Amount Of Polycyclic Aromatic Hydrocarbons Research Articles

Soil texture as a key driver of polycyclic aromatic hydrocarbons (PAHs) distribution in forest topsoils

Due to the dynamic development of civilization and the increasing demand for energy, pollution by harmful chemicals, including polycyclic aromatic hydrocarbons (PAHs) compounds, is a serious threat to forest soils. The aim of the study was to determine the role of texture in the distribution of polycyclic aromatic hydrocarbons (PAHs) and trace elements in forest soils. The areas with different texture ranging from sand through sandy loam to silt loam were selected for the study. The study was carried out in the Chrzanów Forest District in southern Poland (50° 7′ 18 N; 19° 31′ 29 E), which in one of the most intensive industrial emission zones in Europe. The soil samples for properties determination were collected from locations distributed on a regular grid 100 × 100 m (20 points). The samples were collected from the humus horizon (0–10 cm) after removing organic horizon. Basic chemical properties, heavy metal content, polycyclic aromatic hydrocarbons (PAHs) content and magnetic susceptibility values were determined in soil samples. Additionally, enzymatic activity and microbiological biomass was determined in the samples. Our study confirmed the importance of texture in PAHs distribution. A strong correlation between PAHs content and silt content in the soils studied was noted. The regression tree analysis confirmed the importance of the silt content, followed by soil organic carbon in PAHs distribution. Organic carbon content and nitrogen content played a predominant role in controlling the microbial activity. In our study, we did not note a relationship between enzymatic activity, microbiological soil biomass and the amount of PAHs. This may be due to the effective sorption and immobilization of PAHs by particles of fine fractions, especially silt. Obtained results confirmed the usefulness of magnetic susceptibility in the assessment of heavy metals contamination of forest soils. We noted high correlation between magnetic susceptibility value and heavy metals content. Moreover, the relationship between magnetic susceptibility and soil texture of the topsoil was also observed.

Leaching behavior of polycyclic aromatic hydrocarbons (PAHs) from oil-based residues of shale gas drill cuttings

Cuttings are the main solid residues which are generated from drilling operations. Due to the presence of heavy and radioactive elements, the environment risk posed by cuttings has attracted increasing attention. In this work, a short-term static immersion experiment was carried out to investigate the leaching of polycyclic aromatic hydrocarbons (PAHs) from oil-based residues of shale gas drilling cuttings. Furthermore, the effects of some relevant environmental factors controlling the leaching behavior were evaluated, including the different particle sizes, pH, extraction time, solid-to-liquid (S/L) ratio and dissolved organic matter (DOM) concentration. The results showed that (1) the concentrations of leached PAHs gradually increased with prolonged leaching time, but the cumulative amount of PAHs released during leaching was less than 3% of the total. (2) The Elovich, parabolic diffusion and power function models were found to fit the experimental data better than the first-order kinetic equation, indicating that the leaching of PAHs was controlled by the coupling of diffusion and chemical reactions at the source surface. (3) Different environmental factors had different impacts on the leaching of PAHs: the shaking time and presence of DOM increased leachability, the particle size and S/L ratio decreased leachability, and the pH did not affect the leachability of PAHs. Therefore, PAHs leaching was a complex process, and it is of scientific and environmental interest to conduct the leaching tests under the simulated environmental conditions.

Polycyclic aromatic hydrocarbons in fine road dust from a coal-utilization city: Spatial distribution, source diagnosis and risk assessment

Coal combustion can release large amounts of polycyclic aromatic hydrocarbons (PAHs), which persist in various environment matrices (e.g., road dust) and hence cause the carcinogenic risk to human health. In this study, an exhaustive characterization of road dust samples coupling their physicochemical characteristics and stable isotope compositions (δ13C and δ15N) was conducted to evaluate the source, level, spatial distribution, and carcinogenic risk of PAHs in a typical coal-utilization city. Concentrations of Σ16 PAHs ranged from 605.5 to 25,374.3 ng/g with a mean concentration of 4083.0 ng/g. Pollution levels of sites around the coal-fired power plant (Zone 1) were significantly higher than those in other zones (p < 0.05). PAH concentration showed significant correlations with both C and N fractions (p < 0.01). Compositions of δ13C and δ15N in road dust coupled to principal component analysis and the partitions and diagnostic ratios of PAHs contributed to associating road dust to several local sources of contamination. Coal combustion and vehicular exhaust were major sources of PAHs around the power plant and urban area. Results of incremental lifetime cancer risk showed 81.5% of all sampling sites suffered potential risk (>10−6) for both adults and children, while children around the power plant suffered the highest risk. Despite the estimation of only potential risk being posed by PAHs in road dust, human exposure to the various environmental matrices, scientific and systematic assessment of carcinogenic risks by PAHs in the total environment warrants further investigations.

The distribution and retained amount of benzo[a]pyrene at the micro-zones of mangrove leaf cuticles: Results from a novel analytical method

Plant leaf cuticles play a critical role in the accumulation and transport of atmospheric polycyclic aromatic hydrocarbons (PAHs). The relationship between the distribution and retained amount of PAHs on the leaf cuticles and the leaves micro-zone structures is still unclear. In this study, a confocal microscopic fluorescence spectral analysis (CMFSA) system with a spatial resolution of 200 nm was established as a direct and noninvasive means to determine the microscopic distribution and quantify the retained amount of benzo[a]pyrene (B[a]P) at Aegiceras corniculatum (Ac), Kandelia obovata (Ko) and Avicennia marina (Am) leaf cuticle micro-zones (0.096 mm2). The linear ranges for the established method were 10–1900 ng spot−1 for Ac, 15–1700 ng spot−1 for Ko and 30–1800 ng spot−1 for Am, and the detection limits were 0.06 ng spot−1 for Ac, 0.06 ng spot−1 for Ko and 0.07 ng spot−1 for Am. Notably, B[a]P formed clusters and unevenly distributed at the leaf cuticles. On the adaxial cuticles, B[a]P was mainly accumulated unevenly along the epidermis cell wall, and it was also distinctively distributed in the secretory cells around salt glands for Ac and Am. On the abaxial leaf cuticles, B[a]P was concentrated in the salt glands and stomata apart from being unevenly distributed in the epidermis cell wall. Moreover, the amount of B[a]P retained presented a negative correlation with the polarity of leaf cuticles, which resulted in the amount of B[a]P retained on the adaxial leaf cuticles being significantly higher than that on abaxial leaf cuticles. Our results provide a potential in situ method for investigating the distribution and retained amount of PAHs at plant leaf surface micro-zones, which would contribute to further studying and understanding the mechanism of migration and transformation of PAHs by plant leaves from a microscopic perspective.

Monitoring the aerosol solids deposited in snow in the area affected by the technological road of the Gorlov anthracite mining pit (Novosibirsk region, Russia)

The aim of the study. To monitor and assess the chemical composition of the solid aerosols deposited in the snow in the area affected by the technological road of the Gorlov anthracite mining site. Location and time of the study. The study was conducted in the Iskitim district of the Novosibirsk region (54.58o N, 83.57o E) in 2018–2020. Methodology. The content of total solids in snow was measured by gravimetric method after filtering the melted snow sample through the filter with 0.22 µm mesh size. Micromorphology of the solids was studied by using scanning electron microscope Hitachi TM-3000 (Japan) with attached EDS detector console Bruker Quantax 70 for the element analysis of the surface. The carbon content, С/Н and C/N ratios were determined by dry combustion using the СHN-analyzer (Perkin Elmer 2400 Series II, USA). The content and composition of polycyclic aromatic hydrocarbons (PAH) were determined by gas chromatography using Agilent Technologies АТ 6890N with AT 5975N mass-selective detector and AT 7683B autosampler. Main results. The article presents the results of the three-years long study of the solids accumulated in snow along the technological road in the north of the Gorlov anthracite basin. The influence of the automobile road used for the anthracite transportation was shown to reach as far as 2000 m in all directions. The snow cover was found to accumulate from 1.4 to 1131.6 g/m2 of deposited aerosol solids. Those solids were mostly represented by coal particles, the carbon content ranging 26.5–64.1% and increasing with the distance from the road. The aerosol solids, accumulated in snow, were found to contain significant amounts of PAH, including the carcinogenic ones. In the snow samples collected at 25–2000 m off the road, carcinogenic PAH content was found to be 9–13000 times higher than at the control site remoted from the road. Conclusion. The presented study helped to elucidate the factors, contributing to decreasing the spread of the anthracite solids during automobile transportation. Such spread can be attained by a) establishing wide multi-storeyed forested protective belts along technological automobile roads; b) compulsory covering of the loads in the coal-transporting vehicles; c) decreasing the speed limit of the vehicles; and d) taking into consideration a wind rose while projecting locations new automobile roads and coal mining spoils.

Assessment of polycyclic aromatic hydrocarbons (PAHs) in traditional breads consumed by people in Tehran city of Iran and the calculation of their daily intake

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are stable organic pollutants with proven carcinogenic properties. These substances produced as a result of incomplete burning of fossil fuels. Due to PAHs importance in people’s health, we decided to design a study to measure the amount of polycyclic aromatic hydrocarbons (PAHs) in different types of traditional bread produced in Tehran city and calculate their daily intake by consumers. Seventy-five samples of five types of bread including Lavash, Tafton, Sangak, and Barbary and bulk were randomly collected from bakeries in the city of Tehran to investigate the amount of PAHs. All extracted samples were measured by Gas chromatography–mass spectrometry (GC-MS). The separation of PAHs performed based on a solid phase magnetic extraction (MSPE) method with carbon nanotubes prepared from bread samples and the extracted samples were measured by GC-MS. Our finding showed that the mean values of aromatic hydrocarbon compounds (PAH) in the bread samples range from 0.2 to 8.7 μg kg-1. The maximum amount of aromatic hydrocarbon compounds (PAH) was in Barbary bread with amount of 8.7 µg kg−1 and the minimum value was in industrial bread (bulk) with 0.2 µgkg−1. Also, the mean value ofPAHs content in Sangak, lavash, and bulk (industrial) bread was 2.25, 2.5 and 1.66 µg kg−1, respectively. The highest and lowest mean value of aromatic hydrocarbon polycyclic compounds (PAHs) were obtained in barbaribread around 2.64 μg kg−1 and 1.59 μg kg-1 in Taftoon, respectively. Also,the result of this study showed that the Daily intake of benzopyrene in bread by consumers was below international recommended levels. According to the results, long time and high-temperature baking, also the thickness of the bread, is the main contributor of high concentration of PAHs in the bread.

Concentrations and Sources of Atmospheric PM, Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons in Kanazawa, Japan

PM2.5 (fine particles with diameters 2.5 micrometers and smaller) and PM&gt;2.5 were separately collected in Kanazawa, Japan in every season, from the spring of 2017 to the winter of 2018, and nine polycyclic aromatic hydrocarbons (PAHs) and six nitropolycyclic aromatic hydrocarbons (NPAHs) were respectively determined using high-performance liquid chromatography (HPLC) with fluorescence and chemiluminescence detections. The atmospheric concentrations of both the PAHs and NPAHs showed seasonal changes (highest in the winter and lowest in the summer), which differed from the variations in the total suspended particulate matter (TSP) and PM2.5 amounts (which were highest in the spring). The contributions of major sources to the combustion-derived particulate (Pc) in the PM2.5 were calculated using the 1-nitropyrene-pyrene (NP) method, using pyrene and 1-nitropyrene as the representative markers of PAHs and NPAHs, respectively. The annual average concentration of Pc accounted for only 2.1% of PM2.5, but showed the same seasonal variation as PAHs. The sources of Pc were vehicles (31%) and coal heating facilities/industries (69%). A backward trajectory analysis showed that the vehicle-derived Pc was mainly from Kanazawa and its surroundings, and that coal heating facilities/industry-derived Pc was transported from city areas in central and northern China in the winter, and during the Asian dust event in the spring. These results show that large amounts of PAHs were transported over a long range from China during the winter. Even in the spring, after the coal heating season was over in China, PAHs were still transported to Japan after Asian dust storms passed through Chinese city areas. By contrast, the main contributors of NPAHs were vehicles in Kanazawa and its surroundings. The recent Pc concentrations were much lower than those in 1999. This decrease was mostly attributed to the decrease in the contribution of vehicle emissions. Thus, the changes in the atmospheric concentrations of Pc, PAHs and NPAHs in Kanazawa were strongly affected not only by the local emissions but also by long-range transport from China.

Selectively Determination Trace Amounts of Polycyclic Aromatic Hydrocarbons from Water and Wastewater Matrices Using Graphitic Carbon Nitride/Layered Double Hydroxide Nanocomposite on Porous Anodized Aluminum Wire as SPME Fiber

Synthesis a well-suited coating for solid phase microextraction (SPME) fiber is essential point due to determination trace amounts of analytes from water and wastewater samples. So, the new coating was built onto the porous anodized aluminum wire incorporated with layered double hydroxide compound and modified solvothermally with graphitic carbon nitride and used as fiber coating for selectively analysis of polycyclic aromatic hydrocarbons by HS-SPME method. According to the results, this coating indicated considerable potential due to extract simultaneously trace amounts of some carcinogenic polycyclic aromatic compounds in different matrices. Essential parameters such as microextraction time, microextraction temperature, agitation speed and ionic strength of the sample solution that mainly affect the adsorption process were optimized and in the optimum values, repeatability data of one fiber that changed between 4.7% and 7.7% for the test compounds were achieved. Detection limits for the studied compounds were between 0.002 to 0.32 µg L−1. It is a simple, quick, and cheap approach. There is stability in the fiber in terms of temperature, and great recoveries are obtained by its use.

Hierarchically Synthesis of Nanoflower Layered Double Hydroxide/Molybdenum Disulfide on Electrochemically Anodized HB Pencil Lead for Determination Trace Amounts of Polycyclic Aromatic Hydrocarbons

Preparation coating materials is a fundamental point in solid-phase microextraction (SPME) fiber fabrications. So, a hydrothermal approach was developed for fabricating 3 D hierarchically molybdenum disulfide/layered double hydroxide on anodized HB pencil lead, Nanosheets of a porous molybdenum disulfide and layered double hydroxide were directionally arranged on anodized HB pencil lead and used as a fiber coating for selectively analysis of polycyclic aromatic compounds (PAHs) by headspace SPME method. The as-synthesized materials were characterized by thermal gravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, According to the results, this coating indicated considerable potential due to extracting trace amounts of some carcinogenic polycyclic aromatic compounds in water samples. The essential parameters such as extraction time, extraction temperature, agitation speed, and ionic strength of sample that mainly affect the adsorption process were optimized and in optimum values, the repeatabilities for one fiber were between 4.6% and 9.1% for the test compounds were achieved. The studied compounds were assessed within the detection limits as follows: 0.028 to 0.42 ngL−1.

Potentially Toxic Metals and Polycyclic Aromatic Hydrocarbons Composition of some Popular Biscuits in Nigeria

Evaluation of levels of potentially toxic metals (PTMs) and polycyclic aromatic hydrocarbons (PAHs) were carried out in six biscuit samples commonly consumed in Nigeria. This was done to establish the consumption safety of the biscuits with respect to the amounts of PTMs and PAHs contained. Profiling of As, Cd, Co, Cu, Mn, Pb and Zn in the acid digested biscuit samples was done using Atomic Absorption Spectrometer, while identification and quantification of the various PAHs in the extracts obtained with the aid of a Soxhlet extractor using n-hexane as the extracting solvent were achieved using Gas Chromatograph coupled with Flame Ionization Detector (GC-FID). Potentially toxic metals were detected at levels that ranged from 0.050 to 2.525 µg/g, while the PAHs concentrations ranged between below detection limit and 19.440 µg/g. For carcinogenic risk indices of the PAHs, total dietary daily intake (ΣDDI in µg/day) ranged from 0.011 in B1 to 0.315 in B6; ΣDDI for carcinogenic PAHs (mg/day) ranged from 0.001 in B3, B4, and B6 to 0.007 in B2, while the carcinogenic toxic equivalent (TEQ) values (µg/g) ranged from 0.006 in B4 to 0.089 in B2. Health risk indices evaluated for both PAHs and PTMs indicated that consumption of the biscuit products as occasional in-between meals and snacks might not constitute serious health problems.

Effects of Hydrogen Peroxide and Temperature on Removal of Polycyclic Aromatic Hydrocarbons (Pahs) from Soil during Photodegradation Applications

ABSTRACT This study investigated the removal of polycyclic aromatic hydrocarbons (PAHs) from soils around a cement factory in Bursa-Turkey. UVA and UVA-H2O2 applications were carried out with the particular apparatus. The evaporated PAHs were collected with the polyurethane foam (PUF) column in this apparatus. UVA applications were carried out simultaneously at two temperatures (18°C and 35°C) to determine the effect of temperature on PAHs’ removal. Evaporated PAH amounts and PAH removal efficiencies were calculated. In UVA applications (without using H2O2), ∑12 PAH removal efficiency was calculated as 90%, and this value increased to 95% with the use of H2O2. The highest PAH removal ratio (95%) was obtained with UVA-H2O2 (1% H2O2) application. An increase in temperature did not contribute significantly to the removal of PAHs (except for 20% H2O2). During the experiments, the amount of evaporated PAHs from soil to air increased depending on the temperature. It was observed that 80% of evaporated PAHs were formed 3 ring compounds (Phe, Ant) at 35°C. It was concluded that only low H2O2 dose (1%) was effective on the removal of PAHs from soils at 18°C and 35°C.

Ionization selectivity of electrospray and atmospheric pressure photoionization FT-ICR MS for petroleum refinery wastewater dissolved organic matter.

Dissolved organic matter (DOM) in petroleum refinery wastewater is an extremely complex mixture. A better understanding of chemical compositions of DOM at the molecular level is necessary for the design and optimization of wastewater treatment processes. In this study, two largely different DOM samples, one from a petroleum refinery wastewater and the other from the Suwannee river water, were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with positive-/negative-ion electrospray ionization (ESI), and positive-ion atmospheric pressure photoionization (APPI). For wastewater DOM, a total of 6226 molecular formulae were assigned in the three ionization modes. However, only 1182 molecular formulae were common in all three mass spectra, indicating that the techniques were highly complementary in the types of molecules they ionize. Acid Ox (x = 1-9) and basic N1Ox (x = 0-2) classes were dominant in the wastewater DOM detected in negative-ion and positive-ion ESI mode, respectively. And the wastewater DOM contains considerable amounts of polycyclic aromatic hydrocarbons that did not respond to ESI but can be ionized selectively by APPI. Compared with riverine DOM, the refinery wastewater DOM has a higher molecular complexity and is more enriched in hydrocarbon, and nitrogen- and sulfur-containing compounds. The results show that the major components of refinery wastewater DOM were distinctive from those of the natural organic matter. Though not quantitative, the results obtained by various ionization techniques were found to be complementary, and are helpful to our understanding of the selectivity of different ionization techniques as well as the molecular compositions of DOM.

Transformation characteristics of polycyclic aromatic hydrocarbons during hydrothermal liquefaction of sewage sludge

Transformation characteristics of polycyclic aromatic hydrocarbons (PAHs) during hydrothermal liquefaction (HTL) of sewage sludge are explored in this study. PAHs are generated in the range of 7.3–13.8 mg/kg during HTL of sludge. The increase of reaction time (0–60 min) favors the formation of PAHs; however, the reaction temperature and solid–liquid ratio exhibit a critical value (300 °C and 0.1 g/mL, respectively), at which, the amounts of PAHs synthesized are the lowest. Most PAHs (> 89%) are distributed in bio-oil. Compared with those of raw sludge, the total/leachable contents and toxic equivalent quantity (TEQ) of PAHs in biochar are all reduced, suggesting a lower environmental risk for biochar in view of PAH hazard. Notably, the total contents of PAHs in bio-oil reach 55.0–106.6 mg/kg, with high TEQ values of 6.1–8.6 mg/kg. The liquefaction process should be further improved to reduce the content and toxicity of PAHs in bio-oil.

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.

Polycyclic Aromatic Hydrocarbons Formation and Mitigation in Meat and Meat Products

The phenomenon of polycyclic aromatic hydrocarbons (PAHs) in processed meats and meat products has been a serious concern to scientists in the last few decades. This study investigates PAHs formation and mitigation in processed meats and meat products. Common carcinogenic PAHs are Benzo[a]pyrene (B[a]P), Benzo[a]anthracene (B[a]A), Benzo[b]fluoranthene (B[b]FA), Benzo[ghi]perylene (B[ghi]P), and Dibenzo(a,h)anthracene (DB[a,h]A). The European Union maximum permissible level of 2.0 µg/kg (0.002 mg/kg) for BaP and 12 µg/kg (0.012 mg/kg) for the sum of 4PAHs (B[a]P + Chr + B[b]F + B[a]A) were approved by Commission Regulation (EC) No. 1881/2006 of 19 December 2006 as amended by Regulation (EU) No. 835/2011 of 19 August 2011 for B[a]P for grilled or smoked meat and fish for human consumption. PAH formation in processed meats and meat products are influenced by different cooking processes and processing techniques like roasting, barbecuing, grilling, smoking, heating, drying, baking, ohmic infrared cooking, and so on. The levels of PAHs depend on factors like distance of food from heat source, source of fuel, level of processing, cooking durations/time and techniques, or methods of cooking. Other methods and processes like conching, and storage also enhance the amount of PAHs in processed meats and meat products. To mitigate the quantity of PAHs in processed meats and meat products, standardization of processed meats and meat products and processes, designing appropriate cooking tools and methods, and developing model regulations will assist in this direction and enhance the quality and safety of processed meats and meat products.

The effect of the smoking process on polycyclic aromatic hydrocarbons contents in Hashemi and Domsiah rice cultivars

Polycyclic aromatic hydrocarbons (PAHs) are a group of lipophilic organic compounds consisting of two or more fused aromatic rings. Ingestion through contaminated food and water is a major route of human exposure to PAHs. Smoked products are important sources of dietary PAHs. Therefore, this study evaluated the effect of smoking times on the content of PAH compounds. The result showed that smoking duration had a significant effect on Benzo[a]pyrene (BaP) and 4PAH indices in both cultivars (Hashemi and Domsiah) between the three test groups (nonsmoked rice, rice smoked for 10 and 14 days) (p < .05). The level of BaP index in nonsmoked rice samples was lower than the permitted limit (1 μg/kg), but increased after smoking and exceeded the permitted limit. The 4PAH index was too high in both nonsmoked and smoked rice samples and the smoking process increased further. Finally, the smoking process had a significant direct effect on PAH compounds in Hashemi and Domsiah rice during the 14 days after smoking. Practical applications The polycyclic aromatic compounds have been identified as toxic compounds in most smoked food products such as meat, rice, and fish. The staple food of most people in the Middle East is rice, whose smoked form is mostly consumed. This source contains high amounts of polycyclic aromatic hydrocarbons. It is almost impossible to accurately measure them by traditional methods. The combination of the ultrasound-assisted extraction method and high-performance liquid chromatography with a fluorescence detection (HPLC/FLD) device can be a great help in accurately identifying these compounds in two varieties of smoked rice. Since most smoked rice workshops were traditionally built and operated, combustion conditions were usually not controlled properly and control criteria were not considered; therefore, smoked rice with high amounts of PAH compounds was produced. There is a need for replacement of the traditional smoking process with the industrial smoking process, use wood instead of paddy, revise the rice standard, and establish control limits for PAH compounds, especially for smoked rice.

Effect of Co-contamination by PAHs and Heavy Metals on Bacterial Communities of Diesel Contaminated Soils of South Shetland Islands, Antarctica.

Diesel oil is the main source of energy used in Antarctica. Since diesel is composed of toxic compounds such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals, it represents a constant threat to the organisms inhabiting this continent. In the present study, we characterized the chemical and biological parameters of diesel-exposed soils obtained from King George Island in Antarctica. Contaminated soils present PAH concentrations 1000 times higher than non-exposed soils. Some contaminated soil samples also exhibited high concentrations of cadmium and lead. A 16S metagenome analysis revealed the effect of co-contamination on bacterial communities. An increase in the relative abundance of bacteria known as PAH degraders or metal resistant was determined in co-contaminated soils. Accordingly, the soil containing higher amounts of PAHs exhibited increased dehydrogenase activity than control soils, suggesting that the microorganisms present can metabolize diesel. The inhibitory effect on soil metabolism produced by cadmium was lower in diesel-contaminated soils. Moreover, diesel-contaminated soils contain higher amounts of cultivable heterotrophic, cadmium-tolerant, and PAH-degrading bacteria than control soils. Obtained results indicate that diesel contamination at King George island has affected microbial communities, favoring the presence of microorganisms capable of utilizing PAHs as a carbon source, even in the presence of heavy metals.

Lumped Kinetics for Homogeneous Reactions of n-Hexadecane and n-Decene as Model Compounds for PE Pyrolysis Primary Tars

The focus of this paper is to establish a lumped kinetic scheme for secondary reactions of tar produced from pyrolysis of plastics or polymer-based wastes. Notably, the focus is not on the detailed yield of all reaction intermediates and products but on the propensity to form soot. Based on the assumption that that primary tar from pyrolysis of plastic wastes is mostly formed by aliphatics which can undergo progressive aromatization to polycyclic aromatic hydrocarbons (PAHs) and soot, a reaction network with 198 species and 6307 reactions proposed by Ranzi and coworkers was lumped into a very simple five reaction mechanism. The lumped kinetic model has been used to predict PAHs and soot formation in different conditions and proved to be a good alternative to comprehensive kinetic models up for relatively low temperature and short residence times (of up to 1 min at 1200 K, up to 1 s at 1400 K). At higher temperature/longer residence times, the simplified model still provides reasonable qualitative trends but the amount of PAHs and soot is underestimated. The timescale of aromatization under inert conditions appears similar for all the alkanes and alkenes examined and also the yields in main reaction products seem to scale well with the number of carbon and hydrogen atoms of the parent alkane/alkene. Evolution of the young aliphatic tar into large aromatics is prevented as long as gaseous oxygen being available for oxidation. The lumped kinetic model has been used to highlight the effect of different modes of oxygen feeding and of incomplete mixing of fuel and oxygen on the formation of PAH and soot.

On the growth of Polycyclic Aromatic Hydrocarbons (PAHs) in a coflow diffusion flame of ethylene

In the last two decades several mechanisms have been proposed for the growth of PAHs during combustion. Studies have suggested that the growth of PAHs of different structures should be analyzed carefully to improve our understanding of PAH formation during combustion. In this study, a wide of range of PAHs of different structures have been measured along the centreline of a coflow diffusion flame of ethylene using GC/MS, allowing for a previously not possible detailed analysis of potential formation routes. The discussed potential global empirical pathways can help in the development of accurate and detailed chemical mechanisms in the future. The experimental results show that the difference in reactivity of the sites of a PAH where growth takes place limits the formation of benzenoid PAHs at high temperatures. This difference in reactivity also leads to the formation of PAHs with a five-membered ring at high temperatures. The recombination of PAH radicals may not be favoured in this flame which explains the small amounts of alkyl-bridged PAHs at high temperatures. PAHs with an alkyl sidechain are favoured only along the free edge. Alkyl substituted PAHs are formed in low amounts and decrease with an increase in temperature. Methylene-bridged PAHs can lead to faster growth of large PAHs and become significant at intermediate temperatures. The target flame has also been simulated using state-of-the-art models. The simultaneous measurements of both PAHs and soot allowed for a comprehensive assessment of the chemical mechanisms and soot aerosol dynamics. The assessment suggests that both the chemical mechanisms and the soot aerosol dynamics need further improvements. The results confirm the importance of accounting for PAH structure when developing kinetic mechanisms and their coupled soot formation models. A complete database comprising of PAHs, soot and temperature is generated for future model validations.

Rapid screening and quantitation of PAHs in water and complex sample matrices by solid-phase microextraction coupled to capillary atmospheric pressure photoionization-mass spectrometry.

A capillary atmospheric pressure photoionization (cAPPI) source was used to analyze polycyclic aromatic hydrocarbons (PAHs) in complex matrices like grilled meat extract and urban dust reference material, as well as screening for PAHs in aqueous samples such as tap and lake water. A high-throughput workflow was developed that allowed rapid screening of unknown samples by direct solid-phase microextraction (SPME) coupled with cAPPI-MS, with confirmatory gas chromatography performed only for samples containing trace amounts of PAHs. Extraction times were as low as 15 s, with a total analysis time of 2 min per sample for screening. Limits of detections were in the low pg/ml range and in the subpg/ml range for the direct and chromatographic approach, respectively, with a linear dynamic range between two and three orders of magnitude, as determined for 15 model PAHs. This rapid approach represents an attractive way to screen samples containing nonpolar compounds using an ambient ionization source.