Phase Polycyclic Aromatic Hydrocarbons Research Articles

Characteristics and sources of polycyclic aromatic hydrocarbons in dew in urban ecosystems in Northeast China

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the atmospheres above major cities in Northeast China are relatively high. Dew is an effective way to settle and remove particulate and gaseous matter in the formation process. Notably, 16-PAH concentration dew analysis was conducted in four major cities (Harbin, Changchun, Shenyang and Dalian) from April to November 2023. In the study area, 2–3-ring PAHs dominated in dew in both the dissolved and particle phases, followed by 4-ring and 5–6-ring PAHs. Phe was the most common individual PAH in dew. Because PAHs in wet deposition are closely related to those in the atmosphere, the concentration of PAHs in dew was much lower than that in snow. The proportions of the gaseous-phase scavenging ratio (Wg) to the total scavenging ratio (Wt) in Harbin, Changchun, Shenyang and Dalian increased with increasing temperature, reaching 22.98%, 29.02%, 30.71% and 33.22%, respectively, which indicated that the ability of dew to remove PAHs in the particle phase was greater than that to remove PAHs in the gas phase. The concentration of dissolved-phase PAHs in dew was lower than that of particle-phase PAHs. The total PAH fluxes were 43.25, 33.35, 32.16, and 25.63 ng/m2·d in Harbin, Changchun, Shenyang and Dalian, respectively, decreasing from north to south. The dew amount was much smaller than the rainfall and snow amount (by two orders of magnitude), and the PAH flux in dew was much lower than that in rain and snow. Isomeric ratio assessment coupled with principal component analysis (PCA) indicated that the source of PAHs in dew was a combination of vehicle emissions and biomass and coal combustion. PAHs in dew mainly originated from local sources rather than from long-range atmospheric transport. This study revealed the effects of PAHs in dew on the air quality and the removal of PAHs by dew.

Polycyclic aromatic hydrocarbon and its adducts in peripheral blood: Gene and environment interaction among Chinese population

BackgroundBenzo(a)pyrene (B[a]P) is the most widely concerned polycyclic aromatic hydrocarbons (PAHs), which metabolizes benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) in vivo to produce carcinogenic effect on the body. Currently, there is limited research on the role of the variation of metabolic enzymes in this process. MethodsWe carried out a study including 752 participants, measured the concentrations of 16 kinds PAHs in both particle and gaseous phases, urinary PAHs metabolites, leukocyte BPDE-DNA adduct and serum BPDE- Albumin (BPDE-Alb) adduct, and calculated daily intake dose (DID) to assess the cumulative exposure of PAHs. We conducted single nucleotide polymorphism sites (SNPs) of metabolic enzymes, explored the exposure–response relationship between the levels of exposure and BPDE adducts using multiple linear regression models. ResultOur results indicated that an interquartile range (IQR) increase in B[a]P, PAHs, BaPeq, 1-hydroxypyrene (1-OHP), 1-hydroxynaphthalene (1-OHNap) and 2-hydroxynaphthalene (2-OHNap) were associated with 26.53 %, 24.24 %, 28.15 %, 39.15 %, 12.85 % and 14.09 % increase in leukocyte BPDE-DNA adduct (all P < 0.05). However, there was no significant correlation between exposure with serum BPDE-Alb adduct (P > 0.05). Besides, we also found the polymorphism of CYP1A1(Gly45Asp), CYP2C9 (Ile359Leu), and UGT1A1(downstream) may affect BPDE adducts level. ConclusionOur results indicated that leukocyte BPDE-DNA adduct could better reflect the exposure to PAHs. Furthermore, the polymorphism of CYP1A1, CYP2C9 and UGT1A1affected the content of BPDE adducts.

Research on Pollutant Emission Characteristics of Typical Biomass-fired Boilers

The combustion of biomass fuel boilers not only produces inorganic pollutants such as carbon oxides, nitrogen oxides, sulfur compounds, but also organic pollutants such as VOCs and PAHs, which directly affect the global biogeochemical cycle and atmospheric changes. Compared with foreign countries, there is relatively less research and related standards on the emission of organic pollutants from biomass fuel boilers in China. Therefore, it is necessary to study the emission characteristics of organic pollutants from biomass boilers, which can provide reference for the establishment of organic pollutant emission standards for biomass fuel boilers in China.The emission characteristics of volatile organic compounds(VOCs) and polycyclic aromatic hydrocarbons(PAHs) organic pollutants in the flue gas of three typical biomass-fired boilers in Chongqing were studied, and the emission concentrations of particulate matter, sulfur dioxides(SO2), and nitrogen oxides(NOX) were measured.The results show that the sulfur dioxide emissions from the three types of biomass-fired boilersrs are lower than the local standards in Chongqing, while nitrogen oxides and particulate matter have a phenomenon of exceeding the emission limits of the local standards in Chongqing. The main components of VOCs emitted from biomass powder and biomass particle combustion are OVOCs and aromatic hydrocarbons, while the main components of VOCs emitted from wood biomass combustion are alkynes. The gas-solid distribution pattern of PAHs during the combustion of three types of biomass is basically consistent. Low ring PAHs are mainly enriched in the gas phase, while medium and high ring PAHs are mainly enriched in particulate matter.

Characteristics of the pyrolytic products and the pollutant emissions at different operating stages from a pilot waste tire pyrolysis furnace

Pyrolysis is considered a highly practical, cost-effective, and environment-friendly technology for waste tires disposal. In this study, pyrolysis processes of waste tires were conducted in a pilot scale furnace feeding at 30 kg/h. The properties of pyrolytic products and the distribution patterns of pollutants generated in different operating stages (start-up, steady, and shut-down) were investigated. The pyrolytic gas in the steady state had a high caloric value of 10799 kJ/Nm3, valuable as heating source for pyrolysis. The elements of sulfur and zinc were effectively fixed as ZnS in the pyrolytic carbon. The basic properties of pyrolytic oil were in line with commercial diesel oil except for the lower flash point. Heavy metals were mainly concentrated in the pyrolytic carbon, with slightly higher concentrations in the steady state. Moreover, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were mainly concentrated in the pyrolytic oil, with predominated low-ring PAHs and high chlorinated PCDD/Fs. The concentrations of PAHs and PCDD/Fs in the gas phase were higher during the start-up stage due to the memory effect, whereas were effectively reduced during the steady stage. The concentration of PAHs in the solid phase was highest during the furnace start-up and lowest in the shut-down stage. In contrast to PAHs, the PCDD/Fs in the solid phase reached their highest concentration during the shut-down stage, which was mainly affected by temperature. The results provide guidance for the reducing of pollutant emissions and the recycling of pyrolytic products.

Investigations into the transition to sustainable alternative fuels in a South African underground platinum mine

Adverse environmental impacts associated with the use of fossil fuels and the over-dependence thereon has made energy security and sustainability a critical issue worldwide particularly for key energy intensive economic sectors which are heavily dependent on diesel. We thus investigated the feasibility of a transition to two different alternative fuels namely, rapeseed methyl ester (RME) biodiesel and gas-to-liquid fuel (GTL), in the platinum mining industry in South Africa. Load haul dump vehicles are the most abundant workhorses underground and were the selected vehicles to test alternative fuels at 100% without any engine modification. Potential reduction of harmful unregulated polycyclic aromatic hydrocarbon (PAH) emissions was the focus of the research due to their adverse impacts on the environment, human health and engine operations. Quantitative collection of gas and particle phase PAHs was made possible using portable denuder devices followed by analysis by two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Results showed that total PAH emissions from a high idling vehicle decreased dramatically when diesel was substituted with both biofuels (total gas phase PAH concentrations of 34; 14 and 9 µg m-3 for diesel, GTL and RME, respectively) and no substantial hinderance on engine performance was reported. This novel sector specific study on unmodified heavy duty working vehicles can potentially translate into a real-world, immediate solution, as not only would the selected biofuels be able to directly replace diesel, but both have high potential of being locally produced in South Africa and assist in the promotion of a circular economy.

128 Exposure to soot, Measured as Black Carbon and PAH, in Swedish Chimney Sweeps

Abstract The overall aim of our research is to study chimney sweeps exposure to soot to be able to give recommendations on how to effectively reduce the exposure. To do this a suitable method to study soot exposure is required. In this study we use a new method to study the personal airborne exposure to soot measured as black carbon (BC). BC is measured with a AethLabs MA200 micro aethalometer with a flow rate of 100 mL/min and sampling time of 1 min. By using a direct-reading instrument we aim to identify variability in exposure levels during the workday, and potential work tasks contributing to elevated exposure to soot. The study includes 20 chimney sweeps performing black sweeping in Sweden and BC is measured for eight workdays for each individual. During these days individuals also fill out a diary of work tasks performed. To assess the value of the BC levels, airborne polycyclic aromatic hydrocarbon (PAH) is also measured with personal sampler for particulate- and gas phase PAH. PAH is measured in parallel with BC during one workday. Preliminary results show variability of BC levels between different individuals as well as different workdays for the same individual. We are also able to link BC levels with work tasks from the diaries. Significantly elevated PAH levels and especially the particle-bound PAHs, including the carcinogenic benzo(a)pyrene, were observed in most samples.

Deposition of atmospheric polycyclic aromatic hydrocarbons in rural areas: Current data and historical record from an ombrotrophic peatland

Atmospheric concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) were measured in a rural area in northern Spain. Both the gas phase and particulate fraction were determined to evaluate the types and abundance of PAHs taken up by vegetation and the historical record of PAH deposition in an ombrotrophic peatland over the last 300 years. The total atmospheric PAH concentration was ca. 2.5 ng m−3, a value that is slightly lower value than those found in other rural areas, consistent with those of remote areas (Pyrenees, Alps, and Caledonian Mountains), and much lower than those recorded in urban areas. The particulate fraction showed a greater content of high molecular weight PAHs, whereas the gas phase was enriched in low molecular weight homologues. The concentration of total PAHs in the gas phase was higher than that in the particulate fraction (ca. 80%) and similar to that found in other localities in remote areas. PAHs showed seasonal variability. In this regard, the highest concentrations in the gas phase occurred in winter and autumn, whereas in the particulate fraction they were found in winter and spring. Of note, the concentrations of PAHs increased in the particulate fraction during the years in which fires occurred. The PAH content in peat-forming plants in this area showed a similar distribution to that of the gas phase. The historical record of the depositional fluxes of PAHs in an ombrotrophic peatland in the study area, which was dated radiometrically, allowed to reconstruct the changes in pollutant content between 1775 and the present. In general, the PAHs detected were of pyrogenic origin (fossil fuels and wood combustion). The concentrations of these pollutants increased from uniform background levels at the turn of the second half of the 19th century, which were linked to industrial development, to maximum values during the first half of the 20th century until the beginning of the 21st century, when the extraction and combustion of coal was extensive close to the study area. In contrast, in the uppermost part of the record, PAH concentrations decreased. This reduction is attributed to the implementation of environmental policies, although the concentrations of these pollutants were still greater than during the preindustrial period. To gain a detailed understanding of the deposition and evolution of PAHs in the study area, here it is reported on a new method that integrates current atmospheric data on PAHs with information on their accumulation in plants and the historical peat record of a rural area in Spain. The methodology described herein could be applied to other scenarios in the context of PAH pollution.

Elevated nitrate promoted photodegradation of PAHs in aqueous phase: Implications for the increased nutrient discharge.

Polycyclic aromatic hydrocarbons (PAHs) are frequently released in aqueous phase by oil spill or from other sources, and photochemical oxidation is one of their major weathering processes. In this study, the photochemical behavior of phenanthrene (PHE, as a representative PAH) were studied and the effects of nitrogenous compounds were evaluated. The results showed that nitrate was an effective photosensitizer for improving the photodegradation of PHE, but the promoting effect was less effective in seawater due to the presence of halogen ions; the ammonia played a negligible role on PHE degradation. The photochemical ionization was a key process for PHE degradation, it can be retarded due to the quenching of triplet excited state by dissolved oxygen, and the inhibition was most prominent in fresh water. The presence of nitrate increased the steady state concentration of •OH from 2.08×10-15 M to 1.04×10-14 M in fresh water, and from 1.5×10-16 M to 2.08×10-15 M in seawater. The secondary-order reaction rate constant between PHE and •OH (k•OH,PHE) was determined as 5.70 × 109 M-1 s-1. Similar trend was observed for 1O2. The contribution of •OH to PHE removal was more prominent in fresh water than in seawater due to the quenching effects of halogen, and the increasing of nitrate enlarged the contribution of •OH. Two possible PHE degradation pathways were proposed based on GC-MS analysis and DFT calculation. The Quantitative Structure-activity Relationship (QSAR) evaluation showed that some degradation intermediates were more toxic than PHE, but the total environmental risk was still diminished due to the low percentage of toxic intermediates. This study provided theoretical and experimental insights into the influence of nitrogenous compounds on the photodegradation of PHAs in water environment.

Emission factors for polycyclic aromatic hydrocarbons from laboratory biomass-burning and their chemical transformations during aging in an oxidation flow reactor

Atmospheric polycyclic aromatic hydrocarbons (PAHs) can be emitted from different combustion sources including domestic biomass burning, internal combustion engines, and biomass burning (BB) in wild, prescribed, and agricultural fires. With climate warming and consequent global increases in frequency and severity of wildfires, BB is a dominant source of PAHs emitted into the atmosphere.In this study, six globally and regionally important and representative fuels (Alaskan peat, Moscow peat, Pskov peat, eucalyptus, Malaysian peat, and Malaysian agricultural peat) were burned under controlled conditions in the combustion chamber facility at the Desert Research Institute (DRI, Reno, NV, USA). Gas- and particle-phase BB emissions were aged in an oxidation flow reactor (OFR) to mimic five to sevendays of atmospheric aging. To sample gas- and particle-phase BB emissions, fresh and OFR-aged biomass-burning aerosols were collected on Teflon-impregnated glass fiber filters (TIGF) in tandem with XAD resin media for organic carbon speciation. The objectives of this study were to i) quantify the emission factors for 113 PAHs emitted from the combustion of the six selected fuels, ii) characterize the distribution of PAH compounds between gas and particle phases for these fuels, iii) identify the changes in PAHs during OFR-aging, and iv) evaluate toxicity potential with characterized compounds.We found that combustion emissions of gas-phase PAHs were more abundant (>80 % by mass) than particle-phase PAHs, for emissions from all combusted fuels. The mass fraction of substituted napthalenes in Moscow peat and Malaysian peat emissions were ∼70 % & 84 %, respectively, whereas in Eucalyptus the same fraction was <50 %, which indicates that these substituted compounds can be used as tracers for peat emissions. Mass concentrations of gas- and particle-phase PAHs were reduced by ∼70 % after OFR oxidation. However, the understanding of the fate of PAHs during OFR oxidation requires further investigations. Our results also indicate that the PAH toxicity of BB samples would be underestimated by 10–100 times if only the BaPeq for the 16 US EPA priority PAHs in the particle phase are included.

Gas Particle Partitioning of PAHs Emissions from Typical Solid Fuel Combustions as Well as Their Health Risk Assessment in Rural Guanzhong Plain, China.

Air pollutants from the incomplete combustion of rural solid fuels are seriously harmful to both air quality and human health. To quantify the health effects of different fuel-stove combinations, gas and particle partitioning of twenty-nine species of polycyclic aromatic hydrocarbons (PAHs) emitted from seven fuel-stove combinations were examined in this study, and the benzo (a) pyrene toxicity equivalent (BaPeq) and cancer risks were estimated accordingly. The results showed that the gas phase PAHs (accounting for 68-78% of the total PAHs) had higher emission factors (EFs) than particulate ones. For all combustion combinations, pPAHs accounted for the highest proportion (84.5% to 99.3%) in both the gas and particulate phases, followed by aPAHs (0.63-14.7%), while the proportions of nPAHs and oPAHs were much lower (2-4 orders of magnitude) than pPAHs. For BaPeq, particulate phase PAHs dominated the BaPeq rather than gas ones, which may be due to the greater abundance of 5-ring particle PAHs. Gas and particle pPAHs were both predominant in the BaPeq, with proportions of 95.2-98.6% for all combustion combinations. Cancer risk results showed a descending order of bituminous coal combustion (0.003-0.05), biomass burning (0.002-0.01), and clean briquette coal combustion (10-5-0.001), indicating that local residents caused a severe health threat by solid fuel combustion (the threshold: 10-4). The results also highlighted that clean briquette coal could reduce cancer risks by 1-2 orders of magnitude compared to bulk coal and biomass. For oPAH, BcdPQ (6H-benzo(c,d)pyrene-6-one) had the highest cancer risk, ranging from 4.83 × 10-5 to 2.45 × 10-4, which were even higher than the total of aPAHs and nPAHs. The dramatically high toxicity and cancer risk of PAHs from solid fuel combustion strengthened the necessity and urgency of clean heating innovation in Guanzhong Plain and in similar places.

Computational Studies on the Reactivity of Polycyclic Aromatic Hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment as toxic pollutants. In this study, quantum chemistry methods are used to study reactions of PAHs in both particle and gas phases. Seven theoretical methods are exploited to predict the reactive sites of 15 PAHs in the particle phase. Among these methods, the performance of the condensed Fukui function (CFF) is optimum. The gas-phase reactions of eight PAHs are also investigated. Except for fluorene, CFF predicts correctly the gas-phase mono-nitro products for seven systems. The products of fluorene predicted by CFF are 1-nitrofluorene and 3-nitrofluorene, which is however inconsistent with the experimental results. Transition state theory is then used to investigate the reaction mechanism of fluorene. Calculated rate constants for 3-nitrofluorene and 2-nitrofluorene formation are much bigger than that for 1-nitrofluorene formation, which is in agreement with the experimental results.

Compositional and seasonal differences of gas and particle phase polycyclic aromatic hydrocarbons (PAHs) over the southern Baltic Sea coast

In this study, 16 USEPA-prioritized PAHs in gas- and particle-phase (PAHg+p), associated chemical and meteorological parameters, and backward trajectory simulations were explored in a coastal city in Poland, between April 2019 and May 2020. This study reports several important aspects of PAHg+p, i.e. variation, composition, distribution profiles, impact of weather conditions, and correlation analysis between target PAH compounds and influencing inorganic gaseous pollutants. Specifically, higher and more variable concentrations of total PAHg+p (mean ± SD, ng m−3) were observed during winter (36.38 ± 24.19) compared to autumn (22.3 ± 17.44), summer (21.52 ± 13.30) and spring (19.90 ± 13.13). A distribution profile of parent PAHg+p was as follows: 3-ring > 4-ring > 2-ring > 5-ring > 6-ring, although their relative contribution to the total PAHs showed statistically significant differences between seasons (p < 0.05). Precipitation-driven loss of ΣPAHg+p was lower in the warm period than in the cold one, reflecting higher PAH concentrations in winter. A seasonal model-based analysis of incremental lifetime cancer risk showed a higher potential cancer risk for children than those for adult females and males. The adverse health impacts associated with PAH exposure via inhalation route indicate the need for implementation of pollution-control policies in this region.

Evaluation of Mass Spectrometric Methods for Screening Polycyclic Aromatic Hydrocarbons in the Particulate Phase of Wildfire/Biomass Smoke.

Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds containing multiple aromatic rings formed during incomplete combustion. Since many of them are known mutagens and carcinogens, PAHs found in the particulate matter (PM) from the wildfire smoke may pose significant health risks to the wildland firefighters. It is pivotal to determine the levels of PAHs in the PM to evaluate the health effects of their inhalation exposure. However, the determination of PAHs using the conventional chromatographic approaches is often time-consuming and laborious. Herein, we describe a novel method for screening nonpolar and polar PAHs in the PM of smoke by direct analysis in real-time mass spectrometry (DART-MS). PM2.5 and PM10 samples were collected on the quartz filters with a sampling system consisting of a cascade impactor with a portable sampling pump. Various indoor and outdoor experiments from biomass burns were conducted to evaluate the PM sampling systems. PAHs were analyzed by DART-MS and gas chromatography-mass spectrometry (GC-MS) methods. The PM samples were collected in California during the wildfire season of fall 2020, and significant levels of multiple nonpolar PAHs and polar PAHs were detected. Overall, the DART-MS method has shown promising ability for high-throughput screening of PAHs in the PM of smoke. Further studies are currently under way to apply this method to study the particulate phase PAH exposures of wildland firefighters during their firefighting activities.

Evolution of PAHs in the mobile phase of low-rank coal during medium–low-temperature pyrolysis

The generation and release of polycyclic aromatic hydrocarbons (PAHs) during coal pyrolysis have been extensively studied, yet the evolution process of PAHs in the mobile phase is poorly understood. In this study, Yulin (YL) subbituminous coal and its solid products (YL350–700) obtained by pyrolysis at ∼350–700 °C were treated with dichloromethane, and the extracted PAHs were analyzed by gas chromatography and mass spectrometry. The total PAH concentration in the YL350–700 mobile phase was found to increase and then decrease with increasing pyrolysis temperature, and peak in the YL380 sample. The concentrations of alkylated PAHs were found to be the main contributors to the total PAH concentrations among the YL350–700 samples. YL coal was dominated by 4-ring PAHs, while YL350–700 samples were all dominated by 2-ring PAHs (naphthalene and alkylated naphthalenes). Variations in the proportion of 2-ring PAHs and the degree of naphthalene alkylation in YL350–700 indicated that alkylated naphthalenes were the main component of PAHs generated during YL coal pyrolysis at medium–low temperatures. This may suggest that the condensed aromatic units in the macromolecular structure of YL coal mainly consist of low-ring PAHs. Finally, an evolutionary process for PAHs in the mobile phase of YL subbituminous coal during pyrolysis at medium–low temperatures was proposed.

Effects of fuel injection system and exhaust gas catalytic treatments on PAH emissions from motorcycles.

The motorcycles are unignorable near-ground pollutant emission sources that increase the human exposure in the dense area. However, the information of the polycyclic aromatic hydrocarbons (PAHs) emissions under different scenarios of engine and emission control for motorcycle is limited. This study focused on the PAH emissions from two fuel-injection types of motorcycles, including the premixed fuel-injection (PFi) with carburetor and electronic fuel-injection (EFi). Specifically, the effects of throttle opening (TO), secondary air system (SAS), oxygen sensor (OS), oxidation catalytic converter (OCC), and three-way catalytic converter (TWC) on PAH emissions are investigated. Results show that the PAH emission concentrations increase 227-727%, 351-492%, and 155-408% by the increasing TO ratio, unworking SAS, and OS units in both motorcycles. For the PFi engine, the OCC unit is found to be more effective in PAH control (31-89%) than the SAS system (72-80%), especially under low TO operation. For the EFi engine which dominates the motorcycle market recently, the oxygen sensor for more accurate combustion control shows a better PAH reduction (36-76%) than TWC system (21-66%). The ultra-fine particulate phase PAHs, which is hardly removed by catalyst, needs to be further considered. Moreover, the total PAH emission level of the EFi engine is still about ten times higher than that of the PFi. By the annual emission calculation for three densely populated countries, the recent evolution significantly reduces the annual hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) emissions but have unignorable PAH emissions. These emissions continuously affect the human health in the near-ground urban air and need to be considered in the next generation of motorcycle design.

Study on the variations of extractable polycyclic aromatic hydrocarbons in lignite and semi-coke

Low-temperature pyrolysis is one of the most important technologies for the clean and efficient utilization of lignite. Semi-coke, the solid product of this process, has been widely used as both an industrial and household clean fuel. In this study, three lignites from China (EE), Indonesia (YN), and Mongolia (WM) and their semi-cokes obtained through pyrolysis at 550 °C were treated with dichloromethane, and the extracted polycyclic aromatic hydrocarbons (PAHs) were analyzed using a gas chromatograph/mass spectrometer. The results showed that the total concentrations of PAHs in EE, YN, and WM were 125000, 4400, and 5800 ng/g, respectively, and those in their semi-cokes were 4700, 10000, and 5500 ng/g, respectively. The concentrations of alkylated PAHs (aPAHs) were higher than those of parent 16 US EPA priority PAHs (16 PAHs) in lignites, while parent 16 PAHs were more abundant in semi-cokes. Both lignites and semi-cokes were dominated by 2-ring PAHs (naphthalene and alkylated naphthalenes), followed by 3- and 4-ring PAHs. The proportion of 2-ring PAHs in the semi-cokes increased with respect to that in the lignites, and the degree of alkylation of the PAHs decreased. This suggested that the extractable PAHs changed to smaller parent PAHs during the low-temperature pyrolysis. The concentration and composition of PAHs in the mobile phase of the semi-coke are an important part of its structural characteristics and are closely related to the macromolecular structure of raw coal. Thus, this study on PAHs in semi-coke provides relevant information on the structural evolution of coal during pyrolysis and further improves our understanding of clean fuel.

Gas-particle partitioning of polycyclic aromatic hydrocarbons from oil combustion involving condensate, diesel and heavy oil

This study focuses on the gas-particle (G-P) partitioning of 16 polycyclic aromatic hydrocarbons (PAHs) from oil combustion, which is one of the important contributors of anthropogenic PAHs but has been rarely studied. The combustions of different types of oils involving ultra-light to heavy oils were investigated, and the PAH partitioning mechanism was determined by the widely used Junge-Pankow adsorption model, Koa absorption model, and dual sorption model, respectively. The results show that the source-specific diagnostic ratios of Ant/(Ant+Phe) are between 0.09 and 0.24, the estimated regression slopes of G-P partition coefficients (KP) of the total PAHs on their sub-cooled liquid vapor pressures (PLO) are in the range of − 0.34 to − 0.25, and the predicted fractions of PAHs in the particle phase (φ) by Koa absorption model are close to the measured values, while the log KPvalues of the LMW PAHs from the combustions of diesel and heavy oil are better represented by the dual sorption model. Our findings indicate that PAHs are derived from mixed sources that include the unburned original oil and combustion products, and the PAH partitioning mechanism is governed by the process of absorption into organic matter because of the unburned oil, but both adsorption and absorption exist simultaneously in the lighter PAHs from the combustions of heavier oils (i.e., diesel and heavy oil). Based on these findings, the understanding of the fate and transport of PAH emissions and the optimization of the emergency responses to accidents such as marine oil spills would be potentially improved.

Occurrence and ecological risks of PAHs in the dissolved and particulate phases of coastal surface water of Taiwan

Surface seawater were collected from seven sites along the coast of Taiwan. A total of 100 L seawater was pre-concentrated from each site and the concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the dissolved and particulate phases were analyzed. The characteristics, potential sources, and ecological risks of PAHs in seawater were assessed. The concentration of total PAHs (TPAHs) in the dissolved phases ranged between 3.3–25.8 ng/L, with an average of 14.7 ± 8.9 ng/L, classified as slightly contaminated, while the particulate phase ranged between 3.3–22.4 ng/L (8.5 ± 6.8 ng/L). The TPAHs concentrations in seawater are mainly dominated in the dissolved phase (60.4 ± 22.0%). The partition coefficients of PAHs in the particulate and dissolved phases were linearly correlated significantly with octanol–water partition coefficient (r = 0.744; p<0.01), indicating that hydrophobicity plays a key role in the partitioning behavior of PAHs. The dissolved phase PAHs in seawater were dominated by 3-ring PAHs (84.8 ± 3.9%), while the particulate phase was dominated by 5-ring PAHs (88.4 ± 9.1%). According to the diagnostic ratio, coal and biomass combustion are the main sources of PAHs, while petroleum and petroleum combustion sources also contributed to the northeast coast. The results of toxic equivalence quotients and mean risk quotient showed that the toxicity and risks of PAHs in the particulate phases were higher than those in the dissolved phases. Furthermore, the proportion of 5-ring PAHs in the dissolved phase was low (5.9 ± 4.3%), but relatively contributed high potential toxicity.

Analysis of gaseous polycyclic aromatic hydrocarbon emissions from cooking devices in selected rural and urban kitchens in Bomet and Narok counties of Kenya.

Traditional combustion devices and fuels such as charcoal, wood and biomass, are widely utilised in rural and urban households in Africa. Incomplete combustion can generate air pollutants which are of human toxicological importance, including polycyclic aromatic hydrocarbons (PAHs). In this study, portable multi-channel polydimethylsiloxane rubber traps were used to sample gas phase emissions from cooking devices used in urban and rural households in Bomet and Narok counties of Kenya. A wide range of total PAH concentrations was found in samples collected (0.82 - 173.69 µg/m3), which could be attributed to the differences in fuel type, combustion device, climate, and nature of households. Wood combustion using the 3-stone device had the highest average total PAH concentration of ~71 µg/m3. Narok had higher indoor total gas phase PAH concentrations averaging 35.88 µg/m3 in urban and 70.84 µg/m3 in rural households, compared to Bomet county (2.91 µg/m3 in urban and 9.09 µg/m3 in rural households). Ambient total gas phase PAH concentrations were more similar (Narok: 1.26 - 6.28 µg/m3 and Bomet: 2.44 - 6.30 µg/m3). Although the 3-stone device and burning of wood accounted for higher PAH emissions, the charcoal burning jiko stove produced the highest toxic equivalence quotient. Monitoring of PAHs emitted by these cooking devices and fuels is critical to public health and sustainable pollution mitigation.

Non-equilibrium influence on G/P partitioning of PAHs: Evidence from the diurnal and nocturnal variation

Gas/particle (G/P) partitioning is an important behavior for the atmospheric transport of polycyclic aromatic hydrocarbons (PAHs). In this study, paired daytime and nighttime air samples were collected for one year in order to study the diurnal and nocturnal variations of concentration and G/P partitioning of PAHs. Higher PAHs concentrations in total phase were observed in nighttime. The geomean (GM) concentrations of Σ15PAHs in total phase were 69.6 and 52.8 ng/m3 in nighttime and daytime, respectively. More obviously diurnal and nocturnal variations were observed in non-heating season, with the GM ratios of Σ15PAHs in nighttime to daytime of 1.65 and 1.06 in non-heating season and heating season, respectively. The results could be attributed to emission sources and meteorological conditions. The values of particulate phase fraction (ϕP) and G/P partitioning quotient (log KP) were used to quantify the phase distribution of PAHs. For most high molecular weight PAHs, the values of ϕP and log KP in nighttime were higher than those in daytime, which could be mainly attributed to the lower temperature in nighttime. However, for the three light molecular weight PAHs (Acy, Ace and Flu), higher values of ϕP and log KP were observed in daytime. The regression of log KP against log KOA for the three PAHs in daytime differed from those in nighttime. The chemical losses of PAHs in different phases might be responsible for the result. These findings suggested that the chemical loss of PAHs in gas phase should be considered for the G/P partitioning process.