Fraction Of Polycyclic Aromatic Hydrocarbons Research Articles

Magnetic activated carbon (MAC) mitigates contaminant bioavailability in farm pond sediment and dietary risks in aquaculture products

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) are among the contaminants of concern in aquaculture ponds due to their frequent detection and high bioaccumulation in aquatic products and hence high dietary risks to human beings. In this study, magnetic activated carbon (MAC) was added as a stabilization and removal adsorbent to native pond sediment with known contamination of HMs and PAHs to reduce the tissue residues and dietary risks of HMs and PAHs in a model aquaculture species (Venerupis philippinarum) in the course of a 28-day bioaccumulation experiment. Meanwhile, passive sampling techniques based on diffusive gradient in thin films (DGT) and polydimethylsiloxane (PDMS) were applied to sense the bioavailable fraction of HMs and PAHs in sediment during the stabilization process. The results showed that 3% dosage of MAC to sediment achieved the most cost-effective stabilization for HMs and PAHs. A remarkable decrease was observed with the tissue residues of HMs and PAHs in V. philippinarum (28–47% for HMs and ~76% for ∑PAHs), which was quantitatively linked to the decline in their bioavailable concentrations in sediment pore water (31–46% for HMs and ~76% for ∑PAHs). Consequently, the target hazard quotients (THQs) posed by HMs and incremental lifetime cancer risks (ILCRs) by PAHs in V. philippinarum were reduced by 38% and 46%, respectively. Along with the magnetic recovery of ~70% MAC from the sediment, HMs (4.8–13%) and PAHs (2–60%) can be effectively removed. We further established a multi-domain equilibrium sorption model that was able to predict the optimal amendment of MAC for quantitative mitigation of bioavailable PAHs in sediment pore water within a certain range of MAC dosage. Future studies are warranted to explore the applicability domain of MAC for in situ remediation in aquaculture ponds to ensure the quality of farming organisms or to serve other purposes in aquatic systems.

Modelling the spinning dust emission from LDN 1780

ABSTRACT We study the anomalous microwave emission (AME) in the Lynds Dark Nebula (LDN) 1780 on two angular scales. With publicly available data at an angular resolution of 1°, we studied the spectral energy distribution of the cloud in the 0.408–2997 GHz frequency range. The cloud presents a significant (>20σ) amount of AME, making it one of the clearest examples of AME on 1 ° scales, and its spectrum can be well fitted with a spinning dust (SD) model. We also find at these angular scales that the location of the peak of the emission at lower frequencies (23–70 GHz) differs from the location at the higher frequencies (90–3000 GHz) maps. In addition to the analysis on 1° angular scales, we present data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at 31 GHz with an angular resolution of 2 arcmin, in order to study the origin of the AME in LDN 1780. We studied morphological correlations between the CARMA map and different infrared tracers of dust emission. We found that the best correlation is with the 70- μm template, which traces warm dust (T ∼ 50 K). Finally, we study the difference in radio emissivity between two locations within the cloud. We measured a factor of ≈6 difference in 31-GHz emissivity. We show that this variation can be explained, using the SD model, by a variation on the dust grain size distribution across the cloud, particularly changing the fraction of polycyclic aromatic hydrocarbon for a fixed total amount of carbon.

Magnetic solid-phase extraction as a novel method for the prediction of the bioaccessibility of polycyclic aromatic hydrocarbons

Chemical methods used to predict the bioaccessibility of hydrophobic organic compounds (HOCs) still need further development and improvement. In this work, magnetic solid-phase extraction (MSPE) based on poly(β-cyclodextrin)-coated magnetic polydopamine (Fe3O4@PDA@PCD) was first introduced to assess the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soils. Due to its good hydrophilicity and submicrometer scale, Fe3O4@PDA@PCD displayed a higher extraction rate for PAHs in an aqueous solution (equilibrium time < 5 min) than Tenax resin, which had an equilibrium time longer than 30 min. The merits of Fe3O4@PDA@PCD are beneficial to accelerate the desorption of PAHs from soil, especially for high molecular weight PAHs, in which the amounts extracted by Fe3O4@PDA@PCD were 1.2–2.8 times higher than those extracted by Tenax resin. The desorption kinetics data were well fitted with a two- or three-fraction model. The fitting results indicated that the MSPE method can be used to predict the bioaccessible fractions of PAHs. By comparing the prediction results obtained from the MSPE method with bioassays using earthworms, a significant linear correlation (R2 = 0.98) with a slope statistically close to 1 was obtained. These results suggested that the MSPE method can act as a simple and efficient method to measure the bioaccessibility of PAHs in soil.

Rhizosphere-enhanced biosurfactant action on slowly desorbing PAHs in contaminated soil

We studied how sunflower plants affect rhamnolipid biosurfactant mobilization of slowly desorbing fractions of polycyclic aromatic hydrocarbons (PAHs) in soil from a creosote-contaminated site. Desorption kinetics of 13 individual PAHs revealed that the soil contained initially up to 50% slowly desorbing fractions. A rhamnolipid biosurfactant was applied to the soil at the completion of the sunflower cycle (75 days in greenhouse conditions). After this period, the PAHs that remained in the soil were mainly present in a slowly desorbing form as a result of the efficient biodegradation of fast-desorbing PAHs by native microbial populations. The rhamnolipid enhanced the bioavailable fraction of the remaining PAHs by up to 30%, as evidenced by a standardized desorption extraction with Tenax, but the enhancement occurred with only planted soils. The enhanced bioavailability did not decrease residual PAH concentrations under greenhouse conditions, possibly due to ecophysiological limitations in the biodegradation process that were independent of the bioavailability. However, biodegradation was enhanced during slurry treatment of greenhouse planted soils that received the biosurfactant. The addition of rhamnolipids caused a dramatic shift in the soil bacterial community structure, which was magnified in the presence of sunflower plants. The stimulated groups were identified as fast-growing and catabolically versatile bacteria. This new rhizosphere microbial biomass possibly interacted with the biosurfactant to facilitate intra-aggregate diffusion of PAHs, thus enhancing the kinetics of slow desorption. Our results show that the usually limited biosurfactant efficiency with contaminated field soils can be significantly enhanced by integrating the sunflower ontogenetic cycle into the bioremediation design.

DNS-driven analysis of the Flamelet/Progress Variable model assumptions on soot inception, growth, and oxidation in turbulent flames

Modeling suites for Large-Eddy Simulations of soot evolution in turbulent flames include a number of submodels describing the chemistry of soot precursors, particle dynamics, heterogeneous soot chemistry, turbulent mixing, and combustion. To understand the reasons for model failure and to enhance the overall model performance, it is necessary to identify and subsequently improve model components with a leading order effect on the overall error. In this work, errors in soot predictions associated with flamelet-based combustion models are isolated and quantified in a combined a-priori and partial a-posteriori analysis using large-scale Direct Numerical Simulation (DNS) data of a sooting turbulent jet diffusion flame. Gas-phase quantities entering the calculation of the soot source terms and hence coupling the combustion model to the soot model are analyzed in the DNS first. The performance of a Flamelet/Progress Variable model with respect to these quantities is then analyzed a-priori for two DNS cases employing a mixture-averaged transport model and unity Lewis numbers. Then, the soot evolution along Lagrangian trajectories extracted from the DNS is re-computed using rate coefficients directly taken from the DNS and from the flamelet table. In the context of this partial a-posteriori analysis, flamelet-induced errors are also compared to errors induced by the chemical soot model. The soot surface growth and oxidation rate coefficients are reasonably well predicted by the flamelet library. Considerably larger errors in the model-predicted soot mass originate from the tabulated quantities entering the calculation of PAH-based soot growth rates. However, these errors can be reduced to a few percent if the rate is appropriately scaled with the mass fraction of polycyclic aromatic hydrocarbons (PAH). However, this requires the solution of a transport equation for the PAH mass fraction, and modeling the source term in this equation is shown to be challenging. Overall, the largest uncertainties can be attributed to the chemical mechanism for PAH formation and the model for the PAH source term.

Potential sources, influencing factors, and health risks of polycyclic aromatic hydrocarbons (PAHs) in the surface soil of urban parks in Beijing, China

Urban parks are an important part of the urban ecological environment. The environmental quality of parks is related to human health. To evaluate sources of polycyclic aromatic hydrocarbons (PAHs) in soils of urban parks and their possible health risks, soil samples from 122 parks in Beijing, China, were collected and analyzed. The total content of 16 PAHs between 0.066 and 6.867 mg/kg. Four-ring PAHs were predominant, followed by 5-ring PAHs, while the fraction of 2-ring PAHs was the lowest. The dominant PAHs sources were found to be coal combustion and oil fuels such as gasoline and diesel. A conditional inference tree (CIT) was used to identify the key influencing factors for PAHs. Traffic emissions was the most important factor, followed by coal consumption, as well as the history and location of the park. Incremental lifetime cancer risk (ILCR) for urban park soil in Beijing were low under normal conditions. The soil PAHs exposure pathway risk for both children and adults decreased in the following order: ingestion > dermal contact > inhalation. The risk from soil in parks to children’s health is slightly higher than that of adults, although the health risk due to exposure to PAHs was not extraordinary. Ecosystem risk was negligible.

Environmental aspects of petroleum storage in above ground tank

Oil pollution is a severing global environmental problem causing a number of adverse negative impacts on human health air ecosystem and eventually the natural income that is why soil, water, air pollution with petroleum hydrocarbons have become the focus of increasing public and research concern petroleum hydrocarbon contaminants in the air environment are caused by human activities when harmful or excessive quantities of substances are introduced into Earth’s atmosphere. Sources of air pollution include gases such as carbon monoxide, sulfur dioxide, hydrogen sulfide, methane, the aliphatic and polycyclic aromatic hydrocarbons (PAH’s) fractions of petroleum are readily evolved to air during refinery and choosing the wrong storage tanks also leak to the soil change the chemical composition of spilled toxicity and biological impacts of the oil and add great difficulties to the identification of the residual spilled oil in the impacted environment and economic cost of air pollution in illness, health care costs, lost productivity so coordination between humans to conserves natural resources for future generation.

Comparative Study on the Formation and Oxidation of Polycyclic Aromatic Hydrocarbons in the Combustion of Four Butanol Isomers

The formation and oxidation of polycyclic aromatic hydrocarbons (PAHs) precursors during the combustion of n-, sec-, iso- and tert-butanol are computationally investigated at an equivalence ratio of 1.5, an initial pressure of 1.0 atm and a temperature range from 800 to 2000 K in a perfectly stirred reactor. The results indicate that branched chain structure led to an increase in the mole fraction of PAHs. Tert-butanol has the greatest ability in forming PAHs, it can be attributed to the advantage in the β-C–H bonds number. The rate of production analysis reveals that for the butanol isomers with the hydroxyl (OH) group attached to a terminal carbon (n- and iso-butanol), the role of OH radical in the oxidation process of PAHs is enhanced. Compared to the other three butanol isomers, a significant increase in the contribution ratios of C5 and C9 pathways to the formation of PAHs for tert-butanol is observed.

The distribution distance of polycyclic aromatic hydrocarbons in the tundra zone under the impact of thermal power plant

Being widely distributed in the tundra zone and highly sensible to temporal or spatial changes in composition of polycyclic aromatic hydrocarbons (PAHs) in ecosystems, Pleurozium schreberi Brid. can serve a pollution indicator of tundra biocenoses with polyarenes. The purpose of the present study is estimating the PAH distribution distance in the tundra zone under the impact of thermal power plant (TPP). The study was conducted in the Bolshezemelskaya tundra area of the Vorkuta region (Komi Republic, Russia). The surface accumulation and total content of PAHs in Pleurozium schreberi and organic horizon of tundra surfacegley soils (Stagnic Cambisols) at the background site and sites removed from the TPP at 0.5; 1; 1.5; 3; 5 and 12 km were studied. The PAH content in Pleurozium schreberi under the impact of TPP changes with distance not linearly. The maximum accumulation was noted at 3 km distance, then the content of PAHs decreased and reached a background level of 12 km from the source. The high molecular weight structures seemed to be transported at distance of no more than 3 km and fell down to the moss surface. The light structures could fly further. This fact responded for concentration of heavy and light structures on particles with different diameter. The moss surface at the background and polluted sites did not contain naphthalene. The total polyarene capacity on the moss surface is relatively the same for the background and polluted sites. At 3 km site, there was a sharp increase in the mass fraction of surface PAH by a factor of 3 due to an increase in the mass fraction of 4-5 - nuclear polyarenes. Being contaminated, the moss activates the bioaccumulation processes of PAHs and so transports polyarenes from its surface to inner organs. The exclusion is a site at a distance of 3 km where the proportion of surface accumulation increased with maximum pollution, i.e., PAH ingress into moss decreased. Determined that the dead part of Pleurozium schreberi or the whole plant is to be used for true identification of polyarenes. The changes in polyarene content in organic soil horizons are the same as in Pleurozium schreberi . By the obtained data, PAHs in tundra can move at large distances. The background-like PAH values are estimated for the site as 12 km from the pollution source for Pleurozium schreberi . The background-like PAH values for organic soil horizons are not estimated. The obtained results agree with the cluster analysis data.

Polydopamine-coated polyethylene sieve plate as an efficient and convenient adsorption sink for the bioaccessibility prediction of PAHs in soils

Bioaccessibility measurements of polycyclic aromatic hydrocarbons (PAHs) in soils are significant for exposure risk assessment. The current physicochemical methods require tedious operation processes, underestimate the actual risks, or are unsuitable for high organic content soils. In this work, an efficient and convenient method based on polydopamine-coated polyethylene sieve plate (PDA@PESP) and hydroxypropyl-β-cyclodextrin (HPCD) was developed to predict the bioaccessibility of PAHs in multi-type soils. The PDA@PESP can be prepared via in situ self-polymerization, allowing to extract PAHs from HPCD solution quantitatively and rapidly. When applied to evaluate the bioaccessibility with PDA@PESP as an adsorption sink and HPCD as a diffusive carrier, the proposed method can significantly improve the extractable fraction of PAHs compared to single HPCD extraction in particular for high organic carbon content soil and high-ring PAHs. The desorption kinetics data indicated that the method can predict the bioaccessible fraction of PAHs. In addition, the method predicted a satisfactory accumulation into earthworms (Eisenia fetida) with a slope statistically approximated to 1. A highly significant linear regression (R2 = 0.95) was also found between the proposed method and Tenax desorption in historically contaminated soils, demonstrating that the method is an efficient and convenient approach for the bioaccessibility prediction of PAHs in soils.

Polycyclic Aromatic Hydrocarbons in Peat Mounds of the Permafrost Zone

The accumulation of polycyclic aromatic hydrocarbons (PAHs) in the profiles of permafrost-affected peat mounds is related to certain groups of plant residues produced in the Atlantic climatic optimum of the Holocene. Both “heavy” (benzo[ghi]perylene, dibenz[a,h]anthracene, and benzo[b]fluoranthene) and “light” (pyrene and naphthalene) PAHs predominate in them. The polyarenes preserved in the permafrost horizons are not subjected to transformation in contrast to the polyarenes in the active layer. Dynamic freeze–thaw processes at the boundary between seasonally thawed and permanently frozen layers result in considerable transformation of plant remains, humic substances, and nonspecific organic compounds with the accumulation of 5–6-nuclear PAH structures. The composition of PAHs in peatlands and a significant increase in the weight fraction of PAHs at the boundary between seasonally thawed and permafrost layers may serve as indicators of permafrost response to climate changes in high latitudes.

Atmospheric carbonation reduces bioaccessibility of PAHs in industrially contaminated soil

Sorptive Bioaccessibility Extraction (SBE) was used to monitor changes in accessibility of polycyclic aromatic hydrocarbons (PAHs) during storage of historically contaminated alkaline soil (Σ US EPA 16 + 2 further PAHs: 2452 ± 69 mg kg−1, n = 3). While total concentrations of PAHs were rather stable during storage for 561 days at 4 °C, PAH accessibility declined by 95% due to atmospheric carbonation. The formation of carbonates was evidenced by an increase of inorganic soil carbon and by carbonate coatings on black soil particles (SEM-EDX) that could be dissolved by providing neutral to acidic soil conditions. Subjecting soil (252 days of storage) to biodegradation at pH 7 resulted in a degraded fraction of PAHs equivalent to the accessible PAH fraction of soil as received (PAHs with log Kow <5). The present study addresses important interactions and relationships between carbonation of soil, aging of PAHs in soil and related changes in PAH accessibility. A main finding was the reversibility of this retention mechanism, a changing environment (e.g. reduction of pH below 8) can result in a rise of accessible PAHs and consequently in an increase of exposure and associated risk.

Simultaneous determination of 16 polycyclic aromatic hydrocarbons in groundwater by GC-FID after solid-phase extraction

Groundwater contamination by polycyclic aromatic hydrocarbons (PAH) may pose a risk to human health, as these compounds are considered to be highly toxic, carcinogenic and/or mutagenic and bioaccumulative. The aim of this study was to evaluate and determine PAH levels in groundwater samples collected from tubular wells in a city of northern Brazil by gas chromatography with flame ionization detector (GC-FID) used by the population for consumption. Sample pre-treatment using solid-phase extraction cartridges was performed in order to promote an enrichment of the PAH fraction of interest and to remove interferences from the matrix to further determine PAH in samples by GC-FID. The results obtained showed that all groundwater samples studied presented PAH levels lower than maximum values allowed by MS 2914/2011 and CONAMA 396/2008. The developed procedure is characterized by low limits of detection and quantification, equal to 0.024–0.113 µg L−1 and 0.079–0.378 μg L−1, respectively, good linearity (r2 > 0.99). The recoveries obtained for 16 PAH by the addition and recovery method ranged from 85.4 to 105.7% with good precision (RSD < 5.0%). The results of this study showed that the method developed is fast, accurate and robust with high efficiency for identification and determination of 16 PAH in groundwater samples.

Inhalation cancer risk from PM10 in the metropolitan subway stations in Korea

IntroductionAlthough subways have many advantages as a transport system, passengers may be exposed to indoor air pollution. In such cases, the dominant risk factors are associated with particulate matter (PM) bound metals and polycyclic aromatic hydrocarbons (PAHs). In this study, inhalation cancer risks (ICR) were assessed at Seoul metro subway stations (SMS), South Korea, in 2014–2015. MethodsThe mass fractions of PAHs and metals in PM10 were calculated from the previous studies. The PM10 exposure and mass deposition in various sections of the human respiratory tract (HRT) was calculated using mass deposition technique. In addition, ICR via exposure of PM10 in HRT and incremental lifetime cancer risk (ILCR) were estimated for the teen and adult groups of commuters at SMS. Moreover, ICR levels have been compared with incremental lifetime cancer risk (ILCR) levels for SMS commuters. ResultsThe PM10 pollution levels at SMS were found within the acceptable range for the subway platforms in Korean (150 μg/m3). In addition, the maximum amounts of total deposition (TD) and head deposition (HD) in HRT were estimated for the adult group. Hence, tracheobronchial (TB) and alveoli (A) depositions were calculated height for the teen. For the adult and teen groups, ICR(TD) level found significant (>1 × 10−6) for Cr and PAHs. But, among both age groups, significant values of total ICR(TBD + AD) were estimated for the teen (1.40 × 10−06). In addition, the ICR(TD) and ILCR have estimated the same order of inhalation cancer risk for both groups. ConclusionIn the SMS, cancer risk levels were estimated in the acceptable range (1 × 10−06 - 1 × 10−05) of life carcinogenic risk for the commuters, provided by the World Health Organization (WHO). Furthermore, Cr and Ni were identified as significant contributors to inhalation cancer risks with 58% and 39% of total risk level, respectively for teen and adult.

Reduced bioavailability and ecological risks of polycyclic aromatic hydrocarbons in Yangshan port of East China Sea: Remediation effectiveness in the transition from construction to operation

To assess the remediation effectiveness of ecological restoration in the transition period from construction to operation of Yangshan Port, the largest deepwater port of East China Sea, we employed equilibrium passive sampling and partitioning theory to assess the changing bioavailability and flux of polycyclic aromatic hydrocarbons (PAHs) in relation to bioaccumulation and ecological risks in marine organisms. Due to the ecological restoration efforts, both the bulk and bioavailable concentrations of PAHs in sediment and surface seawater samples decreased dramatically after the port entered the operation phase, as compared with those reported during the last construction phase. PAH concentrations in the marine organisms also showed a dramatic decline, and corresponded to the change in the freely dissolved fractions of PAHs in sediment/surface water according to their thermodynamic potential for bioaccumulation. While trophic magnification of ΣPAHs was observed in the pelagic communities, concentrations of PAHs in benthic species were relatively consistent across multiple trophic levels, and were generally higher than those in pelagic species. The differing bioaccumulation between benthic and pelagic species may be related to the habitat-specific bioavailability of PAHs and the prey-predator relations among different species. The incremental lifetime cancer risks (ILCR) of PAHs in marine organisms also dropped by nearly three orders of magnitude, and were lower than the guideline (1 × 10−6) proposed by the U.S. EPA, except for several species at higher trophic levels. Overall, our study highlights an integrated use of passive sampling and equilibrium partitioning theory as a robust tool that can be applied to assess the effectiveness of ecological remediation in the port environment with quantitative, mechanistic insights from bioavailability to bioaccumulation.

Contribution of soil erosion to PAHs in surface water in China

In China, the total annual atmospheric emission of 16 polycyclic aromatic hydrocarbons (PAHs) reach up to approximate 100 thousand tons, part of which is preserved in soils. In this study, the contribution of soil erosion to PAHs in surface water nationwide was quantified. The results indicate that a major portion of the annual PAHs emission is lost from soils via rainfall erosivity and subsequently transported to the ocean. The national annual flux of PAHs from soil to surface water by the natural physical forces of water measures up to ~70 thousand tons, which accounts for ~62% of the annual emission of PAHs with 19% entering the sea directly. In general, both the soil erosion intensity and flux of PAHs for the regions located in the Southeast of China are over those in the Northwest of China, with the regions being divided into two different parts by the famous geographic “Hu Huanyong line”, reflecting the intensive impact of human activities on environmental degradation. Comparative analysis suggested that there must be a big fraction of PAHs lost during transmission due to the river sedimentation and lake dispersion. This study closes a major gap in the national budget of PAHs and provides critical information in the context of regional environment risk assessment.

Studies of Star-forming Complexes in the Galaxies NGC 628, NGC 2976, and NGC 3351

We analyze parameters of the interstellar matter emission in star-forming complexes in the high metallicity galaxies NGC~628, NGC~2976, and NGC~3351, which have different morphological types. The relation between H$\alpha$ emission and emission in CO and HI lines is considered along with the relation between H$\alpha$ emission and dust emission in the infrared range (IR). The fluxes and surface brightnesses in the UV and IR correlate well with H$\alpha$ emission. The HI emission also correlates well with H$\alpha$, while the correlation between the CO and H$\alpha$ emission is much less prominent. The ratio of the fluxes at 8 and 24 $\mu$m decreases with increasing H$\alpha$ flux. This may be due to changes in the properties of the dust ensemble (a decrease in the mass fraction of polycyclic aromatic hydrocarbons) or to changes in excitation conditions. Analysis of the kinematics of the CO lines shows that the CO flux grows with increasing velocity scatter $\Delta V$ when $\Delta V\lesssim70$~km/s. Preliminary evidence for the existence of star-forming complexes with higher values of $\Delta V$ is presented, and the increase in the velocity scatter is accompanied by a decrease in the CO line luminosity of the complex.

Accumulation of polycyclic aromatic hydrocarbons in snow cover near fuel and energy enterprises of the Vorkuta city

The paper deals with the composition of polycyclic aromatic hydrocarbons (PAHs) in snow cover near the city of Vorkuta (Komi Republic, Russia) in the impact zone of the fuel and energy complex. It includes the results on background aero technogenic pollution levels of Vorkuta and its suburbs for subsequent ecological monitoring and on precipitation areas of different PAH fractions within the impact zones of combined heat-and-power plants, the central water boiler plant, and the territory of Vorkuta. “Light” (easily mobile) PAHs are present at almost any test site and attain extreme values in the impact zones of heat-and-power plant 1, heat-and-power plant 2, the central water boiler plant, and the territory of Vorkuta. They are transported at large distances because of high volatility. In addition, light PAHs are transported with air aerosols as they get adsorbed on fine dust particles. “Heavy” PAHs are present on the territory of the city and in the impact zones of the both energy-and-power plants with local pollution extremes from heat-and-power plant 2 at distances of 0.5, 3.0, 11.2 km but are not transported outside 11.2 km. There are interlinks between accumulation of PAHs and other organic and inorganic pollutants. Concerning analyses of PAHs from snow cover, there exist certain territorial groups which allow for understanding pollution sources (fuel and energy complex, auto transport, coal mining). Indicating ratios of PAHs in snow cover of Vorkuta evidence their pyrogenic genesis.

Gas–particle partition and spatial characteristics of polycyclic aromatic hydrocarbons in ambient air of a prototype coking plant

This study investigated the gas–particle partition and spatial characteristics of polycyclic aromatic hydrocarbons (PAHs) in the ambient air of a prototype coking plant. High-volume samplers with glass fiber filters (GFFs) and polyurethane foams (PUFs) were used to collect PAHs in both gaseous and particulate phases. The EPA's 16 priority-controlled PAHs were measured using gas chromatography equipped with a mass-selective detector (GC-MS). The total PAH concentrations ranged from 1.32 μg m−3 to 9.41 μg m−3, with an average of 4.20 μg m−3. PAH abundance at the various sites of the coking plant was determined to be in the following order: coke side > machine side > leeward site; the lowest values were at the reference site and factory boundary. The medium-molecular-weight PAHs had the highest fraction at the coke side, whereas the low-molecular-weight PAHs were predominant at other sampling sites. Considerable amount of chrysene was detected at the coke side, fluorene at the machine side, acenaphthene at the leeward site (240 m downwind of the coke oven), and naphthalene at the other three sites. The gaseous fractions of PAHs at the six sampling sites ranged from 46.3% to 85.8% of the total PAHs in the gas–particle systems; and gaseous PAHs were predominant in the ambient air of the coking plant—except for the coke side, where the PAHs were dominantly partitioned to the particles. In addition, the particulate benzo(a)pyrene equivalence (BaPeq) fraction was high in the coking plant air. The slope (mr) values ranged from −0.59 to −0.39 in the plant, indicating that the absorption mechanism, rather than the adsorption mechanism, dominated the gas–particle partitioning. The intercept (br) values carry the information on the gaseous–particulate phase distribution of semivolatile organic compounds when the mr values are similar. The organic matter fraction in particles, particulate phase fraction of PAHs, and toxicity of particulate matter were found to increase with an increase in br values at similar mr values. The predominant mechanism was absorption for dibenz(a,h)anthracene, benzo(ghi)perylene, and indeno(1,2,3-cd)pyrene, but adsorption for benzo(b)fluoranthene, benzo(a)pyrene, and benzo(k)fluoranthene at the coke and machine sides. By contrast, for most high-molecular-weight PAHs, absorption into the organic matter was the predominant mechanism at other sites. The gas–particle partitioning mechanism of individual PAHs was closely related to the distance from the coke oven, rather than the orientation to the oven. These results may be of great importance in understanding the pollutant process and atmospheric transport of PAHs and may provide guidance to decision makers regarding air pollution control.

Star formation and polycyclic aromatic hydrocarbons in ELAIS N1 galaxies as seen by AKARI

Abstract We have examined the relationship between star formation and polycyclic aromatic hydrocarbons (PAHs) in a variety of galaxies. PAHs are excited by the ultraviolet photons of young stars, but they are disassociated by strong UV radiation in starbursts. Therefore their emission (which is in the wavelength range covered by AKARI) can be used as a star formation tracer in main sequence galaxies. We selected our targets in the ELAIS N1 field with AKARI detections, matched them with the Herschel Point Source Catalog, and collected other publicly available photometric data. Their spectral energy distributions (SEDs) were fitted, and several parameters of the galaxies were estimated, e.g., star formation rate (SFR), stellar mass, and the fraction of PAHs compared to dust mass (qPAH), and we examined the relationships between these parameters. The final sample consisted of 48 galaxies, with redshifts from 0.04 to 2.36. The estimated qPAH values were lower on average than typical values in the literature. This could be due to various reasons, such as low metallicity, or ongoing active galactic nucleus or starburst activity. Of our sample, 83% of the objects fell in the star-forming main sequence of galaxies, while only 8% could be considered as starbursts. We found a decreasing qPAH trend with increasing AV and consequently LIR, suggesting the possible presence of compact star-forming regions. We compared the qPAH values with the known relations of the PAH luminosities, but they did not always follow the same trends (SFR, LIR), and showed only slight correlation with the PAH luminosities.