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

Redox-switchable microemulsions with efficient phase separation and surfactant recycling

HYPOTHESIS

Switchable microemulsions (MEs) are those capable of adaptively responding to the action of internal or external stimuli. For redox-switchable MEs to obtain high-efficiency phase separation and surfactant recycling, it may be one of the keys to adequately turn off the interfacial activity of surfactants and reduce the solubility of the closed surfactants in the oil phase.

EXPERIMENTS

Monophasic MEs consisting 11-butylselanyl-undecyl sulfate sodium (C4SeC11SO4Na), n-butanol, n-octane, and water were fabricated using the pseudo-ternary phase diagram method. Their structural features and droplets size were characterized by conductivity, dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM), respectively. The redox response of MEs was studied using a combination of visual observations and DLS, cryo-TEM, nuclear magnetic resonance (NMR) and thin-layer tomography. The efficient recycling of C4SeC11SO4Na from a well-emulsified eluent is conceptually demonstrated.

FINDINGS

The reversible transition between C4SeC11SO4Na and C4SeOC11SO4Na is achieved under the alternating action of H2O2 and N2H4, by which C4SeC11SO4Na-based monophasic MEs are able to efficiently demulsify and regenerate, respectively, regardless of their type. After H2O2-induced demulsification of the MEs, C4SeOC11SO4Na can be efficiently recycled with the water phase. We hope that such a redox-switching method may benefit some technological applications. For example, it offers exciting possibilities for simultaneous recycling C4SeC11SO4Na and removal of oil from a well-emulsified eluent. Around 97.1 ± 0.3 % of C4SeC11SO4Na could be recycled over five cycles with no apparent loss. After a simple and conventional treatment with anion-exchange resin and active carbon, the total organic carbon and chemical oxygen demand of the waste water were 17.4 ± 2.8 and 26.2 ± 1.4 mg/L, respectively.

Benzo(b)fluoranthene and benzo(k)fluoranthene removal by microalgae in the presence of triazine herbicides: Matrix solid-phase dispersion and solid-phase extraction (MSPD/SPE) for HPLC-UV analysis of the different culture components

Over the last decade, human activities in the industrial and agricultural sectors have significantly increased the concentration of persistent and harmful pollutants in aquatic ecosystems. The use of microorganisms is a green strategy for the bio-removal of certain contaminants. However, other pollutants in the same ecosystems can reduce their degrading activity and even affect their survival. Therefore, this study aimed to evaluate the efficiency of benzo(b)fluoranthene (BbF) and benzo(k)fluoranthene (BkF) removal by Selenastrum capricornutum in the presence of triazine herbicides, compounds mainly used in broadleaf weeds. The interest of this work focused on identifying in which of the microalgal components the degrading activity is best evidenced and affected. For this purpose, the use of solid-phase extraction (SPE) and matrix solid-phase dispersion (MSPD) extraction procedures and HPLC-UV analysis allowed the BbF and BkF trace quantification in biomass, liquid medium, and cell lysate separately from cultures exposed to these polycyclic aromatic hydrocarbons (PAHs) alone or with herbicides. The recovery percentages were between 78 and 94 %, good linearity (r2 ≈ 0.99), precision values measured as RSD < 15 %, and limits of detection (LOQs) at levels of ng mL-1 and ng mg-1 were obtained. The individual PAH amounts measured in the components of microalgae cultures show similar removal kinetics (removal percentages: 82-89 %). Likewise, the analysis demonstrated that the removal of PAHs is not affected in the presence of triazine herbicides (atrazine and cyanazine) and with similar removal percentages (79-86 %) compared to those cultures exposed to individual PAHs (74-83 %). These results support the possible real-world applications of PAH removal by extracts from S. capricornutum in aquatic environments contaminated with PAHs and near agriculture areas where triazine herbicides are used.

PAHs contamination in ports: Status, sources and risks

Polycyclic aromatic hydrocarbons (PAHs) constitute important organic contaminants that have been degrading coastal ecosystems over the years. Evaluating PAH status in port ecosystems aligns with societal goals of maintaining clean habitats and sustainability. This comprehensive review systematically analyzed 123 articles, exploring the global distribution, sources, and ecological risks linked to PAH contamination in ports, focusing on water, sediment, and biota. The mean concentrations of 16 PAHs in water, sediment, and biota across worldwide ports were 175.63 ± 178.37 ng/L, 1592.65 ± 1836.5 μg/kg, and 268.47 ± 235.84 μg/kg, respectively. In line with PAH emissions and use in Asia, Asian ports had the highest PAH concentrations for water and biota, while African ports had the highest PAH concentrations for sediment. The temporal trend in PAH accumulation in sediments globally suggests stability. However, PAH concentrations in water and biota of global ports exhibit increasing trends, signaling aggravating PAH contamination within port aquatic ecosystems. Some ports exhibited elevated PAH levels, particularly in sediments with 4.5 %, 9.5 %, and 21 % of the ports categorized as very poor, poor, and moderate quality. Some PAH isomers exceeded guidelines, including the carcinogenic Benzo(a)pyrene (BaP). Coal, biomass, and petroleum combustion were major sources for PAHs. The structure of ports significantly influences the concentrations of PAHs. PAH concentrations in sediments of semi-enclosed ports were 3.5 times higher than those in open ports, while PAH concentrations in water and biota of semi-enclosed ports were lower than those in open ports. Finally, risk analyses conducted through Monte Carlo simulation indicated moderate to high risks to aquatic species, with probabilities of 74.8 % in water and 34.4 % in sediments of ports worldwide. This review underscores the imperative to delve deeper into the accumulation of PAHs and similar pollutants in ports for effective management and environmental protection.

Co-occurrence of polycyclic aromatic hydrocarbons and heavy metals in various environmental matrices of a chronic petroleum polluted region in Iran; Pollution characterization, and assessment of ecological and human health risks

Oil spills from pipeline accidents can result in long-lasting health effect in the people living in a ‎polluted region‎. In this study, the level of the 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs‎) and heavy metals (HMs) have been ‎analyzed in environmental matrices of a region with frequent oil ‎pipeline accidents in Iran‎.‎ The results showed that the mean ‎concentration of ΣPAHs and ΣHMs decreased from the upstream to the downstream and also the levels were ‎higher in the wet season than those in the dry season. The average concentration of HMs in sediments was higher than that in other ‎environments. The 3-ring and 4-ring PAHs were dominant in all of the studied matrices with the average values of 32.61 % and 45.85 %, respectively. The ecological risks of PAHs and HMs were medium and high in all matrices, respectively. In wet season, the total cancer risk (TCR) related to PAHs in agricultural soil was greater than 10-4, whereas it's very close to the threshold for HMs in water. This study offers a reference for assessing the long-term impact of oil spills in contaminated environmental matrices. The results are crucial for developing effective strategies to mitigate oil pollution ‎impacts and protect environmental and public health.

Degradation of pyrene by Xanthobacteraceae bacterium strain S3 isolated from the rhizosphere sediment of Vallisneria natans: active conditions, metabolite identification, and proposed pathways

Polycyclic aromatic hydrocarbons (PAHs) were typical environmental contaminants that accumulated continuously in sediment. Microbial degradation is the main way of PAH degradation in the natural environment. Therefore, expanding the available pool of microbial resources and investigating the molecular degrading mechanisms of PAHs are critical to the efficient control of PAH-polluted sites. Here, a strain (identified as Xanthobacteraceae bacterium) with the ability to degrade pyrene was screened from the rhizosphere sediment of Vallisneria natans. Response surface analysis showed that the strain could degrade pyrene at pH 5-7, NaCl addition 0-1.5%, and temperature 25-40 °C, and the maximum pyrene degradation (~ 95.4%) was obtained under the optimum conditions (pH 7.0, temperature 28.5 °C, and NaCl-free addition) after 72 h. Also, it was observed that the effect of temperature on the degradation ratio was the most significant. Furthermore, eighteen metabolites were identified by mass spectrometry, among which (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid, 7-(carboxymethyl)-8-formyl-1-naphthyl acetic acid, phthalic acid, naphthalene-1,2-diol, and phenol were the main metabolites. And the degradation pathway of pyrene was proposed, suggesting that pyrene undergoes initial ortho-cleavage under the catalysis of metapyrocatechase to form (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid. Subsequently, this intermediate was progressively oxidized and degraded to phthalic acid or phenol, which could enter the tricarboxylic acid cycle. Furthermore, the pyrene biodegradation by the strain followed the first-order kinetic model and the degradation rate changed from fast to slow, with the rate remaining mostly slow in the later stages. The slow biodegradation rate was probably caused by a significant amount of phenol accumulation in the initial stage of degradation, which resulted in a decrease in bacterial activity or death.

Photocatalytic degradation of fluoranthene in soil suspension by TiO2/α-FeOOH with enhanced charge transfer capacity

Polycyclic aromatic hydrocarbons (PAHs) in soil are potentially harmful to human health. However, the use of photocatalysis technology to treat soil contaminated with PAHs remains challenging. Therefore, TiO2/α-FeOOH composite photocatalyst has been synthesized by hydrothermal method and sol-gel method and applied to photocatalytic degradation of fluoranthene in soil. The morphology, elements, crystal structure, optical properties, electrochemical characteristics, and photocatalytic activity of TiO2/α-FeOOH have been characterized. Results showed that TiO2 is tightly fixed on the surface of α-FeOOH, and TiO2/α-FeOOH had higher photocatalytic activity on photocatalytic degradation of fluoranthene in soil under simulated sunlight. The degradation efficiency of TiO2/α-FeOOH is 3.0 and 4.8 times higher than that of TiO2 and α-FeOOH, respectively. This is attributed to enhanced photocatalytic ability by enhancing the transfer capacity of electrons and holes and broadening the spectrum absorption range. The highest degradation efficiency was achieved when the pH of the soil is neutral, the ratio of water/soil is 10:1, and the dosage of catalyst is 50 mg/g. In addition, it was proved that •O2-, h+, and 1O2 are the main active substances in the photocatalysis of TiO2/α-FeOOH. The possible mechanism of a Z-type electron transfer structure was also proposed. The degradation products of fluoranthene were detected, and the degradation pathway was deduced.

Microstructure-dependent CO2-responsive microemulsions for deep-cleaning of oil-contaminated soils

CO2-responsive microemulsion (ME) is considered a promising candidate for deep-cleaning and oil recovery from oil-contaminated soils. Understanding the responsive nature of different microstructures (i.e., oil-in-water (O/W), bicontinuous (B.C.) and water-in-oil (W/O)) is essential for unlocking the potential and mechanisms of CO2-responsive emulsions in complex multiphase systems and providing comprehensive guidance for remediation of oil-contaminated soils. Herein, the responsiveness of microstructures of ME to CO2 trigger was investigated using experimental designs and coarse-grained molecular dynamic simulations. MEs were formed for the first time by a weakly associated pseudo-Gemini surfactant of indigenous organic acids (naphthenic acids, NAs are a class of natural surface-active molecules in crude oil) and tetraethylenepentamine (TEPA) through fine tuning of co-solvent of dodecyl benzene sulfonic acid (DBSA) and butanol. The O/W ME exhibited an optimal CO2-responsive character due to easier proton migration in the continuous aqueous phase and more pronounced dependence of configuration on deprotonated NA ions. Conversely, the ME with W/O microstructure exhibited a weak to none responsive characteristic, most likely attributed to its high viscosity and strong oil-NA interactions. The O/W ME also showed superior cleaning efficiency and oil recovery from oil-contaminated soils. The results from this study provide insights for the design of CO2-responsive MEs with desired performance and guidance for choosing the favorable operating conditions in various industrial applications, such as oily solid waste treatment, enhanced oil recovery (EOR), and pipeline transportation. The insights from this work allow more efficient and tailored design of switchable MEs for manufacturing advanced responsive materials in various industrial sectors and formulation of household products.

Development of a Multifaceted Perspective for Systematic Analysis, Assessment, and Performance for Environmental Standards of Contaminated Sites

Contaminated soil and groundwater can pose significant risks to human health and ecological environments, making the remediation of contaminated sites a pressing and sustained challenge. It is significant to identify key performance indicators and advance environmental management standards of contaminated sites. The traditional study currently focuses on the inflexible collection of related files and displays configurable limitations regarding integrated assessment and in-depth analysis of published standards. In addition, there is a relative lack of research focusing on the analysis of different types of standard documents. Herein, we introduce a cross-systematic retrospective and review for the development of standards of the contaminated sites, including the comprehensive framework, multifaceted analysis, and improved suggestion of soil and groundwater standards related to the environment. The classification and structural characteristics of different types of files are systematically analyzed of over 300 national, trade, local, and group standards for the contaminated sites. It exhibits that trade standards are the main types and testing methods are the important format within numerical considerations of soil standards. The guide standard serves as a crucial component in environmental management for investigating, assessing, and remediating of contaminated sites. Future improvement plans and development directions are proposed for advancing robust technical support for effective soil contamination prevention and control. This multidimensional analysis and the accompanying suggestions can provide improved guidance for Chinese environmental management of contaminated sites and sparkle the application of standards in a wide range of countries.

Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Marine pollutant Phenanthrene (PHE) exposure causes immunosuppression of hemocytes in crustacean species, Scylla paramamosain

Phenanthrene (PHE), a representative polycyclic aromatic hydrocarbons (PAHs), is widely found in aquatic environments, which exhibits high toxicity to aquatic organisms and has a substantial impact on overall health. In order to investigate the immunosuppressive effects of PHE exposure on marine crustacean species, the Scylla paramamosain was exposure to different concentrations of PHE, which was 0 μg/L (control group), 0.7 μg/L, 7 μg/L, or 70 μg/L PHE with 35 individuals in every group, respectively. The results showed that the color of hemocytes gradually deepened with increasing PHE concentration, and the total hemocyte count (THC) was activated and increased after PHE exposure analyzed by Flow cytometry. Meanwhile, compared with the control group, cryostat sections of hepatopancreas showed cell infiltration, cell steatosis, eosinophilic masses and vacuolization in PHE groups. The superoxide dismutase (SOD) activity was decreased immensely in PHE exposure groups, meanwhile, the acid phosphatase (ACP) activity and glutathione (GSH) activities were increased after PHE exposure compared with control group. Moreover, the expression profile of Crustin, TLR, MCM7, JAK, caspase, Moyosin and P53 were up-regulated significantly after 7th day PHE exposure in all treatment groups by Q-PCR. Those data illustrated that PHE exposure could inhibit the immune function of mud crab by causing hepatopancreas damage, induce the activity of antioxidant enzymes and the expression of immune genes. These data provide a scientific basis for evaluating the impact of PAH pollution on marine organisms.

Occurrence, distribution and risk assessment of polycyclic aromatic hydrocarbons in soils around main water source areas of Beijing, China

Polycyclic aromatic hydrocarbons (PAHs) in urban environments have been globally concerned due to their significant health impacts on residents. However, little is known about potential risks of PAHs from centralized water source areas. In the present study, 326 soils samples from the main water source areas of Beijing were collected and the occurrence, source appointment, and risks of PAHs were systematically investigated based on the monitoring results from high-performance liquid chromatography (HPLC). The total PAHs (∑16 PAHs) concentrations ranged from 5.70 to 1512 ng/g with median value of 44.2 ng/g, in which 4-ring and 5-ring groups were the major components. PAHs concentrations in the cultivated land were significantly higher than other areas, which could reflect significant impact of soil organic matter and total nitrogen contents on the spatial variations of PAHs. Further source identifications through positive matrix factorization model (PMF) revealed that biomass (22.5%), coal (21.4%), gasoline (17.6%) and diesel (16.4%) combustion were dominant sources of soil PAHs in the study area. Moreover, the risk assessment indicated that total ecological and health risk of PAHs were negligible, but individual PAH, including pyrene and benzo(b)fluoranthene, should be concerned due to their potential risks in several monitored stations located in the secondary protection area of four reservoirs. Our study provided new insights into environmental risks of soils in main water source areas from PAHs and could be helpful for organic micropollutant controlling and drinking water safety in rapidly urbanizing cities.

Insights into relationships between polycyclic aromatic hydrocarbon concentration, bacterial communities and organic matter composition in coal gangue site

Coal mining usually brought polycyclic aromatic hydrocarbons (PAHs) contamination. Relationships between the concentration of PAHs, bacterial communities and soil environmental factors were important for bioremediation of PAHs in soil. Total 4 kinds of soil samples with different concentrations of PAHs were selected from 7 typical coal gangue（CG） sites in Huainan, Anhui Province. The relationships between microorganisms, dissolved organic matter (DOM) composition and PAHs concentration were systematically analyzed in this work. Total 11 kinds of PAHs were enriched in the soil surface layer. That was attributed to the strong binding of soil organic matter (SOM) to PAHs. PAHs contamination reduced the diversity of soil microbial. The abundance of PAHs-degrading genera such as Arthrobacter decreased with the increasing concentration of PAHs. Mycobacterium increased with the increasing concentration of PAHs in all samples. The microbial activities decreased with increasing concentration of PAHs. The increasing contents of LWM-PAHs and DOM were beneficial to improve the activities of soil microbial. The increasing DOM aromaticity was beneficial to improve the bioavailability of PAHs according to the correlation analysis between PAHs content and DOM structural parameters. The obtained results provide a basis for better understanding the contamination characteristics and microbial communities of coal gangue PAH-contaminated sites.

Propylene glycol-mixed steam enhanced extraction for an efficient and sustainable remediation of PAHs-contaminated soil

An innovative thermal desorption method, propylene glycol (PG)-mixed steam enhanced extraction, is proposed for a highly efficient remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. It is found that injecting PG-mixed steam into soil column could obtain > 99% removal efficiencies of PAHs either for the pyrene-spiked soil, or for the contaminated field soil with high-molecular-weight PAHs. PG is a safe and low-cost dihydric alcohol with a boiling point higher than water. When the PG-mixed steam penetrated the contaminated soil, the PG vapor preferentially condensed to form a hot liquid with concentrated PG (e.g., from 30 wt% PG in gas phase to 90 wt% PG in the liquid phase), which would significantly solubilize the PAHs and enhance their desorption from soils. The results also revealed that the effluents derived from the PG-mixed steam could be purified by removing the desorbed PAHs using a simple coagulation treatment, and the recovered PG solution could be reused. The plant assay using wheat seeds showed that the remediated soil had a good regreening potential. Our results demonstrate that PG-mixed steam injection is a promising thermal desorption method for an efficient and sustainable remediation of PAHs-contaminated soil.

Rice genotypes and root-associated niches shifted bacterial community in response to pollution of di-(2-ethylhexyl) phthalate (DEHP) for promoting DEHP removal

Organic pollutants influenced root-associated bacterial community. However, the response variation of root-associated bacterial community among different rice genotypes exposed to phthalates (PAEs) and their removal mechanism remains unknown. Here, bacterial community and PAE-degrading genes in root-associated niches were analyzed between low (Fengyousimiao) and high (Hhang) PAE-accumulating rice cultivars exposed to di-(2-ethylhexyl) phthalate (DEHP). DEHP dissipation percentages in rhizosphere of Hhang were significantly higher than those of Fengyousimiao. The bacterial community diversities (including Chao1 and Shannon index) significantly decreased along bulk soil - rhizosphere - rhizoplane - endosphere. The bacterial community structures were shaped mainly by root-associated niches, DEHP pollution and rice genotypes, with significant differences in rhizosphere and rhizoplane between Fengyousimiao and Hhang. Rhizosphere enriched more PAE-degrading bacteria than in bulk soil, and exhibited significantly higher expression of PAE-degrading genes (hydrolase 65, phtab, phtC, pcaF and pcaI) than in bulk soil. Furthermore, rhizosphere of Hhang demonstrated significantly stronger bacterial functions related to xenobiotics biodegradation and higher expression of PAE-degrading genes than those of Fengyousimiao, leading to significantly higher DEHP dissipation percentages in rhizosphere of Hhang. The findings demonstrate that Hhang shaped specific root-associated bacterial community with higher abundances of PAE-degrading bacteria and genes than Fengyousimiao to promote DEHP degradation.

Electrokinetic remediation leads to translocation of dissolved organic matter/nutrients and oxidation of aromatics and polysaccharides

Dissolved organic matter (DOM) in the sediment matrix affects contaminant remediation through consumption of oxidants and binding with contaminants. Yet the change in DOM during remediation processes, particularly during electrokinetic remediation (EKR), remains under-investigated. In this work, we elucidated the fate of sediment DOM in EKR using multiple spectroscopic tools under abiotic and biotic conditions. We found that EKR led to significant electromigration of the alkaline-extractable DOM (AEOM) toward the anode, followed by transformation of the aromatics and mineralization of the polysaccharides. The AEOM remaining in the cathode (largely polysaccharides) was resistant to reductive transformation. Limited difference was noted between abiotic and biotic conditions, indicating the dominance of electrochemical processes when relatively high voltages were applied (1-2 V/cm). The water-extractable organic matter (WEOM), in contrast, showed an increase at both electrodes, which was likely attributable to pH-driven dissociations of humic substances and amino acid-type constituents at the cathode and the anode, respectively. Nitrogen migrated with the AEOM toward the anode, but phosphorus remained immobilized. Understanding the redistribution and transformation of DOM could inform studies on contaminant degradation, carbon and nutrient availability, and sediment structural changes in EKR.

Nationwide distribution of polycyclic aromatic hydrocarbons in soil of China and the association with bacterial community

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has raised great environmental concerns. However, the information on national wide distribution of PAHs in soil as well as their effect on soil bacterial community are limited. In this study, 16 PAHs were measured in 94 soil samples collected across China. The total concentration of 16 PAHs (∑PAHs) in soil ranged from 74.0 to 17,657 ng/g (dry weight basis), with a median value of 200 ng/g. Pyrene was the major soil PAH, with a median concentration of 71.3 ng/g. Soil samples from Northeast China had a higher median concentration of ∑PAHs (1,961 ng/g) than those from other regions. Petroleum emission and wood/grass/coal combustion were potential sources for soil PAHs based on diagnostic ratios and positive matrix factors analysis. A nonnegligible ecological risk (hazard quotients > 1) was found in over 20% of soil samples analyzed and the highest median total HQs value (8.53) was found in soils from Northeast China. The effect of PAHs on bacterial abundance, α-diversity, and β-diversity was limited in the soils surveyed. Nevertheless, the relative abundance of some members in genera Gaiella, Nocardioides, and Clostridium was significantly correlated with the concentrations of some PAHs. Especially, the bacterium Gaiella Occulta showed potential in indicating soil contamination by PAH, which is worth further exploration.

Optimization and Comparison of Microwave-Assisted Extraction, Supercritical Fluid Extraction, and Eucalyptus Oil-Assisted Extraction of Polycyclic Aromatic Hydrocarbons from Soil and Sediment

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic compounds of major concern that mainly accumulate in soils and sediments, and their extraction from environmental matrices remains a crucial step when determining the extent of contamination in soils and sediments. The objective of the present study was to compare the extraction of PAHs (phenanthrene, pyrene, chrysene, and benzo[a]pyrene) from spiked soil and sediment using supercritical fluid extraction (SFE) with ethanol as the modifier, microwave-assisted extraction (MAE), and eucalyptus oil-assisted extraction (EuAE). Recoveries of PAHs were comparable between the three methods, and >80% of applied pyrene, chrysene and benzo[a]pyrene were recovered. The most efficient method of extracting PAHs from naturally incurred soils with different levels of contamination was SFE. A longer extraction time was required for the EuAE method compared with SFE and MAE under optimized conditions. However, EuAE required lower extraction temperatures (15-20 °C) compared with SFE (80 °C) and MAE (110-120 °C), and consumed less solvent than SFE and MAE. Compared with hexane/acetone used in MAE, the use of ethanol in SFE and eucalyptus oil in EuAE can be considered as more sustainable approaches to efficiently extract PAHs from spiked/naturally contaminated soils and sediments. And, although less efficient for matrices containing higher carbon content, EuAE offered a cheap, low-tech approach to extracting PAHs. Environ Toxicol Chem 2023;42:982-994. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Revealing the key species for pyrene degradation in Vallisneria natans rhizosphere sediment via triple chamber rhizome-box experiments

To identify key species associated with pyrene degradation in Vallisneria natans (V.natans) rhizosphere sediment, this work investigated the temporal and spatial changes in the rhizosphere microbial community and the relationship between the changes and the pyrene degradation process through a three-compartment rhizome-box experiment under pyrene stress. The degradation kinetics of pyrene showed that the order of degradation rate was rhizosphere > near-rhizosphere > non-rhizosphere. The difference in the pyrene degradation behavior in the sediments corresponded to the change in the proportions of dominant phyla (Firmicutes and Proteobacteria) and genera (g_Massilia f_Comamonadaceae, g_Sphingomonas). The symbiosis networks and hierarchical clustering analysis indicated that the more important phyla related to the pyrene degradation in the rhizosphere was Proteobacteria, while g_Sphigomonas, f_Comamonadaceae, and especially g_Massilia were the core genera. Among them, f_Comamonadaceae was the genus most affected by rhizosphere effects. These findings strengthened our understanding of the PAHs-degradation microorganisms in V.natans rhizosphere and are of great significance for enhancing phytoremediation on PAHs-contaminated sediment.

Endophytic, extremophilic and entomophilic fungi strains biodegrade anthracene showing potential for bioremediation

Anthropogenic activities have been increasing Polycyclic Aromatic Hydrocarbons (PAHs) release, promoting an urgent need for decontamination methods. Therefore, anthracene biodegradation by endophytic, extremophilic, and entomophilic fungi was studied. Moreover, a salting-out extraction methodology with the renewable solvent ethanol and the innocuous salt K₂HPO₄ was employed. Nine of the ten employed strains biodegraded anthracene in liquid medium (19-56% biodegradation) after 14 days at 30 °C, 130 rpm, and 100 mg L^-1. The most efficient strain Didymellaceae sp. LaBioMMi 155, an entomophilic strain, was employed for optimized biodegradation, aiming at a better understanding of how factors like pollutant initial concentration, pH, and temperature affected this process. Biodegradation reached 90 ± 11% at 22 °C, pH 9.0, and 50 mg L^-1. Futhermore, 8 different PAHs were biodegraded and metabolites were identified. Then, experiments with anthracene in soil ex situ were performed and bioaugmentation with Didymellaceae sp. LaBioMMi 155 presented better results than natural attenuation by the native microbiome and biostimulation by the addition of liquid nutrient medium into soil. Therefore, an expanded knowledge about PAHs biodegradation processes was achieved with emphasis to the action of Didymellaceae sp. LaBioMMi 155, which can be further employed for in situ biodegradation (after strain security test), or for enzyme identification and isolation aiming at oxygenases with optimal activity under alkaline conditions.

Oxygenated polycyclic aromatic hydrocarbons in food: toxicity, occurrence and potential sources

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are polycyclic aromatic hydrocarbons (PAHs) functionalized with at least one carbonyl group and are generally thought to be more toxic than PAHs. In this review, the physical-chemical properties, toxicity, occurrence, and potential sources of OPAHs in food were comprehensively discussed. The toxicities of 1,2-naphthoquinone, 1,4-naphthoquinone, 6H-benzo[cd]pyren-6-one, benzo[a]anthracene-7,12-quinone and 9,10-phenanthrenequinone were prominent among the OPAHs. Both 1,4-naphthoquinone and 1,2-naphthoquinone exhibited strong genotoxicity, cytotoxicity, and developmental toxicity. 6H-benzo[cd]pyren-6-one and benzo[a]anthracene-7,12-quinone showed high genotoxicity and cardiovascular toxicity. Although 9,10-phenanthrenequinone showed no genotoxicity, it exhibited almost the strongest cytotoxicity. For the majority of foods, the concentrations of OPAHs and PAHs were on the same order of magnitude. OPAHs tend to be positively correlated with the corresponding PAH concentrations in oil and fried food, while for barbequed food and seafood, no obvious correlation was found. In addition, 9-fluorenone, 9,10-anthraquinone, benzanthrone and 1,2-acenaphthenequinone had high abundance in food. Environmental pollution, food composition, storage conditions, heating methods, and other treatments influence the accumulation of OPAHs in food. Furthermore, oxygen and water played an important role in the transformation from PAHs to OPAHs. In short, this review guides the evaluation and further reduction of OPAH-related health risks in food.

A review on lignin pyrolysis: pyrolytic behavior, mechanism, and relevant upgrading for improving process efficiency

Lignin is a promising alternative to traditional fossil resources for producing biofuels due to its aromaticity and renewability. Pyrolysis is an efficient technology to convert lignin to valuable chemicals, which is beneficial for improving lignin valorization. In this review, pyrolytic behaviors of various lignin were included, as well as the pyrolytic mechanism consisting of initial, primary, and charring stages were also introduced. Several parallel reactions, such as demethoxylation, demethylation, decarboxylation, and decarbonylation of lignin side chains to form light gases, major lignin structure decomposition to generate phenolic compounds, and polymerization of active lignin intermediates to yield char, can be observed through the whole pyrolysis process. Several parameters, such as pyrolytic temperature, time, lignin type, and functional groups (hydroxyl, methoxy), were also investigated to figure out their effects on lignin pyrolysis. On the other hand, zeolite-driven lignin catalytic pyrolysis and lignin co-pyrolysis with other hydrogen-rich co-feedings were also introduced for improving process efficiency to produce more aromatic hydrocarbons (AHs). During the pyrolysis process, phenolic compounds and/or AHs can be produced, showing promising applications in biochemical intermediates and biofuel additives. Finally, some challenges and future perspectives for lignin pyrolysis have been discussed.

Development of a new methodology for multifaceted assessment, analysis, and characterization of soil contamination

It is important to identify key performance and core progress features of soil contamination management practices. Traditional research currently focuses on numerical statistics of contaminated sites but exhibits structural limitations regarding cross-assessment and in-depth analysis of published findings. Herein, we report a multidimensional perspective to assess the environmental management performance of soil contamination via systematic and historical development of construction land risk control and remediation lists (RCRLs). The considered contaminated sites are mainly concentrated in Northern China, Yangtze River Delta, Pearl River Delta, and Sichuan-Chongqing regions. Monthly historical overviews indicate that most lists are updated 4-5 times within 32 months. Direct chemical-related industrial production results in the largest number of contaminated sites. Arsenic and lead are the most common heavy metals of concern in soil contamination. The fiscal revenue index exhibits the best positive performance in terms of the number of contaminated sites. By employing the site number, update frequency, and published contents of different calculation proportions, ten types of integrated assessment indicators (IAIs) are established to evaluate the environmental achievements in various provincial regions in regard to soil contamination protection. This multifaceted strategy can provide advanced guidance for Chinese environmental management and expand the application of soil pollution risk control and remediation in a wide range of countries.

Potential Toxicity Risk Assessment and Priority Control Strategy for PAHs Metabolism and Transformation Behaviors in the Environment

In this study, 16 PAHs were selected as the priority control pollutants to summarize their environmental metabolism and transformation processes, including photolysis, plant degradation, bacterial degradation, fungal degradation, microalgae degradation, and human metabolic transformation. Meanwhile, a total of 473 PAHs by-products generated during their transformation and degradation in different environmental media were considered. Then, a comprehensive system was established for evaluating the PAHs by-products' neurotoxicity, immunotoxicity, phytotoxicity, developmental toxicity, genotoxicity, carcinogenicity, and endocrine-disrupting effect through molecular docking, molecular dynamics simulation, 3D-QSAR model, TOPKAT method, and VEGA platform. Finally, the potential environmental risk (phytotoxicity) and human health risks (neurotoxicity, immunotoxicity, genotoxicity, carcinogenicity, developmental toxicity, and endocrine-disrupting toxicity) during PAHs metabolism and transformation were comprehensively evaluated. Among the 473 PAH's metabolized and transformed products, all PAHs by-products excluding ACY, CHR, and DahA had higher neurotoxicity, 152 PAHs by-products had higher immunotoxicity, and 222 PAHs by-products had higher phytotoxicity than their precursors during biological metabolism and environmental transformation. Based on the TOPKAT model, 152 PAH by-products possessed potential developmental toxicity, and 138 PAH by-products had higher genotoxicity than their precursors. VEGA predicted that 247 kinds of PAH derivatives had carcinogenic activity, and only the natural transformation products of ACY did not have carcinogenicity. In addition to ACY, 15 PAHs produced 123 endocrine-disrupting substances during metabolism and transformation. Finally, the potential environmental and human health risks of PAHs metabolism and transformation products were evaluated using metabolic and transformation pathway probability and degree of toxic risk as indicators. Accordingly, the priority control strategy for PAHs was constructed based on the risk entropy method by screening the priority control pathways. This paper assesses the potential human health and environmental risks of PAHs in different environmental media with the help of models and toxicological modules for the toxicity prediction of PAHs by-products, and thus designs a risk priority control evaluation system for PAHs.

Poly(divinylbenzene) as a fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons from river water

Porous polydivinylbenzene microspheres with high specific surface area were prepared by distillation-precipitation polymerization, and were used as the coating material in headspace solid phase microextraction for extracting polycyclic aromatic hydrocarbons. Compared with the other reported sorbents, PDVB exhibits lower cost and higher extraction efficiency, and the enrichment factors can reach 5963-16 720.

Porous Hexagonal Boron Nitride as Solid-Phase Microextraction Coating Material for Extraction and Preconcentration of Polycyclic Aromatic Hydrocarbons from Soil Sample

Sample pretreatment plays important role in the analysis and detection of trace pollutants in complex matrices, such as environmental and biological samples. The adsorption materials of sample pretreatment receive considerable attention, which has a significant effect on the sensitivity and selectivity of the analytical method. In this work, the porous hexagonal boron nitride (h-BN) was utilized as a coating material of solid-phase microextraction (SPME) to extract and preconcentrate polycyclic aromatic hydrocarbons (PAHs) prior to separation and detection with GC-FID. Attributed to the multiple interactions including hydrophobicity, hydrogen bonding and strong π–π interaction, the h-BN coating showed excellent extraction performance for PAHs. Under the optimal conditions, the method showed the linear relationship in the range of 0.1–50 ng mL⁻¹ for acenaphthene, 0.05–50 ng mL⁻¹ for pyrene, and 0.02–50 ng mL⁻¹ for fluorene, phenanthrene and anthracene with a correlation coefficient (R²) not lower than 0.9910. The enrichment factors were achieved between 1526 and 4398 for PAHs with h-BN as SPME fiber coating. The detection limits were obtained in the range of 0.004–0.033 ng mL⁻¹, which corresponds to 0.08–0.66 ng g⁻¹ for soil. The method was successfully applied to analysis of real soil samples. The recoveries were determined between 78.0 and 120.0% for two soil samples. The results showed that h-BN material provided a promising alternative in sample pretreatment and analysis.