A 6-year review status on soil pollution in coal mining areas from Europe.

Coal is an essential component in achieving the goal of fulfilling the energy demands of the world. Nevertheless, the extensive practice of coal mining has resulted in environmental contamination through the release of both organic and inorganic pollutants, including polycyclic aromatic compounds and potentially toxic elements, into various mediums, notably soil. The escalating coal-mining activities across Europe have amplified the concentration of specific elements in the soil. Therefore, a thorough and meticulous assessment of these environmental impacts is imperative to furnish policymakers, industries, and communities with valuable insights, facilitating the formulation and adoption of effective mitigation strategies. Considering the results of studies from 2018 to 2023, this review thoroughly evaluates the current state of soil pollution in the coal mining areas of Europe, focusing on polycyclic aromatic hydrocarbons and potentially toxic elements. By analyzing the acquired data, this study aims to evaluate the levels of contamination by these pollutants in soils. The findings reveal that low molecular weight polycyclic aromatic hydrocarbons dominate the polycyclic aromatic compounds present, while potentially toxic elements including Zn, Pb, Mn, and Cr emerge as major contributors to soil contamination in coal mining areas from Europe.

A review on polycyclic aromatic compounds based chemosensors for toxic ions detection - Present and future perspective.

This comprehensive review delves into the current landscape and future outlook of chemosensors constructed from polycyclic aromatic compounds (PACs) for the detection of toxic ions. PACs, known for their unique molecular properties, have emerged as key building blocks for the development of chemosensors due to their sensitivity, selectivity, and versatility. The review begins by providing an overview of the existing literature on PAC-based chemosensors, detailing their design principles, structural modifications, and mechanisms of ion recognition. The discussion encompasses various toxic ions, including heavy metals, anions, and other environmental pollutants, showcasing the broad applicability of PAC-based chemosensors in diverse analytical contexts. The review also highlights recent advancements in the field, exploring novel strategies and materials for enhancing the performance of PAC-based chemosensors. Furthermore, the review critically evaluates the current challenges and limitations associated with PAC-based chemosensors, offering insights into potential avenues for future research and technological development.

Deep eutectic solvent for the extraction of polycyclic aromatic compounds in fuel, food and environmental samples.

Polycyclic aromatic compounds (PACs) encompass a wide variety of organic analytes that have mutagenic and carcinogenic potentials for human health and are recalcitrant in the environment. Evaluating PACs levels in fuel (e.g., gasoline and diesel), food (e.g., grilled meat, fish, powdered milk, fruits, honey, and coffee) and environmental (e.g., industrial effluents, water, wastewater and marine organisms) samples are critical to determine the risk that these chemicals pose. Deep eutectic solvents (DES) have garnered significant attention in recent years as a green alternative to traditional organic solvents employed in sample preparation. DES are biodegradable, have low toxicities, ease of synthesis, low cost, and a remarkable ability to extract PACs. However, no comprehensive assessment of the use of DESs for extracting PACs from fuel, food and environmental samples has been performed. This review focused on research involving the utilization of DESs to extract PACs in matrices such as PAHs in environmental samples, NSO-HET in fuels, and bisphenols in foods. Chromatographic methods, such as gas chromatography (GC) and high-performance liquid chromatography (HPLC), were also revised, considering the sensibility to quantify these compound types. In addition, the characteristics of DES and advantages and limitations for PACs in the context of green analytical chemistry principles (GAC) and green profile based on metrics provide perspective and directions for future development.

Mountaintop Removal Coal Mining Contaminates Snowpack across a Broad Region.

Mountaintop removal coal mining is a source of downstream pollution. Here, we show that mountaintop removal coal mining also pollutes ecosystems downwind. We sampled regional snowpack near the end of winter along a transect of sites located 3-60 km downwind of coal mining in the Elk River valley of British Columbia, Canada. Vast quantities of polycyclic aromatic compounds (PACs), a toxic class of organic contaminants, are emitted and transported atmospherically far from emission sources. Summed PAC (ΣPAC) snowpack concentrations ranged from 29-94,866 ng/L. Snowpack ΣPAC loads, which account for variable snowpack depth, ranged from <10 µg/m2 at sites >50 km southeast of the mines to >1000 µg/m2 at sites in the Elk River valley near mining operations, with one site >15,000 µg/m2. Outside of the Elk River valley, snowpack ΣPAC loads exhibited a clear spatial pattern decreasing away from the mines. The compositional fingerprint of this PAC pollution matches closely with Elk River valley coal. Beyond our study region, modeling results suggest a depositional footprint extending across western Canada and the northwestern United States. These findings carry important implications for receiving ecosystems and for communities located close to mountaintop removal coal mines exposed to air pollution elevated in PACs.

Ring Rearrangement Reactions of 4-Alkenylisocoumarins and Photophysical Evaluation of Multi-Substituted Anthracene Products.

Herein we report that readily available 4-alkenylisocoumarins can be regarded as potent dienolate equivalents. For example, lactol silyl ethers derived from 4-alkenylisocoumarins were selectively converted to the corresponding benzo-homophthalates through a fluoride-induced ring opening step that was followed by a ring closure through a vinylogous intramolecular aldol condensation. Likewise, nucleophilic activation of 4-alkenylisocoumarins directly yields diversely poly-substituted naphthalenes and anthracenes without formation of any regioisomer. Photophysical evaluation of a set of thus obtained 1,3-di- and 1,3,4-trisubstituted anthracenes reveals their distinct intramolecular charge transfer (ICT) character during light absorption in polar solutions and excimer emission from the solid state when a face-to-face π-stacked molecular assembly is present in the crystal packing.

Genomic, Phylogenetic and Physiological Characterization of the PAH-Degrading Strain Gordonia polyisoprenivorans 135.

The strain Gordonia polyisoprenivorans 135 is able to utilize a wide range of aromatic compounds. The aim of this work was to study the features of genetic organization and biotechnological potential of the strain G. polyisoprenivorans 135 as a degrader of aromatic compounds. The study of the genome of the strain 135 and the pangenome of the G. polyisoprenivorans species revealed that some genes, presumably involved in PAH catabolism, are atypical for Gordonia and belong to the pangenome of Actinobacteria. Analyzing the intergenic regions of strain 135 alongside the "panIGRome" of G. polyisoprenivorans showed that some intergenic regions in strain 135 also differ from those located between the same pairs of genes in related strains. The strain G. polyisoprenivorans 135 in our work utilized naphthalene (degradation degree 39.43%) and grew actively on salicylate. At present, this is the only known strain of G. polyisoprenivorans with experimentally confirmed ability to utilize these compounds.

Tracking the history of polycyclic aromatic compounds in London through a River Thames sediment core and ultrahigh resolution mass spectrometry.

Polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and heteroatom-containing analogues, constitute an important environmental contaminant class. For decades, limited numbers of priority PAHs have been routinely targeted in pollution investigations, however, there is growing awareness for the potential occurrence of thousands of PACs in the environment. In this study, untargeted Fourier transform ion cyclotron resonance mass spectrometry was used for the molecular characterisation of PACs in a sediment core from Chiswick Ait, in the River Thames, London, UK. Using complex mixture analysis approaches, including aromaticity index calculations, the number of molecular PAC components was determined for eight core depths, extending back to the 1930s. A maximum of 1676 molecular compositions representing PACs was detected at the depth corresponding to the 1950s, and a decline in PAC numbers was observed up the core. A case linking the PACs to London's coal consumption history is presented, alongside other possible sources, with some data features indicating pyrogenic origins. The overall core profile trend in PAC components, including compounds with oxygen, sulfur, nitrogen, and chlorine atoms, is shown to broadly correspond to the 16 priority PAH concentration profile trend previously determined for this core. These findings have implications for other industry-impacted environments.

Predicting the Occurrence of Substituted and Unsubstituted, Polycyclic Aromatic Compounds in Coking Wastewater Treatment Plant Effluent using Machine Learning Regression.

Organic contaminants such as polycyclic aromatic compounds (PACs) occurring in industrial effluents can not only persist in wastewater but transform into more toxic and mobile, substituted heterocyclic products during treatment. Thus, predicting the occurrence of PACs and their heterocyclic derivatives (HPACs) in coking wastewater is of utmost importance to reduce the environmental risks in water bodies that receive industrial effluents. Although HPACs can be monitored through sampling and analysis, the characterisation techniques used in their analyses are costly and time-consuming. In this study, we propose 3 distinct kernel-based machine learning (ML) models for predicting PACs including substituted HPACs and alkylated PACs occurring in coking wastewater. By using routinely measured wastewater quality data as input for our models, we predicted the occurrence of 14 HPACs in the final effluent of a coking wastewater treatment plant. Support Vector Machine based regression model (SVR) used for HPAC prediction showed the highest R2 of 0.83. Performance assessment of SVR model showed a mean absolute logarithmic error (MALE) of 0.46 and root mean square error (RMSE) of 0.073 ng/L. Comparatively, K-Nearest Neighbor and Random Forest models showed lower R2 of 0.75 and 0.76 respectively for HPAC prediction. Feature analysis attributed the superior predictability of SVR model likely to its higher weightage (81%) towards dissolved organic carbon and total ammonia as input variables. Both these variables could capture the underlying secondary PAC transformations likely occurring in the treatment plant. Partial dependence plots predicted that ammonia levels higher than 120 mg/L and DOC levels of 50-60 mg/L were likely linked to higher HPACs occurring in the final effluent. This work highlights the capability of kernel-based ML models in capturing nonlinear wastewater chemistry and offers a tool for monitoring trace organic contaminants released in coking effluents.

Migration patterns and health risk assessment of polycyclic aromatic compounds in typical coal fire source.

The Wuda coal fire in Inner Mongolia, China, is a global catastrophic event. It emits a huge volume of organic pollutants, including polycyclic aromatic compounds (PACs), which are widely concerning due to their physiological toxicity and environmental persistence. However, there is no systematic study on the enrichment and migration patterns of PACs emitted from coal fires. Here, we compared samples from coal fire sponges and surrounding soil, and analyzed 47 PACs using GC × GC-TOFMS. Data analysis showed that the average content of 16 polycyclic aromatic hydrocarbons (16PAHs) in the coal fire sponge was 15400.65 ng/g, which is about 4.2 times higher than that in the surrounding soil. Meanwhile, 31 PACs were detected at levels far exceeding those of 16PAHs. The distribution pattern of PACs showed that coal fire sources are more likely to produce and store 16PAHs while surrounding soils are more likely to be enriched with PAH derivatives. The cancer risk assessment revealed a significant cancer risk in both the coal fires and the surrounding soil. The formation mechanism of oxygenated PAHs was also explored, and it was found that coal fires emit 16PAHs and alkylated PAHs, which oxidize to form oxygenated PAHs during migration to surrounding soils. The value of naphthaldehyde/alkylated naphthalene (< 2) can be referenced as characteristic markers of coal fire pollution. This provides a new perspective on the sources of PACs in the current environment.

A validated approach for analysis of heterocyclic aromatic compounds in sediment samples.

The scientific literature is replete with analytical methods for the analysis of homocyclic aromatic compounds especially polycyclic aromatic hydrocarbons and their alkylated analogs. However, there is a paucity of methods for the analysis of nitrogen-, sulfur- and oxygen-containing polycyclic aromatic compounds (PACs). The lack of commercially available analytical standards, the presence of many structural derivatives and isomers and lack of certified reference materials all contribute to the inherent challenges in measuring these compounds. Gas chromatography coupled with a tandem mass spectrometer was used to develop two multiple reaction monitoring methods to detect and quantify fifty-three non-halogenated and halogenated hetero-polycyclic aromatic compounds (HPACs). Because of their greater polarity, strongly non-polar solvents typically employed to extract homocyclic PACs from sediment samples did not yield acceptable recoveries of our target analytes. By adding ethyl acetate to dichloromethane (50:50), recoveries of our target analytes using accelerated solvent extraction increased markedly. The performance characteristics of the validated method including accuracy [> than 67% for 46 (out of 53) analytes], inter- and intra-day precision [<30% for all analytes, (expressed as relative standard deviation)], limits of detection (0.1 to 2.3 ng/g) and quantitation (1.5 to 7.6 ng/g) imply that the method is fit for its intended purpose. A sediment sample from a known contaminated site in Canada was analyzed for both homo- and hetero-PACs. Measured concentrations of Σ27HPAC (7.3 µg/g, dry weight) were significantly smaller (p<0.05) than Σ16PAHs (80.9 µg/g, dry weight) and Σ30Alkylated-PAHs (14.2 µg/g, dry weight). These results suggest that the developed method is an effective and efficient approach for the targeted analysis of HPACs and their halogenated derivatives in sediment samples.

Air-soil cycling of oxygenated, nitrated and parent polycyclic aromatic hydrocarbons in source and receptor areas.

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, OPAHs and NPAHs, are semivolatile air pollutants which are distributed and cycling regionally. Subsequent to atmospheric deposition to and accumulation in soils they may re-volatilise, a secondary source which is understudied. We studied the direction of air-soil mass exchange fluxes of 12 OPAHs, 17 NPAHs, 25 PAHs and one alkylated PAH in two rural environments being influenced by the pollutant concentrations in soil and air, by season, and by land cover. The OPAHs and NPAHs in samples of topsoil, of ambient air particulate and gas phases and in the gas-phase equilibrated with soil were analysed by GC-APCI-MS/MS. The pollutants soil burdens show a pronounced seasonality, a winter maximum for NPAHs and PAHs and a summer maximum for OPAHs. One order of magnitude more OPAH and parent PAH are found stored in forest soil than in nearby grassland soil. Among a number of 3-4 ring PAHs, the OPAHs benzanthrone and 6H-benzo(c,d)pyren-6-one, and the NPAHs 1- and 2-nitronaphthalene, 9-nitrophenanthrene and 7-nitrobenz(a)anthracene are found to re-volatilise from soils at a rural background site in central Europe in summer. At a receptor site in northern Europe, net deposition of polycyclic aromatic compounds (PACs) prevails and re-volatilisation occurs only sporadic. Re-volatilisation of a number of PACs, including strong mutagens, from soils in summer and even in winter indicates that long-range atmospheric transport of primary PAC emissions from central Europe to receptor areas might be enhanced by secondary emissions from soils.

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

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

Historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, Swedish west coast as reflected in a high-resolution sediment record and compared to the Environmental Quality Standards (EQS).

We present the historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, a relatively unexploited area, on the Swedish west coast. PACs encompass various compounds, including PAHs, alkyl-PAHs, nitro-PAHs, and oxy-PAHs. These compounds, have environmental implications due to their harmful properties. Using a high-resolution sediment record, PAC variations including standard PAHs, nitro-PAHs and oxy-PAHs were investigated over the last approximately 170 years, comparing them with other European records. The sediment record reveals a significant increase in PAC levels during the 1940s-1950s, followed by peaks in the 1960s and 1970s, and a subsequent decrease in the 1980s. These trends align with industrial growth and evolving stronger environmental regulations in the region. The highest recorded concentration of PACs (1950-1970) reached levels comparable to present-day polluted urban environments. The study also compared PAH levels with EQS values. Results indicated that PAH levels exceeded EQS standards, potentially posing risks to sediment-dwelling organisms.

Biphenylene-containing polycyclic conjugated compounds.

There has been a growing emphasis on the synthesis of polycyclic conjugated compounds, driven by their distinct structural characteristics that make them valuable candidates for use in cutting-edge technologies. In particular, acenes, a subgroup of polycyclic aromatic compounds, are sought-after synthetic targets due to their remarkable optoelectronic properties which stem from their π-conjugation and planar structure. Despite all these promising characteristics, acenes exhibit significant stability problems when their conjugation enhances. Various approaches have been developed to address this stability concern. Among these strategies, one involves the incorporation of the biphenylene unit into acene frameworks, limiting the electron delocalization through the antiaromatic four-membered ring. This review gives a brief overview of the methods used in the synthesis of biphenylenes and summarizes the recent studies on biphenylene-containing polycyclic conjugated compounds, elucidating their synthesis, and distinct optoelectronic properties.