokines such as IL-10 to enhance cell proliferation. Additionally, at the cellular level, VPA can directly regulate the polarization of macrophages to affect the growth of vascular endothelial cells by simulating the living conditions of tumor and normal cells. Collectively, VPA exerts an interventional effect on tumor growth and a protective effect on normal tissues by regulation of selective macrophages' polarization in their microenvironment.

Synergy of the Tropical Earthworm Pontoscolex corethrurus and Oil Palm Bagasse in the Removal of Heavy Crude Oil

The tropical endogeic earthworm Pontoscolex corethrurus, a non-standard species used in ecotoxicity, has been found in crude oil-contaminated habitats. We estimated the removal of total hydrocarbons from heavy crude "Maya" oil on an artificially contaminated soil with a median lethal concentration of P. corethrurus and an addition of oil palm bagasse. P. corethrurus had a high survival rate, and the addition of oil palm bagasse led to a greater growth and an increase in abundance of bacteria and fungi. The activity of P. corethrurus and the nutritional quality of oil palm bagasse had a significant impact on the removal of a larger amount of petroleum hydrocarbons from contaminated soil. We concluded that the endogeic earthworm P. corethrurus and oil palm bagasse acted synergistically to achieve a more effective removal of total petroleum hydrocarbons from soil. These results show the potential for using P. corethrurus to remove, either directly or indirectly, crude oil from soil.

GSDMD-miR-223-NLRP3 axis involved in B(a)P-induced inflammatory injury of alveolar epithelial cells

Benzo(a)pyrene [B(a)P], a ubiquitous environmental pollutant, causes lung inflammatory damage. Pyroptosis，a new inflammation-dependent programmed cell death, happened when pyroptosis-related GSDMD is activated mediated by NLRP3 inflammasome. microRNA-223 (miRNA-223) is involved in inflammatory diseases by regulating NLRP3. However, whether GSDMD regulate NLRP3 inflammasome through miR-223 in B(a)P induced lung inflammatory injury remain unknown. In this study, alveolar epithelial cells (A549) were stimulated with 0, 2, 4, 8 μM B(a)P for 12 h or 24 h. The inflammatory injury and pyroptosis were determined. And the activation of NLRP3 inflammasomes and the level of miRNA-223 were detected. Then, the change of inflammatory injury and activation of NLRP3 inflammasomes in B(a)P-induced A549 cells were detected after inhibiting of GSDMD or miR-223 using siRNA-GSDMD (siGSDMD) or miR-223 inhibitor, respectively. Our results indicated that after B(a)P exposure, TNF-α and IL-6 in the supernatant were increased. Transmission electron microscope (TEM) results showed that A549 cells were obviously swollen and the cell membrane ruptured. Hoechest33342/PI staining showed that pyroptosis occurred. NLRP3, IL-1β, IL-18, GSDMD, GSDMD-N, pro caspase-1 and cleaved caspase-1 were significantly increased. Additionally, after transfecting with siGSDMD in B(a)P-induced A549 cells, the expression level of miR-223 was significantly increased. But IL-6 and TNF-α in the supernatant, the expression of NLRP3, IL-1β, IL-18 and cleaved caspase-1 protein were also decreased. And after inhibiting miR-223 in B(a)P-induced A549 cells, the expression of TNF-α and IL-6 in the supernatant, the protein expression of NLRP3, IL-1β, IL-18 and cleaved caspase-1 were increased. In conclusion, GSDMD may regulate NLRP3 inflammasome through miR-223, which is involved in B(a)P induced inflammatory damage in A549 cells.

Polycyclic aromatic hydrocarbon contamination in soils and sediments: Sustainable approaches for extraction and remediation

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic environmental pollutants that are extremely hydrophobic in nature and resistant to biological degradation. Extraction of PAHs from environmental matrices is the first and most crucial step in PAH quantification. Extraction followed by quantification is essential to understand the extent of contamination prior to the application of remediation approaches. Due to their non-polar structures, PAHs can be adsorbed tightly to the organic matter in soils and sediments, making them more difficult to be extracted. Extraction of PAHs can be achieved by a variety of methods. Techniques such as supercritical and subcritical fluid extraction, microwave-assisted solvent extraction, plant oil-assisted extraction and some microextraction techniques provide faster PAH extraction using less organic solvents, while providing a more environmentally friendly and safer process with minimum matrix interferences. More recently, more environmentally friendly methods for soil and sediment remediation have been explored. This often involves using natural chemicals, such as biosurfactants, to solubilize PAHs in contaminated soils and sediments to allow subsequent microbial degradation. Vermiremediation and microbial enzyme-mediated remediation are emerging approaches, which require further development. The following summarises the existing literature on traditional PAH extraction and bioremediation methods and contrasts them to newer, more environmentally friendly ways.

Bioremediation of Agriculture Soil Contaminated by Organic Pollutants

Pipeline spills and pollution of the environment by crude oil pose a threat to natural resources, especially soil and water. One such incident occurred on 25 September 2018 in the area of Budrovac (Croatia; 46°00′14.6″ N 17°04′16.8″ E) on agricultural land as a pipeline spill. Bioremediation of the contaminated soil was carried out with organic pollutants using an environmentally safe absorbent Spill-Sorb (Canadian Sphagnum Peat Moss) and a mineral fertilizer—nitrogen. The experiment was conducted in the greenhouse of the Faculty of Agriculture, Croatia, during a six-month (October 2018–April 2019) study. Samples of agricultural soils contaminated with total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) were taken after the rupture of the local gas condensate pipeline. The experiment was conducted in five treatments in triplicate: I-control (clean soil); II-100% contaminated soil + organic absorbent + nitrogen; III-100% contaminated soil + organic absorbent; IV-50% clean soil + 50% contaminated soil + organic absorbent + nitrogen; and V-50% clean soil + 50% contaminated soil + organic absorbent. The soil properties studied were pH, organic matter content, carbon and nitrogen content and ratio, and changes in the concentration of potential organic contaminants—TPHs and individual PAHs. The results demonstrated that the mixture of organic absorbent and nitrogen efficiently removed organic pollutants from the contaminated soil within six months. However, the application of Spill-Sorb alone was more effective for the degradation of hydrocarbons. The effectiveness of the absorbent studied was dependent on the concentration of organic pollutants and nitrogen application.

Understanding the Implications of Predicted Function for Assessment of Rapid Bioremediation in a Farmland-Oilfield Mixed Area

Farmland-oilfield mixed areas are fragile ecosystems that require dynamic remediation to counteract the undesirable impact of energy development. Practicable assessment methods are pivotal to a fast and accurate evaluation of the in situ bioremediation process. Petroleum pollutants impose component-dependent effects on autochthonous microbiota before and after remediation. Here, the predicted functional response of soil microbiomes to petroleum pollutants was analyzed in a historically polluted farmland-oilfield mixed area from the perspective of developing a set of feasible biomarkers for immediate post-bioremediation evaluation. An array of microbial, genetic, systematic, and phenotypic biomarkers was proposed. Our results showed that the biomarkers could proxy the stage of the bioremediation multidimensionally. We argue that functional diversity should be considered together with microbial community dynamic to evaluate the restoration status of the microbial communities in petroleum-contaminated farmland-oilfield mixed environments.

Soil conditioners improve rhizodegradation of aged petroleum hydrocarbons and enhance the growth of Lolium multiflorum

Bioremediation and phytoremediation have demonstrated potential for decontamination of petroleum hydrocarbon-impacted soils. The total petroleum hydrocarbons (TPHs) are known to induce phytotoxicity, reduce water retention in soil, associate hydrophobic nature and contaminants' in situ heterogeneous distribution, limit soil nutrient release and reduce soil aeration and compaction. The ageing of TPHs in contaminated soils further hinders the degradation process. Soil amendments can promote plant growth and enhance the TPH removal from contaminated aged soil. In the present experiment, remediation of TPH-contaminated aged soil was performed by Italian ryegrass, with compost (COM, 5%), biochar (BC, 5%) and immobilized microorganisms' technique (IMT). Results revealed that significantly highest hydrocarbon removal (40%) was noted in mixed amendments (MAA) which contained BC + COM + IMT, followed by COM (36%), compared to vegetative control and other treatments. The higher TPH removal in aged soil corresponds with the stimulated rhizospheric effects, as evidenced by higher root biomass (85-159% increase), and bacterial count compared to NA control. Phyto-stimulants actions of biochar and IMT improved seed germination of Italian ryegrass. The compost co-amendment with other treatments showed improvement in plant physiological status. These results suggested that plant growth and TPH removal from aged, contaminated soils using BC, COM and IMT can improve bioremediation efficiency.

Determining the bioavailability of benzo(a)pyrene through standardized desorption extraction in a certified reference contaminated soil

There is a strong need for certified reference materials in the quality assurance of nonionic soil contaminant bioavailability estimations through physicochemical methods. We applied desorption extraction, a method recently standardized as ISO16751, to determine the bioavailable concentration of the most commonly regulated polycyclic aromatic hydrocarbon (PAH), benzo(a)pyrene (BaP), in the reference industrial soil BCR-524 with a certified BaP total concentration of 8.60 mg kg^-1. This concentration represented BaP levels found in many PAH-polluted soils. The method, based on single-point extraction of the analyte desorbed into the aqueous phase by a receiving phase (Tenax or cyclodextrin), was applied ten times. The data fulfilled highly demanding quality criteria based on recovery and repeatability. The bioavailable BaP concentration detected through Tenax extraction, 1.82 mg kg^-1, was comparable to bioavailable concentrations determined in field-contaminated soils and to environmental quality standards based on previously observed total BaP concentrations. There was good agreement (Student's t-test, P ≤ 0.05) with the bioavailable BaP concentration determined by cyclodextrin extraction (1.53 mg kg^-1). The methods were extended to four other certified 4- and 5-ringed PAHs for comparative purposes. We suggest ways of improving of the ISO16751 standard related to further systematic assessment of the Tenax-to-soil ratio and incorporation of mass balances. Furthermore, BCR-524 is suitable for quality-assurance protocols with these methods when used in site-specific risk assessments of PAH-polluted environments.

Mitigation of petroleum-hydrocarbon-contaminated hazardous soils using organic amendments: A review

The term "Total petroleum hydrocarbons" (TPH) is used to describe a complex mixture of petroleum-based hydrocarbons primarily derived from crude oil. Those compounds are considered as persistent organic pollutants in the terrestrial environment. A wide array of organic amendments is increasingly used for the remediation of TPH-contaminated soils. Organic amendments not only supply a source of carbon and nutrients but also add exogenous beneficial microorganisms to enhance the TPH degradation rate, thereby improving the soil health. Two fundamental approaches can be contemplated within the context of remediation of TPH-contaminated soils using organic amendments: (i) enhanced TPH sorption to the exogenous organic matter (immobilization) as it reduces the bioavailability of the contaminants, and (ii) increasing the solubility of the contaminants by supplying desorbing agents (mobilization) for enhancing the subsequent biodegradation. Net immobilization and mobilization of TPH have both been observed following the application of organic amendments to contaminated soils. This review examines the mechanisms for the enhanced remediation of TPH-contaminated soils by organic amendments and discusses the influencing factors in relation to sequestration, bioavailability, and subsequent biodegradation of TPH in soils. The uncertainty of mechanisms for various organic amendments in TPH remediation processes remains a critical area of future research.

Soil indigenous microorganisms weaken the synergy of Massilia sp. WF1 and Phanerochaete chrysosporium in phenanthrene biodegradation

Biodegradation is a promising way to reduce phenanthrene (PHE) in environment. PHE biodegradation by bioaugmentation of axenic and mixed cultures of Massilia sp. WF1 (a highly efficient PHE-degrading bacteria) and Phanerochaete chrysosporium (P. chrysosporium, an extensively researched model fungus in organic pollutant bioremediation) was investigated in aqueous and autoclaved/un-autoclaved soil cultures. In the liquid cultures, the strain WF1 could use PHE (ca. 10 mg L^-1) as the sole carbon source, and the presence of d-fructose (500 mg L^-1) had no obvious effect on its PHE degradation; while the opposite was observed for P. chrysosporium. The bioaugmentation of strain WF1 and P. chrysosporium co-culture showed the highest PHE-degradation efficiency, especially in the aqueous and the autoclaved soil (PHE, ca. 50 mg kg^-1) cultures, indicating a synergistic interaction of the co-culture during PHE dissipation. It was further observed that the indigenous microorganisms (mainly the Gram-positive bacteria) played a dominant role during PHE biodegradation and showed an antagonistic action against the strain WF1-P. chrysosporium co-culture, which weakened the synergistic action of the co-culture in the un-autoclaved soil. Besides, the abundances of PAH-RHDα GP and nidA genes were negatively correlated with residual PHE in the soil. Our findings provide the scientific support for bioremediation of PAHs in environment.

Biochar derived from chicken manure as a green adsorbent for naphthalene removal

In this study, biochar was generated from chicken manure by using a tube furnace under different temperatures (300, 500, and 700 °C), and the treatments were noted as J300, J500, and J700, respectively. In comparison, another type of biochar was prepared under 500 °C with a muffle furnace, and the treatment was noted as JM500. Biochar in treatment group J500 was subsequently modified with HNO₃ and NaOH, and the treatments were noted as J500-HNO₃ and J500-NaOH, respectively. The sorption efficiencies of naphthalene by the above six types of biochar were evaluated. Characteristic results showed that the surface pores of the biochar were improved with the increase of temperature, and biochar under the treatments J300, J500, J700, and JM500 experienced a high speed of adsorption within 1 h after the naphthalene adsorption started. The adsorption capacity of naphthalene increased with the increase of the initial concentration of naphthalene. Treatment J700 exhibited the largest adsorption capacity since its biochar surface pore structure was more fully developed with a crystal structure formed, and its specific surface area was increased by about 20 times compared to the original chicken manure. After biochar modification using HNO₃ and NaOH, the infrared spectrum changed, and the adsorption active sites were increased. The biochar modification by HNO₃ had a high naphthalene adsorption efficiency compared to NaOH. The order of adsorption capacity was as follows: J500 ≈ JM500 < J300 < J500-NaOH < J500-HNO₃ < J700.

Five-Year Enhanced Natural Attenuation of Historically Coal-Tar-Contaminated Soil: Analysis of Polycyclic Aromatic Hydrocarbon and Phenol Contents

The objective of this study was to assess the soil pollution on an industrial wasteland, where coal-tar was processed in the period between 1880 and 1997, and subsequent to assess the decline in the content of phenols and polycyclic aromatic hydrocarbons (PAHs) during enhanced natural attenuation. The soil of the investigated area was formed from a layer of uncompacted fill. Twelve sampling points were established in the investigated area for collecting soil samples. A study conducted in 2015 did not reveal any increase in the content of heavy metals, monoaromatic hydrocarbons (BTEX), and cyanides. However, the content of PAHs and phenols was higher than the content permitted by Polish norms in force until 2016. In the case of PAHs, it was observed for individual compounds and their total contents. Among the various methods, enhanced natural attenuation was chosen for the remediation of investigated area. Repeated analyses of the contents of phenols and PAHs were conducted in 2020. The results of the analyses showed that enhanced natural attenuation has led to efficient degradation of the simplest substances—phenol and naphthalene. The content of these compounds in 2020 was not elevated compared to the standards for industrial wastelands. The three- and four-ring hydrocarbons were degraded at a lower intensity. Based on the mean decrease in content after 5-year enhanced natural attenuation, the compounds can be arranged in the following order: phenols > naphthalene > phenanthrene > fluoranthene > benzo(a)anthracene > chrysene > anthracene.

Influencing factors and health risk assessment of polycyclic aromatic hydrocarbons in groundwater in China

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants. This study investigated the occurrence of 16 PAHs in groundwater of representative regions of China (the cities of Lanzhou, Shijiazhuang, and Golmud and in Du'an County) using a gas chromatograph mass spectrometer. The total concentrations of 16 PAHs (∑PAHs) were in the range 0-29.06 μg/L (average: 594.8 ng/L). Acenaphthylene (Acy) and Naphthalene (Nap) had the highest detected frequency (74.56 %) and highest average concentration (632.7 ng/L), respectively. The average concentration of ∑PAHs in each study area exhibited the following trend: Lanzhou > Golmud > Du'an dry season > Du'an wet season > Shijiazhuang. The dominant PAHs in the study areas comprised mainly 2-4-ring PAHs, i.e., Nap (38.71 %; Shijiazhuang), BaA (40.09 %; Du'an wet season), Ace (16.84 %; Du'an dry season), Nap (43.51 %; Lanzhou), and BaA (57.43 %; Golmud). Overall, the PAHs of 101 samples were derived primarily from combustion and a small number of samples of PAHs originated from petroleum sources. Owing to strong adsorption in the vadose zone, the concentrations of PAHs in Shijiazhuang groundwater were lower than those in the groundwater of Golmud and Du'an. The groundwater in Du'an, Lanzhou and Golmud exhibits potential carcinogenic risk if consumed without further treatment.

Impact of oil contamination on ecological functions of peat soils from West Siberia of Russia

For more than a century, the need for energy has exerted high demand on oil production and led to significant negative impacts on soil and water resources. The aim of our work was to assess such impacts on the ecological functions of oil-contaminated soils in West Siberia of Russia. The total petroleum hydrocarbons (PHC) content in contaminated soils varied between 3.7 and 390 g kg^-1 . Although peat had the ability to absorb some PHC, excess oil migrated in soil both downward and laterally. Catalase activity, soil respiration activity (basal respiration [BR], microbial biomass carbon [Cmic], and specific respiration activity [qCO₂ ]), and Enchytraeus albidus survival and reproduction rates showed significant negative correlations with PHC concentrations, and thus they can be used as guides for establishing acceptable PHC limits in peat soils. Based on the Logit model, the concentration of PHC in peat soil that corresponds to ∼20% reduction on functions (worm reproduction, catalase activity, and basal respiration) is about 40-50 g kg^-1 . The concentrations of PHC that will result in 80% functional reductions (i.e., near-complete loss on functional activities) are worm production (177 g kg^-1 ), catalase activity (123 g kg^-1 ), and basal respiration (311 g kg^-1 ). This study provides quantitative understanding of the ecological impact of PHC contamination on peat soils and thus helps to establish science-based guidelines for the protection of ecological functions and services of peatland soils.

Occurrence and weathering of petroleum hydrocarbons deposited on the shoreline of the North Saskatchewan River from the 2016 Husky oil spill

Following the 16TAN Husky oil spill along the North Saskatchewan River (NSR), the occurrence and natural attenuation of the petroleum hydrocarbons were assessed by analyzing the littoral zone sediments/oil debris collected from July 2016 to October 2017. Husky oil-free, mixed sediment-Husky oil, and Husky oil debris samples were identified for all the collected samples. Shoreline sediments were contaminated by mixed biogenic, pyrogenic and petrogenic inputs prior to the spill. Oil stranded on the shoreline of NSR was moved or buried due to the very dynamic conditions of the shoreline, or cleaned through a series of cleanup activities after the spill. Most normal alkanes were naturally weathered, whereas most of the branched alkanes and all of the saturated petroleum biomarkers remained. Some lighter molecular weight (e.g., 2 to 3-ring) polycyclic aromatic hydrocarbons (PAHs) were lost rapidly after the spill, whereas sulfur containing components, e.g., dibenzothiophenes and benzonaphthothiiophenes, and those having a heavier molecular weight did not change markedly even 15 months post-spill. Similarly, some light hydrocarbons (e.g., <C₁₀) were lost over the first kilometers from the point of entry (POE), while heavier hydrocarbons did not show any major differences away from the POE. Very large inter-site and inter-survey discrepancies were found for samples. Evaporation into the air and dissolution into water, combined with biodegradation, were together or independently the main contributors to the loss of the light molecular hydrocarbons.

Assessing the Spatial Distribution of Soil PAHs and their Relationship with Anthropogenic Activities at a National Scale

Soil polycyclic aromatic hydrocarbon (PAH) pollution is a major concern due to its negative impact on soil quality around the world. In China, accurate data on soil PAHs and information on the relationship with anthropogenic activities are limited. In this study, about 30,800 samples from 1833 soil sample sites were reviewed from 306 published reports to build a soil PAHs database. Based on the data obtained, the results demonstrated that 24.11% of surface soils in China are heavily contaminated. Meanwhile, the concentration of soil PAHs varied, in the order of independent mining and industrial areas (IMIA) > urban areas > suburban areas > rural areas, and the spatial distribution in China demonstrated a descending trend from north to south. Moreover, the characteristic ratio and PCA-MLR (principal component analysis-multiple linear regression) analysis demonstrated that coal combustion and vehicular exhaust emissions were the main sources of soil PAH pollution in China. On the other hand, provincial total Σ₁₆PAHs in surface soil were significantly correlated with the per square kilometer GDP (gross domestic product) of industrial land, the per capita GDP, as well as the production and consumption of energy. These results indicate that anthropogenic factors have greatly affected the levels of soil PAHs in China. This study improves our understanding on the status and sources of soil PAH contamination in China, thereby facilitating the implementation of strategies of prevention, control, and remediation of soils.

Formation and toxicity of polycyclic aromatic hydrocarbons during CaO assisted hydrothermal carbonization of swine manure

The effects of temperature and CaO introduction on polycyclic aromatic hydrocarbons (PAHs) contents, distribution patterns and toxicity of the products from hydrothermal carbonization (HTC) of swine manure (SM) were investigated in this study for the first time. The results indicated that increasing temperature decreased total PAHs content of the hydrochar, while the PAHs toxicity firstly decreased and then increased during HTC of SM. For the aqueous product, the total PAHs content and toxicity gradually decreased with increasing temperature. CaO introduction during HTC of SM significantly suppressed the PAHs formation and promoted the transformation from higher molecular weight PAHs into lower molecular weight PAHs in HTC products, resulting in the remarkably decreased content and toxicity of PAHs. The lowest total PAHs content (1428.57 μg/kg) and TEQ value (21.33 μg/kg) of the hydrochar were obtained by 15% CaO introduction at 200 °C and 180 °C, respectively, and compared to SM, they were decreased by 73.73% and 79.51%, respectively. Moreover, 3-ring PAHs were the predominant PAHs in HTC products regardless of CaO introduction. The present study demonstrated that CaO assisted HTC at temperature lower than 220 °C was effective to reduce the total content and toxicity of PAHs in SM, and the prepared hydrochar was a promising soil amendment in view of the elimination of PAHs toxicity.