Production Of Polycyclic Aromatic Hydrocarbons Research Articles

Polycyclic aromatic hydrocarbons (PAHs) cycling and fates in Galveston Bay, Texas, USA.

The cycling and fate of polycyclic aromatic hydrocarbons (PAHs) is not well understood in estuarine systems. It is critical now more than ever given the increased ecosystem pressures on these critical coastal habitats. A budget of PAHs and cycling has been created for Galveston Bay (Texas) in the northwestern Gulf of Mexico, an estuary surrounded by 30–50% of the US capacity of oil refineries and chemical industry. We estimate that approximately 3 to 4 mt per year of pyrogenic PAHs are introduced to Galveston Bay via gaseous exchange from the atmosphere (ca. 2 mt/year) in addition to numerous spills of petrogenic PAHs from oil and gas operations (ca. 1.0 to 1.9 mt/year). PAHs are cycled through and stored in the biota, and ca. 20 to 30% of the total (0.8 to 1.5 mt per year) are estimated to be buried in the sediments. Oysters concentrate PAHs to levels above their surroundings (water and sediments) and contain substantially greater concentrations than other fish catch (shrimp, blue crabs and fin fish). Smaller organisms (infaunal invertebrates, phytoplankton and zooplankton) might also retain a significant fraction of the total, but direct evidence for this is lacking. The amount of PAHs delivered to humans in seafood, based on reported landings, is trivially small compared to the total inputs, sediment accumulation and other possible fates (metabolic remineralization, export in tides, etc.), which remain poorly known. The generally higher concentrations in biota from Galveston Bay compared to other coastal habitats can be attributed to both intermittent spills of gas and oil and the bay's close proximity to high production of pyrogenic PAHs within the urban industrial complex of the city of Houston as well as periodic flood events that transport PAHs from land surfaces to the Bay.

Influence of photolysis on source characterization and health risk of polycyclic aromatic hydrocarbons (PAHs), and carbonyl-, nitro-, hydroxy- PAHs in urban road dust.

In this study, PAHs and their transformed PAH products (TPPs) in road dust were subjected to UV driven photolysis, and then extracted using simultaneous pressurized fluid extraction, and analysed using Shimadzu Triple Quadrupole GC/MS. The results of the analysis were used to investigate the robustness and reliability of 14 existing diagnostic ratios (DRs) and two newly proposed molecular DRs that are relevant for characterizing the sources of PAHs and TPPs. The influence of photolysis on the carcinogenic health risk posed to humans by these hazardous pollutants was then assessed. The findings indicated that the DRs segregated into stable, moderately stable and non-stable classes of source characteristics under the influence of photolysis. Only two of the existing DRs, namely, benzo(a)pyrene/benzo(ghi)perylene (BaP/BghiP) and total index exhibited consistent stability to photolysis, whilst fluoranthene/(fluoranthene+pyrene) (FRT/(FRT+PYR)) showed moderate stability. The two newly proposed DRs, naphthalene/1-nitronaphthalene (NAP/NNAP) and pyrene/(1-nitropyrene+1-hydroxypyrene) (PYR/(1NPY+HPY)) were found to be highly reliable in post-emission source characterization. The cross-plots of the most stable DRs showed that traffic emissions is the primary source of PAHs, whilst post-emission photolysis is the secondary source of nitro-PAH (NPAH) TPPs. The percent resonance energy thermodynamic stability of the PAH pollutants does not exert any direct influence on the source characteristics of the DRs. Adults are more vulnerable to potential carcinogenic risks as a result of PAH and TPPs photolysis whereas negligible risk exist for children. This study contributes to a more reliable diagnosis of PAH and TPP sources and thus, to the regulatory mitigation of these hazardous pollutants thereby, promoting enhanced protection of human health and the environment.

On the use of PIV, LII, PAH-PLIF and OH-PLIF for the study of soot formation and flame structure in a swirl stratified premixed ethylene/air flame

Soot formation and oxidation are investigated in swirl stratified premixed ethylene/air flames at atmospheric pressure. The effects of both swirl and stratification are studied to understand the relationship between the flame structure, soot precursors and soot. The topology of the flame is obtained with particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) on hydroxyl radical (OH). The production of polycyclic aromatic hydrocarbons (PAHs) is investigated using PLIF by mainly probing the aromatic compounds with two benzene rings (i.e. naphthalene) that are known to actively participate in soot nucleation and growth. Soot production is investigated using laser-induced incandescence (LII), giving quantitative data on the soot volume fraction. Extensive information on the flame structure and the mechanisms of formation/consumption of soot is gathered based on the coupling of these laser diagnostics. An image analysis of velocity, OH, PAHs and soot distributions enables us to propose a scenario that describes the link between the inception, growth, aggregation and oxidation processes. In particular, the data reveal the presence of distinct zones for these processes: a thermal decomposition region in which PAHs contributes to nascent soot formation, organised as filaments along the interface between the PAH region and the inner recirculation zone (IRZ); a mixing region controlled by large moving structures that favour the growth and aggregation of nascent soot into mature soot; and an oxidation region leading to the fast consumption of soot particles. These processes are impacted to varying extents by the intensities of swirl and stratification.

Polycyclic aromatic hydrocarbon content in sausage smoked using a Polish traditional method.

Smoking is one of the oldest and most frequently used methods of preserving meat and its products. In Poland, smoking using a traditional method is still a commonly practised form of preserving meat products. It is conducted in smoking chambers, using a process in which the hardwood of deciduous trees with the level of humidity between 10% and 30% is burnt as the source of smoke and heat. The aim of this research was to assess the impact of selected polycyclic aromatic hydrocarbons (PAHs) on traditionally smoked sausage, a cured meat product. The presence of PAHs in the environment and food products is undesirable due to their proven carcinogenic, mutagenic and teratogenic properties. In the present study, the level of four PAHs, which included benzo(a)pyrene, chrysene, benzo(a)antracene and benzo(b)fluoranthene, was measured using highperformanceliquid chromatography. The temperature in the furnace was maintained between 600 and 850°C. The duration of smoking was varied – 4-5, 5-6, 6-7 and 7-8 hours. Results showed that the time span of traditional smoking influences the products’ benzo(a)pyrene, benzo(a)antracene and benzo(b)fluoranthine contamination levels. The concentration of PAHs in products with the smoking time of 6-7 and 7-8 hours was higher than the concentration observed in products with a shorter smoking time. The changes in the sum of the concentrations of the four analysed PAHs resulted from the changes in the concentration of each hydrocarbon separately. Benzo(a)anthracene content was within the range of 11.17 and 14.19 μg/kg while the content of benzo(a)pyrene was between 4.15 and 7.69 μg/kg. The average value of benzo(b)fluoranthene was between 4.99 and 7.75 μg/kg. Chrysene contamination was within the range of 9.85 and 10.77 μg/kg. Moreover, it was found that the aggregate content of the analysed PAHs significantly exceeds the limits specified in European Union regulations. Since September 1, 2014, the limits were decreased to 2.0 μg/kg (benzo(a)pyrene) and 12.0 μg/kg (sum of four PAHs), respectively. The results suggest that the prolonged smoking process conducted in high temperature may be an impediment to approving the examined products for marketing. Key words: smoking, food, safety, PAHs, quality management, smoking time, traditional smoking

Comparison of the Fe2+/H2O2 and Fe2+/PMS systems in simulated sludge: Removal of PAHs, migration of elements and formation of chlorination by-products

In this study, polycyclic aromatic hydrocarbons (PAHs) at practical concentrations in the simulated sludge treated by the Fe2+/H2O2 and Fe2+/peroxymonosulfate (PMS) systems were evaluated in terms of the PAHs (phenanthrene, anthracene, fluoranthene) removal, element migration, Cl− effect, and chlorination by-product formation. The results indicated that according to the removal rate of PAHs, the optimal dosage of the Fe2+/PMS system (∑PAHs removal rate was 64.66 ± 2.82 %) was 1/30 of that for the Fe2+/H2O2 system (∑PAHs removal rate was 78.63 ± 0.38 %). The elemental contents in the simulated sludge were mainly affected by the extent of advanced oxidation and the amount of generated iron flocs. By studying the PAHs removal, free chlorine formation, total organochlorine content, and PAHs products in Fe2+/H2O2/Cl- and Fe2+/PMS/Cl- systems, it was found that chlorine radicals (·Cl) had high reactivity with phenanthrene and fluoranthene, whereas dichloride anion radicals (Cl2·-) exhibited the opposite behavior. Furthermore, PAHs were oxidized by ·Cl and hydroxyl radical in the Fe2+/H2O2/Cl- system, whereas PAHs and their products were chlorinated by free chlorine and ·Cl in the Fe2+/PMS/Cl- system to six chlorinated by-products such as Cl-PAHs (9-Cl-phenanthrene, 2-Cl-anthracene, 9,10-Cl2-anthracene, 3-Cl-fluoranthene). These results provide some useful suggestions for the safe advanced oxidation process treatment of textile dyeing sludge.

Characteristics of the catalytic fast pyrolysis of vegetable oil soapstock for hydrocarbon-rich fuel

Hydrocarbon-rich fuel from vegetable oil soapstock is potentially a good alternative to conventional fossil-derived fuels. This paper reported on pyrolysis experiments with compounds including vegetable oil soapstock, sodium stearate(C18), sodium palmitate(C16), sodium oleate(C18:1), and sodium linoleate(C18:2). The effects of pyrolysis temperature, HZSM-5 catalyst, unsaturation degree and carbon chain length on the formation of aromatic hydrocarbons were explored. Experimental results indicated that the relative content of oxygenated compounds significantly decreased in the condensable organic compounds of soapstock pyrolysis, and aromatic hydrocarbons increased when the HZSM-5 catalyst was used, in which toluene and xylene had the highest relative selectivity. High catalytic pyrolysis temperature was beneficial to the relative selectivity of benzene and toluene, but inhibited the relative selectivity of xylene and ethylbenzene. The increase in saturation of fatty acid salts promoted the reaction toward the production of polycyclic aromatic hydrocarbons, which were a kind of typical precursor of catalyst coking deactivation and carcinogenic pollutants.

Application of multivariate data techniques in photochemical study of polycyclic aromatic hydrocarbons (PAHs) and transformed PAH products in road dust.

Road dust is a key repository for PAHs and transformed PAH products (TPPs) generated from natural and anthropogenic sources in the urban environment. Eventhough PAHs and TPPs are prone to post-emission photochemical processes, very limited studies exist on the subject for road dust. This knowledge gap is of particular concern since some of the resultant TPPs are notably more carcinogenic than their precursor PAHs. This study evaluated the role of 254nm ultraviolet (UV) photons on the photochemistry of PAHs and TPPs in road dust. The findings show that UV irradiation had varying effects on the fate of analytes, particularly naphthalene (NAP), phenanthrene (PHE), 7, 12-dimethylbenz(a)anthracene (DMBA), 1-hydroxypyrene (HPY), 1-nitropyrene (1NPY), pyrene (PYR) and 5-nitroacenaphthene (5NAC). Photochemical relationship was identified between PYR, 1NPY and HPY, and DMBA and benzo(a)anthracene. Unlike carbonyl-PAHs, parent PAHs, nitro-PAHs and hydroxy-PAHs can originate from photolysis. Photon irradiation durations of 3, 6 and 7.5h had the most intense influence on the photolytic process with 7.5h as optimum. The photochemical rate at optimum irradiation duration shows an increasing trend of NAP<PHE < 1NPY<DMBA < 5NAC<HPY with respective estimates of 0.08, 0.11, 0.21, 0.22, 0.43, and 0.59mgkg-1 hr-1. Physicochemical properties of analytes such as index of refraction and vapour pressure (in logarithmic form) had an inverse effect on photolysis. The knowledge generated is significant for the in-depth understanding of the fate of PAHs and TPPs on urban road surfaces and contributes to the greater protection of human health and the environment.

Enhancing the degradation of mixed polycyclic aromatic hydrocarbon and medium-chain-length polyhydroxyalkanoate production by mixed bacterial cultures using modified repeated batch fermentation.

To increase the biodegradation of phenanthrene (PHE), pyrene (PYR) and fluoranthene (FLU) through mixed cultures of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria, using modified repeated batch fermentation. Novel bacterial strains of Pseudomonas putida, Pseudomonas sp. and Ralstonia eutropha were cultivated and the biodegradation and conversion of mixed PAH to medium-chain-length polyhydroxyalkanoates (MCL-PHA) was determined. The highest degradation of PAH (100%) and PHA production (50·0%) was obtained in medium containing 30mmoll-1 of mixed PAH after three cycles of repeated batch fermentation. The concentration of PAH in the reactor was increased from 30 to 90mmoll-1 with repeated additions of PAH, and bacteria were able to produce PHA at 40% of cell dry mass. The MCL-PHA were identified by gas chromatography/mass spectroscopy, with the 3-hydroxydecanoate (3-HD) monomer higher than 75mol.%. This study demonstrated that the biodegradation of PHE, PYR and FLU was enhanced by modified repeated batch fermentation using a mixed culture of bacteria. In addition, this fermentation strategy also increased the production of PHA, with an increase in monomer composition. This was the first study to describe the enhancement of the degradation of mixed solutions of PHE, PYR and FLU, and PHA production, using novel mixed bacterial cultures and modified repeated batch fermentation. The MCL-PHA formed had uniquely high 3-HD content.

Problems of polycyclic aromatic hydrocarbons studying in the waters of North-Eastern Caspian Sea

The problems of studying the negative factors of oil and gas activity in the waters of the North-Eastern Caspian Sea are presented. Despite the active anthropogenic activity, the specificity of hydrocarbon pollution in this part of the water area is poorly understood. The approaches to the analysis of the qualitative composition and identification of sources of polycyclic aromatic hydrocarbons (PAHs) pollution based on the indicator ratios of kinetic and thermodynamic isomers are presented. These approaches make it possible to identify the source of pollution, but a full assessment requires taking into account the seasonal dynamics of the sta- tus of aquatic systems. Estimates of the migration features of PAHs and their definitions in the aqueous phase are given. The problems of transition and the study of polyarenes to bottom sediments are assessed. The issues of the degradation of PAH and oil products in the aquatic systems of the region are considered, recommendations are given to improve the development of the research base of the reviewed topics.

Theoretical Study of PAH Growth by Phenylacetylene Addition.

Although there was significant advancement on polycyclic aromatic hydrocarbon (PAH) formation, current mechanisms are still limited in providing an integrated and accurate scheme of PAH yield in combustion conditions; thus, a more detailed and comprehensive understanding is necessary. This work provides a systematic investigation of PAH growth by phenylacetylene addition. A combination of the density functional theory (DFT/B3LYP/6-311+G(d,p)) and the complete basis set method (CBS-QB3) is utilized to calculate the potential energy surfaces. The reaction system is initiated by the H elimination reaction of phenylacetylene + H → o-ethynylphenyl + H2, and then, the addition reaction of phenylacetylene and o-ethynylphenyl can produce PAHs with one, two, three, and four rings. The temperature- and pressure-dependent reaction rate coefficients are calculated via a combination of conventional transition state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory with solving the master equation in the temperature range of 500-2500 K and at the pressure range of 0.01-10 atm. There are 263 species and 65 reactions in this reaction system. It shows that the rate constants of this reaction system are highly temperature-dependent and slightly sensitive to the pressure at temperatures lower than 1300 K. To evaluate the yield distributions of various PAH products in the whole reaction network, a closed 0-D batch reactor model in Chemkin is used to calculate the C6H5C2H-C2H2-H-Ar reaction system. The results showed that the prevailing products of this system are three-ring PAHs with side chain structures. Compared with the traditional HACA pathways, the investigated reaction system presents higher efficiency in large PAH formations, which could subsequently promote the formation of soot particles. The phenylacetylene and o-ethynylphenyl reaction network emphasizes the importance of species with side chains, and it enriches current PAH growth pathways aside from the addition of small species such as C2H2.

Forest fires as potential triggers for production and mobilization of polycyclic aromatic hydrocarbons to the terrestrial ecosystem

AbstractAlthough forest fires have been identified as an important source of polycyclic aromatic hydrocarbons (PAHs), this problematic has not been thoroughly studied yet. This study addressed the role of wildfires and time since fire in the production and mobilization of PAHs to the terrestrial compartment. Levels of 15 priority PAHs were assessed in topsoil and ash samples (by GC–MS analysis) collected in two burnt areas and an unburnt one, comprising two types of vegetation coverage and four sampling occasions after fire. The fire had triggered an immediately increase of PAH levels in topsoil, according to the comparison of burnt and unburnt samples, but this impact had largely faded 4 months later. Although the fire severity did not play a role in immediate postfire PAH contents in topsoil and ashes, variations were found with the type of vegetation coverage being higher in pine slopes. The wildfire event markedly changed PAHs composition through enrichment in three‐ring PAHs (69% vs. 27%, burnt and unburnt, respectively), which dwindled more markedly in topsoil than in ashes. This study pointed out the key role of wildfires as a source of PAHs to the terrestrial compartment, as unveiled by the increased levels in topsoil and ashes. Additionally, it was found that PAHs could be mobilized from these matrixes over the first year after the fire, possibly leading to aquatic contamination. This finding suggests wildfires as a diffuse source of PAH contamination to freshwater systems, which need to be considering in future monitoring/management programs on the environmental impact of wildfires.

Phenolic compounds in beer inhibit formation of polycyclic aromatic hydrocarbons from charcoal-grilled chicken wings

The effect of various beer marinades on formation of polycyclic aromatic hydrocarbons (PAHs) in charcoal-grilled chicken wings (CWs) and the active ingredients in beer contributing to inhibition of PAH formation were studied. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and total phenolic content (TPC) of six beers were evaluated. LC-MS analysis indicated a total of 32 phenolic compounds, among which we screened 11 to verify the inhibition of select PAH production. The total stable free radicals and selected PAH content of charcoal-grilled CWs were assayed, revealing a positive correlation. Heineken exhibited the highest phenol content and excellent performance in TPC (393.86 mg gallic acid equivalents (GAE)/L), ability to scavenge free radicals (27.0%), and the most effective inhibition of PAH8 formation (67%). Our study supplies a theoretical foundation for using edible materials rich in phenolic compounds as potential natural inhibitors of PAHs formed during the cooking process.

The Potential Environmental Impact of PAHs on Soil and Water Resources in Air Deposited Coal Refuse Sites in Niangziguan Karst Catchment, Northern China.

Long-term deposition of coal spoil piles may lead to serious pollution of soil and water resources in the dumping sites and surrounding areas. Karst aquifers are highly sensitive to environmental pollution. In this study, the occurrence and release/mobilization of polycyclic aromatic hydrocarbons (PAHs) in coal waste and coal spoils fire gas mineral (CSFGM) were evaluated by field and indoor investigations at Yangquan city, one of the major coal mining districts in the karst areas of northern China. Field investigations showed that dumping of coal waste over decades has resulted in soil and water pollution via spontaneous combustion and leaching of coal spoil piles. Indoor analysis revealed that the 2-ring and 3-ring PAHs contribute to 65–80% of the total PAHs in coal spoils, with naphthalene (Nap), Chrysene (Chr), and Phenanthrene (Phe) as the dominant compounds. Based on a heating/burning simulation experiment, the production of PAHs is temperature-dependent and mainly consists of low-ring PAHs: 2-ring, 3-ring, and part of the 4-ring PAHs. The PAHs in the leachate are light-PAHs (Nap, 20.06 ng/L; Phe, 4.76 ng/L) with few heavy-PAHs. The distribution modes of PAHs in two soil profiles suggest that the precipitation caused downward movement of PAHs and higher mobility of light-PAHs.

Influence of pyrolysis temperature on polycyclic aromatic hydrocarbons production and tetracycline adsorption behavior of biochar derived from spent coffee ground

The main objective of this study was to evaluate the effect of different pyrolysis temperatures on the formation of polycyclicaromatichydrocarbons (PAHs) in biochar originated spent coffee ground (SCG) and the tetracycline (TC) adsorption behavior of biochar in water. The results showed that biochar synthesized at 500 °C (SCG 500) contained low PAHs (600 µg kg−1) and the highest TC adsorption efficiency. In addition, the characteristics, influencing factors on TC adsorption, and the related mechanisms of SCG 500 were comprehensively investigated. The results showed that the highest efficiency was observed at pH of 7 and the presence of ions in salinity solution reduced the adsorption capacity of SCG 500. The electrostatic interaction, hydrogen bonding, and π-EDA were the major adsorption mechanisms. Safety PAHs level, low-cost, widely material sources and high TC removal capacity suggested that SCG 500 was a promising environmentally friendly effective absorbent.

Fluoranthene Biodegradation by Serratia sp. AC-11 Immobilized into Chitosan Beads.

The intensive production of polycyclic aromatic hydrocarbons by anthropogenic activities is a serious environmental problem. Therefore, new bioremediation methods are required to avoid widespread contamination. In this work, Serratia sp. AC-11 strain isolated from a tropical peat was selected for immobilization into chitosan beads, which were employed in the biodegradation of fluoranthene. The sizes of the produced beads were relatively uniform with an average diameter of 3mm. The material was characterized by SEM and FT-IR, confirming the cells immobilization and the protective barrier formed by the chitosan surrounding the biomass. The immobilized bacteria were able to degrade 56% of fluoranthene (the initial concentration was 100mgL-1) in just 1day at twice the degradation rate achieved by free-living cells. Furthermore, the immobilized bacteria showed excellent removal during five reuse cycles, from 76% to 59% ofbiodegradation. These results showed the potential of this approach for remediation of contaminated sites.

Effect of catalysts on distribution of polycyclic-aromatic hydrocarbon (PAHs) in bio-oils from the pyrolysis of dewatered sewage sludge at high and low temperatures

This study was aimed at investigating the effect of four types of catalysts on the distribution characteristics of 16 polycyclic-aromatic hydrocarbon (PAHs) in bio-oils from the pyrolysis of dry sewage sludge. The pyrolysis experiments of sewage sludge were conducted in a tubular reactor at the high and low temperatures of 850 °C and 450 °C, respectively. CaO, KCl, Na2CO3, and Fe2O3were selected as catalysts for the catalyzed pyrolysis. In the non-catalyzed sludge pyrolysis, PAHs concentrations in bio-oil increased with temperature, reaching a maximum value of 15.25 μg/g at 850 °C. This value was 4.5 times higher than PAHs concentration from the non-catalyzed pyrolysis at 450 °C. With the presence of catalysts at 850 °C, an evident reduction of PAHs concentration was observed for all the bio-oil samples. The added catalysts proved to effectively inhibit PAHs formation in bio-oil and reduce the toxic equivalent quantity (TEQ) of PAHs in the experiment at high temperature. The lowest observed PAHs concentration in bio-oil was 4.23 μg/g, obtained with the use of KCl catalyst. However, an opposite trend was observed for catalyzed pyrolysis at 450 °C. The added catalysts promoted PAHs formation, up to the concentration of 8.89 μg/g with the use of CaO catalyst. Catalyst loading also influenced PAHs concentration and TEQ, with the lowest output found at 20% loading for all catalysts. Bio-oil yields, mass ratio of 16 PAHs concentrated into bio-oil, the TEQ of 16 PAHs and their subtotal group classified by ring number were separately examined to analyze their effects on fractional distribution of the total PAH amount. Overall, the presence of the selected catalysts was found to have the ability to inhibit PAHs production at higher pyrolysis temperature and to promote PAHs production at lower pyrolysis temperature.

A sensor array for the discrimination of polycyclic aromatic hydrocarbons using conjugated polymers and the inner filter effect.

Natural and anthropogenic activities result in the production of polycyclic aromatic hydrocarbons (PAHs), persistent pollutants that negatively impact the environment and human health. Rapid and reliable methods for the detection and discrimination of these compounds remains a technological challenge owing to their relatively featureless properties, structural similarities, and existence as complex mixtures. Here, we demonstrate that the inner filter effect (IFE), in combination with conjugated polymer (CP) array-based sensing, offers a straightforward approach for the quantitative and qualitative profiling of PAHs. The sensor array was constructed from six fluorescent fluorene-based copolymers, which incorporate side chains with peripheral 2-phenylbenzimidazole substituents that provide spectral overlap with PAHs and give rise to a pronounced IFE. Subtle structural differences in copolymer structure result in distinct spectral signatures, which provide a unique "chemical fingerprint" for each PAH. The discriminatory power of the array was evaluated using linear discriminant analysis (LDA) and principal component analysis (PCA) in order to discriminate between 16 PAH compounds identified as priority pollutants by the US Environmental Protection Agency (EPA). This array is the first multivariate system reliant on the modulation of the spectral signatures of CPs through the IFE for the detection and discrimination of closely related polynuclear aromatic species.

Small Molecular Weight Aldose (d-Glucose) and Basic Amino Acids (l-Lysine, l-Arginine) Increase the Occurrence of PAHs in Grilled Pork Sausages.

(1) Background: Amino acids and carbohydrates are widely used as additives in the food industry. These compounds have been proven to be an influencing factor in the production of chemical carcinogenic compounds polycyclic aromatic hydrocarbons (PAHs). However, the effect of the properties of the amino acids and carbohydrates on the production of PAHs is still little known. (2) Methods: We added different (i) R groups (the R group represents an aldehyde group in a glucose molecule or a ketone group in a fructose molecule); (ii) molecular weight carbohydrates; (iii) polarities, and (iv) acid-base amino acids to pork sausages. The effects of the molecular properties of carbohydrates and amino acids on the formation of PAHs in grilled pork sausages were investigated. (3) Results: The results showed that a grilled sausage with aldehyde-based d-glucose was capable of producing more PAHs than a sausage with keto-based d-fructose. A higher PAH content was determined in the grilled pork sausage when the smaller molecular weight, d-glucose, was added compared with the sausage where the larger molecular weight, 4-(α-d-glucosido)-d-glucose and cellulose were added. The addition of basic amino acids (l-lysine, l-arginine) was capable of producing more PAHs compared with the addition of acidic amino acids (l-glutamic acid, l-aspartate). When amino acid containing a benzene ring was added, a smaller volume of PAHs was produced compared with the addition of other amino acids. (4) Conclusions: Our study suggests that systematic consideration of molecule properties is necessary when using food additives (amino acids and carbohydrates) for food processing.

Polycyclic aromatic hydrocarbons formation and growth during the supercritical pyrolysis of 1-octene

To better understand the roles of larger 1-alkenes in reactions leading to the production of polycyclic aromatic hydrocarbons (PAH) and solids in the supercritical pre-combustion environments of future-high-speed-aircraft fuels, supercritical pyrolysis experiments have been conducted with the model fuel 1-octene, a representative 1-alkene product of supercritical n-alkane-fuel pyrolysis. The 1-octene pyrolysis experiments are performed in an isothermal, silica-lined stainless-steel flow reactor at 94.6 atm, 133 s, and ten temperatures in the range 440–535 °C. Straight-chain aliphatics—particularly n-alkanes, 1-alkenes, and 2-alkenes—are the highest-yield products at all temperatures. At temperatures ≤500 °C, high yields of the C8 product 2-octene and the C16 product 6-hexadecene evidence 1-octene's facile formation of the resonance-stabilized alkylallylic radical 1-octen-3-yl, whose resonance structure 2-octen-1-yl not only abstracts H to produce 2-octene but also reacts with 1-octene to produce, with high selectivity, 6-hexadecene—establishing that, at low temperatures, a long-chain alkene with an interior CC double bond can result from alkylallyl-radical addition to a 1-alkene. Gas-chromatographic analyses of 1-octene's aromatic products show that one- and two-ring aromatics are produced at temperatures ≥ 475 °C. High-pressure-liquid-chromatographic analyses reveal the identities of 180 three- to nine-ring PAH products—178 of which have never before been identified as pyrolysis products of a large 1-alkene and all of which are produced from supercritical n-decane pyrolysis as well. As in the case for n-decane, the high levels of methyl-substituted PAH in the 1-octene products provide a ready source for resonance-stabilized arylmethyl radicals and (after reaction with ethylene) phenalenyl-type radicals. Reactions of these arylmethyl and phenalenyl-type radicals with C2C4 1-alkenes lead to the sequential PAH growth that accounts for 1-octene's production of PAH as large as nine rings at temperatures as low as 500 °C and the dramatic increases in the PAH-product yields as temperature approaches 535°C, 1-octene's temperature of incipient solids formation.

Comprehensive assessment of the content of polycyclic aromatic hydrocarbons and dependence of their accumulation in meat products

Dependences of the quantity of polycyclic aromatic hydrocarbons (PAH) on the conditions for the formation of components of smoke compositions, the type of wood, the formulation, the technology of production, and the type of packaging material have been studied. An increase in temperature from 450 to 700 °C lead to a 2-3-fold increase in the amount of PAH in meat products. It has been established that the use of a polyamide coating reduced the total carcinogenicity of sausages by 2.0-3.7 fold compared with protein and natural shells, which in terms of PAH accumulation were the most dangerous. Fibrous shell was able to provide a reduction in PAH level in the product up to 40% compared to natural one. The permeability of the fat fraction of the product for PAH was up to 10 fold higher than that of proteins and carbohydrates. The data obtained made it possible to determine the safety criteria for smoked meat products, taking into account the potential carcinogenic hazard of each PAH. The optimal indicators of the presence of PAH in the product are 8 PAH (benz[a]pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, dibenz[a,h]anthracene, indeno[1,2,3-c,d] pyrene). The PAH exposure on the human body has been determined under the constant consumption of smoked meat products. The prospective use of barrier protection technologies, substances possessing antiradical activity, and protective films to reduce residual PAH content has been proved. The results of the studies showed a 5-fold decrease in the total amount of PAH when using films impregnated with fat-containing micro anemulsion of vegetable or animal fat. The effect increased when meat was marinateв in a 9% solution of acetic acid or 3% solution of ascorbic acid.