Parent, alkylated, oxygenated and nitro polycyclic aromatic hydrocarbons from raw coal chunks and clean coal combustion: Emission factors, source profiles, and health risks

Bioaccumulation, sources and health risk assessment of polycyclic aromatic hydrocarbons in Lilium davidii var. unicolor

Dietary uptake is the main pathway of exposure to polycyclic aromatic hydrocarbons (PAHs). However, there is no data regarding the pollution and health risks posed by PAHs in Lilium davidii var. unicolor. We measured the concentrations of 16 PAHs in lily bulbs from Lanzhou; analyzed the bioaccumulation, sources, and pollution pathways of PAHs; assessed the influence of baking on PAH pollution in the bulb; and assessed the cancer risks associated with PAH exposure via lily consumption. The total PAH concentrations in raw bulbs were 30.39-206.55 μg kg-1. The bioconcentration factors of total PAHs ranged widely from 0.92 to 5.71, with a median value of 2.25. Pearson correlation analysis revealed that the octanol-water partition coefficients and water solubility values played important roles in the bioaccumulation of naphthalene, fluorene, phenanthrene, pyrene, and fluoranthene in the raw bulb by influencing PAH availability in soil. Correlation analysis and principal component analysis with multivariate linear regression indicated that biomass and wood burning, coal combustion, diesel combustion, and petroleum leakage were the major sources of PAHs in the raw bulbs. The paired t-test showed that the PAH concentrations in the baked bulbs were higher than those in the raw bulbs. PAH compositions in lily bulb changed during the baking process. Baked bulbs exhibited a higher cancer risk than raw bulbs. Local adults had low carcinogenic risks from consuming lily bulbs. This study fills the knowledge gap about PAH pollution and the related health risks of PAHs in the Lanzhou lily.

Hourly emission amounts and concentration of water-soluble ions in primary particles from residential coal burning in rural northern China

Residential coal burning (RCB) stands as an important contributor to ambient pollutants in China. For the effective execution of air pollution control policies, it is essential to maintain precise emission inventories of RCB. The absence of hourly emission factors (EFs) combined with the inaccuracies in the spatial-temporal distribution of activity data, constrained the quality of residential coal combustion emission inventories, thereby impeding the estimation of air pollutant emissions. This study revised the hourly EFs for PM2.5 and water-soluble ions (WSIs) emitted from RCB in China. The hourly emission inventories for PM2.5 and WSIs derived from RCB illustrate the diurnal fluctuations in emission patterns. This study found that the emissions of PM2.5, NH4+, Cl-, and SO42- showed similar emission features with emission of 106.8 Gg, 1417.6, 356.8, and 5868.5 ton in erupt period. The results provide basic data for evaluating RCB emission reduction policies, simulating particles, and preventing air pollution in both sub-regions and time periods. The spatial emission and simulated concentration distribution of PM2.5 and WSIs indicated that emission hotspot shifted from North China Plain (NCP) to Northeast region in China. The emissions in China were well-controlled in '2 + 26' region (R28) priority region, with hotspots decreasing by 99.6% in BTH region. The RCB became the dominant contributor to ambient PM2.5 with a ratio in the range of 16.2-23.7% in non-priority region.

Characterization and health risk assessment of PM2.5-bound polycyclic aromatic hydrocarbons in Yangon and Mandalay of Myanmar

To better understand the potential adverse health effects of atmospheric fine particles in the Southeast Asian developing countries, PM2.5 samples were collected at two urban sites in Yangon and Mandalay, representing coastal and inland cities in Myanmar, in winter and summer during 2016 and 2017. The concentrations of 21 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were determined using a gas chromatography-mass spectrometry (GC-MS). The concentrations of PAHs in PM2.5 in Yangon and Mandalay ranged from 7.6 to 180 ng m-3, with an average of 72 ng m-3. The PAHs were significantly higher in winter than in summer, and significantly higher in Mandalay than in Yangon. The health risk analysis of PAHs, based on the toxic equivalent quantity (TEQ) calculation, and the incremental lifetime cancer risk (ILCR) assessment indicated that PM2.5 in Myanmar has significant health risks with higher health risks in Mandalay compared to Yangon. Diagnostic ratios of PAHs, correlation of PAHs with other species in PM2.5 and the positive matrix factorization (PMF) analysis showed that TEQ is strongly affected by biomass burning and vehicular emissions in Myanmar. Additionally, it was found that the aging degree of aerosols and air mass trajectories had great influences on the concentration and composition of PAHs in PM2.5 in Myanmar, thereby affecting the toxicity of PM2.5.

Potential toxic components in size-resolved particles and gas from residential combustion: Emission factor and health risk

Particulate matter (PM) from residential combustion is an existential threat to human health. Emission factors (EFs) of multiple potential toxic components (PTCs) in size-resolved PM and gas from eight residential fuel combustion were measured, and size distribution, gas/particle partitioning and health risks of the PTCs were investigated. Average EFs from clean coal and anthracite coal were PTEs (sum of EFs of 11 Potential Toxic Elements, 6.62 mg/kg fuels) > PAHs (sum of 22 Polycyclic Aromatic Hydrocarbons, 1.12 mg/kg) > OPAHs (sum of 5 Oxygenated Polycyclic Aromatic Hydrocarbons, 0.45 mg/kg) > PAEs (sum of 6 Phthalate Esters, 0.11 mg/kg) > NPAHs (sum of 14 Nitropolycyclic Aromatic Hydrocarbons, 16.84 μg/kg) > OPEs (sum of 7 Organophosphate Esters, 7.57 μg/kg) > PCBs (sum of 6 Polychorinated Biphenyls, 0.07 μg/kg), which were 2-3 and 1-2 orders of magnitude lower than the EFs of PTCs (except PTEs) from bituminous coal and biomass. Most PAHs, OPAHs and NPAHs, which may mainly originate from chemical reactions, showed similar size distributions and averagely 85 % concentrated in PM1. PTEs, PAEs, OPEs and PCBs generated from the release from raw fuels may have a higher proportion, so their size distributions were more complex and varied with combustion temperature, volatility of compounds, binding mode of the raw fuels, and so on. In addition, clean coal and high-quality anthracite coal could reduce the health risks from the potential organic toxic components, but also reveal the stumbling block of PTEs in risk control.

Polycyclic aromatic hydrocarbons (PAHs) in coal preparation plant products: A contributor to environmental pollution

Coal and coal gangue are petrogenic sources of polycyclic aromatic hydrocarbons (PAHs), which cause adverse impacts on the environment. Raw coal, cleaned coal, slime, slack gangue, and lump gangue from the Pingshuo No. 1 Coal Preparation Plant, China, were analyzed to determine the concentrations and compositions of 16 priority parent PAHs (16PAHs) and their alkylated derivatives (aPAHs). The ∑16PAH and ∑aPAH concentrations in the samples ranged from 18.7 to 139.2 mg/kg and 22.2 to 262.3 mg/kg, respectively, and ranked as follows: cleaned coal > raw coal > slime > lump gangue > slack gangue. Coal gangues had a higher proportion and lower degree of alkylation of 4-6-ring PAHs than coals. A summary analysis of references related to coal and coal gangue diagnostic ratios showed that their ratios could not be used to differentiate them from other PAH sources, indicating that the release of particulate coal and coal gangue would increase the uncertainty of environmental PAH identification results. The diagnostic ratios of coal gangue were relatively concentrated, and comparing the ratio distribution could reveal the coal gangue source PAHs. The toxicity risk of slack gangue was higher than that of lump gangue based on the benzo[a]pyrene-equivalent concentration; hence, more attention should be given to its escape to the environment.

The seasonal change of PAHs in Svalbard surface snow

The Arctic region is threatened by contamination deriving from both long-range pollution and local human activities. Polycyclic Aromatic Hydrocarbons (PAHs) are environmental tracers of emission, transport and deposition processes. A first campaign has been conducted at Ny-Ålesund, Svalbard, from October 2018 to May 2019, monitoring weekly concentrations of PAHs in Arctic surface snow. The trend of the 16 high priority PAH compounds showed that long-range inputs occurred mainly in the winter, with concentrations ranging from 0.8 ng L-1 to 37 ng L-1. In contrast to this, the most abundant analyte retene, showed an opposite seasonal trend with highest values in autumn and late spring (up to 97 ng L-1), while in winter this compound remained below 3 ng L-1. This is most likely due to local contributions from outcropping coal deposits and stockpiles. Our results show a general agreement with the atmospheric signal, although significant skews can be attributed to post-depositional processes, wind erosion, melting episodes and redistribution.

Insight into personal exposure characteristics and health effects of PM2.5 and PM0.25-bound PAHs and their derivatives with different heating ways in the Fenwei Plain, China

Personal exposure (PE) to polycyclic aromatic hydrocarbons (PAHs) and their derivatives in particulate matter with two aerodynamic sizes of 2.5 and 0.25 μm (PM2.5 and PM0.25) from rural housewives was studied in the Fenwei Plain, China. A total of 15 households were divided into five different groups based on the type of solid fuel and heating device used, including biomass briquette-furnace (BBF), biomass-elevated Kang (BEK), outdoor lump coal-boiler (OLC), indoor briquette coal-stove (IBC), and electricity (ELE). The PE concentrations of the PAHs and biomarkers in urine collected from the participants were determined. The results showed that the PE concentrations of total quantified PAHs in the biomass group (i.e., BBF and BEK) were 2.2 and 2.0 times higher than those in the coal groups (i.e., OLC and IBC) in PM2.5 and PM0.25, respectively. The housewives who used biomass as fuel suffered from higher potential health impacts than the coal fuel users. The incremental lifetime cancer risk for the PAHs in PM2.5 in the BBF and BEK groups exceeded the international safety threshold. Furthermore, the PE concentrations of oxygenated PAH (o-PAHs) in PM2.5 and PM0.25 in the biomass groups and the nitrated PAHs (n-PAHs) in PM0.25 in the coal groups showed strong correlations with the biomarkers. The results of this study proved the associations between exposure to the different classes of PAHs and health hazards. The findings could also serve as a guideline in establishing efficient measures for using solid fuels for cooking and household warming in northern China.

Determination of carbonyls and size-segregated polycyclic aromatic hydrocarbons, and their nitro and alkyl analogs in emissions from diesel-biodiesel-ethanol blends

This study characterizes carbonyls (RCHO), polycyclic aromatic hydrocarbons (PAHs), their nitrated (nitro-PAHs) and alkylated (alkyl-PAHs) in particulate matter in the exhaust emissions of a diesel engine. The measurements were made with a standard engine, often found in vans used in Brazil, fueled with pure commercial diesel and mixtures of 10, 20, and 30% biodiesel with 2, 4, and 6% of ethanol. Particulate matter sampling was carried out with a 10-stage cascade impactor. Chemical analyses for PAHs and their derivatives were conducted using gas phase chromatography-mass spectrometry (GC/MS). RCHO were sampled using impingers with 2,4-DNPH and analyzed using HPLC with UV detection. The results showed that emissions of all the PAHs and their derivatives were reduced with the use of biodiesel and ethanol, with the exception of the blend of 30% biodiesel with 4% ethanol. However, all the RCHO emissions increased with biodiesel and ethanol. High correlations were observed between the emissions of PAHs, alkyl-PAHs and nitro-PAHs, which suggests a similarity in the formation mechanisms of these compounds. All PAHs' emissions have a strong negative correlation with biodiesel content and with RCHO emissions and a medium correlation with ethanol content. In contrast, biodiesel and ethanol with the RCHO emissions lead to a positive correlation coefficient of these compounds which is more pronounced for biodiesel than ethanol.

Spatial distribution, source identification, and human health risk assessment of PAHs and their derivatives in soils nearby the coke plants

The coking industry can generate large amounts of polycyclic aromatic hydrocarbons (PAHs) and their derivatives, which may negatively impact the environment and human health. In this study, soils nearby a typical coking plant were sampled to assess the impact of coke production on the surrounding residential areas and human health. The mean concentration of PAHs and their derivatives in residential area soils nearby the coke plant was 4270 ng/g dw, which was 1 order of magnitude higher than that observed in areas far from the coke plant and approximately 4 times lower than that revealed the coke plant. In addition, the results showed that coking processing area was the most contaminant area of the coke plant (mean: 74.4 μg/g dw), where was also the main source of pollutants in residential areas. In terms of vertical soils in coking plant, the maximum levels of chemicals (mean: 205 μg/g dw) were presented at the leakage of underground pipelines, where were much higher than those in surface soils, and decreased with the increase of depth. The analysis of variance (ANOVA) results showed obvious differences in the concentrations of 6-nitrochrysene between the plant, residential areas and control areas. Meanwhile, 6-nitrochrysene had potential cancer risk (CR) for human in the coking site. Thus, 6-nitrochrysene was the most noteworthy PAH derivatives. Furthermore, the CR (mean: 5.94 × 10^-5) and toxic equivalent quantities (TEQs) (mean: 14.8 μg·TEQ/g) of PAHs and their derivatives was assessed in this study. This finding suggested that PAHs and their derivatives especially those extremely toxic chemicals (Nitro-PAHs (NPAHs) and Br/Cl-PAHs (XPAHs)) might pose a potential health risk to residents nearby the coke plant. The current study provides further insights into the pollution characteristics of PAHs and their derivatives in coke plants and potential risks to the workers and surrounding residents.

Determination of particulate polycyclic aromatic hydrocarbons in ambient air by gas chromatography-mass spectrometry after molecularly imprinted polymer extraction

A solid phase extraction procedure (SPE) is described for the quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter (PM), as ubiquitous environmental pollutants routinely measured in air quality monitoring. A SPE cartridge was used based on a molecular imprinted polymer (MIP-SPE) properly tailored for selective retention of PAHs with 4 and more benzene fused rings. The performance of the clean-up procedure was evaluated with the specific concern of selective purification towards saturated hydrocarbons, which are the PM components mostly interfering GC analysis of target PAHs. Under optimized operative conditions, the MIP-SPE provided analyte recovery close to 95% for heavier PAHs, from benzo(α)pyrene to benzo(ghi)perylene, and close to 90% for four benzene rings PAHs, with good reproducibility (RSDs: 2.5%-5.9%). Otherwise, C₁₇-C₃₂n-alkanes were nearly completely removed. The proposed method was critically compared with Solid Phase Micro Extraction (SPME) using a polyacrylate fiber. Both methods were successfully applied to the analysis of ambient PM_2.5 samples collected at an urban polluted site. Between the two procedures, the MIP-SPE provided the highest recovery (R% ≥ 93%) for PAHs with 5 and more benzene rings, but lower for lighter PAHs. In contrast, SPME showed a mean acceptable R% value (∼ 80%) for all the investigated PAHs, except for the heaviest PAHs in the most polluted samples (R%: 110%-138%), suggesting an incomplete purification from the interfering n-hydrocarbons.

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.

Optical properties, molecular characterizations, and oxidative potentials of different polarity levels of water-soluble organic matters in winter PM2.5 in six China's megacities

Humic-like substances (HULIS) accounted for a great fraction of water-soluble organic matter (WSOM) in PM_2.5, which efficiently absorb ultraviolet (UV) radiation and pose climate and health impacts. In this study, the molecular structure, optical properties, and oxidative potential (OP) of acid- and neutral-HULIS (denoted as HULIS-a, and HULIS-n, respectively), and high-polarity WSOM (HP-WSOM) were investigated in winter PM_2.5 collected at six China's megacities. For both carbon levels and optical absorption coefficients (b_{abs_365}), HULIS-a/HULIS-n/HP-WSOM showed significant spatial differences. For each city, the carbon levels and b_{abs_365} follow a similar order of HULIS-n > HULIS-a > HP-WSOM. Besides, the b_{abs_365} of HULIS-n and HULIS-a showed the same order of Harbin > Beijing ≈ Wuhan > Xi'an > Guangzhou > Chengdu, while HP-WSOM exhibited an order of Wuhan > Chengdu > Xi'an > Harbin > Beijing > Guangzhou. Both HULIS-a and HULIS-n were abundant in aromatic and aliphatic compounds, whereas HP-WSOM was dominated by a carboxylic acid group. The OP (in unit of nmol H₂O₂ μg^-1C) followed the order of HP-WSOM > HULIS-a > HULIS-n in all the cities. The OPs of HULIS-a, HULIS-n, and HP-WSOM in Harbin and Beijing were much higher than those of other cities, attributing to the high contribution from biomass burning. Highly positive correlations between reactive oxygen species (ROS) of HULIS-a and MAE₃₆₅ were obtained in Chengdu, Wuhan, and Harbin, but ROS of HULIS-n had stronger correlation with MAE₃₆₅ in Harbin, Chengdu, and Xi'an.

Nitrated and oxygenated polycyclic aromatic hydrocarbons emissions from solid fuel combustion in rural China: Database of 12 real-world scenarios for residential cooking and heating activities

Polycyclic aromatic hydrocarbons (PAHs) derivatives such as oxygenated PAHs (oPAHs) and nitrated PAHs (nPAHs), are receiving raising concerns due to their high toxic potential. Incomplete solid fuel combustion can release large quantities of PAHs derivatives, especially in low-efficiency domestic stoves. In this study, field measurements were conducted in rural Chinese homes to determine emissions of nPAHs and oPAHs from solid fuel combustion. A total of 12 fuel-stove combinations including cooking and space heating activities were investigated. Emission factors (EFs) of total nPAHs and oPAHs were in the range of 1.0-682.1 μg/kg and 0.01-131.7 mg/kg, respectively, with arithmetic means and stand deviations of 53.5 ± 72.5 μg/kg and 13.9 ± 24.4 mg/kg, respectively. The EFs of nPAHs and oPAHs for coal combustion (including honeycomb briquette, coal chunk, and peat tested in this study) were 30.2 ± 28.1 μg/kg and 1.5 ± 2.9 mg/kg, respectively, much lower than that for biomass burning (p < 0.05). The combustion phase could significantly affect the PAHs derivative emissions with higher emissions at initial phase than that at stable phase. Fuel type was found to affect the EFs, composition profiles, and ratios of PAHs derivatives to parent PAHs. This study tries to have an insight of PAHs derivative emissions from various solid fuel combustion, which would be useful in understanding the atmospheric PAHs derivative pollutions in China.

Chemical signatures of polycyclic aromatic hydrocarbons in the emissions from in situ oil burns

This study characterized the parent and alkylated polycyclic aromatic hydrocarbons (PAHs) in gaseous and particulate emissions from the in situ burning (ISB) of oils. The experimental results indicate that the burning of the heavy oil produced the most PAH emissions because of its longest burning time. In addition, the parent PAHs mainly exist in the particulate phase, while alkylated PAHs mostly accumulate in the gaseous phase. In particular, the diagnostic-ratios of PAHs with great stability in both gaseous and particulate emissions from ISB are identified by comparing the laboratory and field data. The presences of bell-, slope- and V-shaped distribution patterns of alkylated PAHs in the emissions precisely indicate their sources to be petrogenic and pyrogenic processes occurring during ISB. The formation of 2-methylanthracene during ISB is confirmed. The overall findings are expected to provide a prospective protocol to characterize PAH pollution from ISB emissions in case of oil spills.

Particle size-resolved emission characteristics of complex polycyclic aromatic hydrocarbon (PAH) mixtures from various combustion sources

Combustion of domestic solid fuels is a significant source of polycyclic aromatic hydrocarbons (PAHs). Some oxygenated PAHs (o-PAHs) and PAHs with molecular weight of 302 (MW302 PAHs) are more toxic than the traditional 16 priority PAHs, whereas their emissions were much less elucidated. This study characterized the size-dependent emissions of parent PAHs (p-PAHs), o-PAHs, and MW302 PAHs from various combustion sources. The estimated emission factors (eEFs) from biomass burning sources were highest for most of the PAHs (391-8928 μg/kg), much higher than that of anthracite coal combustion (43.0-145 μg/kg), both which were operated in an indoor stove. Cigarette smoking had a high eEF of o-PAHs (240 ng/g). MW302 PAHs were not found in the emissions of smoking, cooking, and vehicular exhausts. Particle-size distributions of PAHs were compound- and source-dependent, and the tendency to associate with smaller particles was observed especially in biomass burning and cigarette smoking sources. Furthermore, the inter-source differences in PAH eEFs were associated with their dominance in fine particles. PAH composition profiles also varied with the particle size, showing increasing contributions of large-molecule PAHs with decreasing sizes in most cases. The size distributions of p-PAHs are much more significantly dependent on their n-octanol/air partition coefficients and vapor pressures than those of o-PAHs, suggesting differences in mechanisms governing their distributions. Several molecular diagnostic ratios (MDRs), including two based on MW302 PAHs, specific to these combustion scenarios were identified. However, the MDRs within some sources are also strongly size-dependent, providing a new explanation for the uncertainty in their application for source identification of PAHs. This work also highlights the necessity for understanding the size-resolved atmospheric behaviors and fate of PAHs after their emission.

Field measurements of PM2.5 emissions from typical solid fuel combustion in rural households in Fenhe Basin, China

Solid fuel is the most widely used energy source for cooking and heating in the rural households in developing countries. In this study, emissions from 13 fuel-stove combinations were studied in two typical rural villages in the Fenhe Basin, Shanxi Province, China. This study gathered data on the emission characteristics of particles with an aerodynamic diameter of ≤2.5 μm (PM_2.5), organic carbon (OC), elemental carbon (EC), and 21 parent and oxygenated polycyclic aromatic hydrocarbons (pPAHs and oPAHs, respectively); the mechanism of gas formation was also determined. The PM_2.5 EFs of biomass burning ranged from 4.11 ± 2.12 to 138 ± 47.2 g/kg, which was higher than that of coal combustion (1.57 ± 0.89 to 4.11 ± 0.63 g/kg). Notably, the average PM_2.5 EFs of biomass burning in a traditional stove and elevated kang were 50.9 ± 13.8 and 23.0 ± 3.99 g/kg, respectively, suggesting that the elevated kang had superior emission mitigation. Wood pellet burning in a biomass furnace yielded lower PM_2.5 EFs than firewood burning in the biomass furnace, which demonstrated wood pellet combustion's superior emission reduction effect. The relative contribution of OC4 to OC subfractions may be useable as tools for identifying the sources of coal and biomass burning. Regarding PAHs, biomass with abundant lignin pyrolysis produced numerous hydroxyl radicals that were conducive to the release of greater proportions of oPAHs. By contrast, pPAHs had greater relative contributions in coal combustion. Regarding gaseous pollutants, its formation mechanism varied with combustion phase. Emission differences between the two phases were mainly determined by the relative contributions of volatile C/N and char. Clarifying the pollutant formation mechanism can better guide the implementation of emission control from household solid fuel combustion.

A comprehensive evaluation of PM2.5-bound PAHs and their derivative in winter from six megacities in China: Insight the source-dependent health risk and secondary reactions

Atmospheric PAHs (polycyclic aromatic hydrocarbons) and their derivatives are a global concern that influences environments and threatens human health. Concentrations of 52 PAHs and the main derivatives in six Chinese megacities were measured in the winter of 2019. The concentrations of ∑PAHs (sum of 52 PAHs) ranged from 19.42 ± 7.68 to 65.40 ± 29.84 ng m^-3, with significantly higher levels in northern cities (Harbin [HB], Beijing [BJ], and Xi'an [XA]) than southern ones (Wuhan [WH], Chengdu [CD] and Guangzhou [GZ]). Source apportionment of ∑PAHs was conducted by the PMF model and results showed coal combustion and traffic emissions were the two dominant sources, which dominated ∑PAHs in northern and southern cities, respectively. Biomass burning was also characterized as a crucial source of ∑PAHs and showed extremely high contributions in XA (42.5%). Assisted by the individual PAH source apportionment results, the source-depend TEQ (total BaP equivalent) and incremental lifetime cancer risk (ILCR) were firstly reported in these cities. The results highlighted the contributions of coal combustion and biomass burning to both TEQ and ILCR, which were underestimated by ∑PAHs source apportionment. Secondary organic aerosol-derived PAHs were demonstrated to increase the TEQ compared with the fresh PAHs and three parameters, namely temperature, relative humidity, and O₃ concentrations were characterized by multiple linear regression as the principal factors influencing secondary reactions of PAHs in winter. This study provides accurate human health-orientated results and potential control measures to mitigate the toxicity of secondary formed PAHs, and significantly decrease the uncertainty level of traditional methods. The results also revealed great progress in air pollution control by the Chinese government in the past 20 years, but still a long way to go to formulate strict emission control strategies from both environmental and human health-protective perspectives.

Seasonal distribution of PM2.5-bound polycyclic aromatic hydrocarbons as a critical indicator of air quality and health impact in a coastal-urban region of Poland

This study focuses on the inter-seasonal distribution and variability of thirteen native PAHs adsorbed onto respirable PM_2.5 fraction collected in a coastal-urban region of northern Poland, in 2019. The backward trajectory analysis and several diagnostic ratios were applied to determine seasonal profiles of PAH congeners and their major sources in airborne samples. The annual cumulative mean value of total PAHs in PM_2.5 was 6.92 ± 10.1 ng m^-3, varying in the following range: 0.32 ng m^-3 (May) - 68.57 ng m^-3 (January). Seasonal mass concentrations of total particulate PAHs were ranked as follows: summer (1.27 ng m^-3) < spring (4.83 ng m^-3) < autumn (6.16 ng m^-3) < winter (18.5 ng m^-3). Clear seasonal differences in PAH concentrations can be explained by direct impact of local and regional urban/industrial activities, with priority winter contribution of coal combustion in residential and commercial sectors. In addition, for summer measurements the diagnostic ratios indicated that high molecular weight PAHs were mainly derived from vehicle emission and petrochemical industry, while relatively low mass contribution of 4-ring congeners to the total sum of PAHs was attributed to photochemical processing. The analysis of meteorological parameters (temperature, relative humidity) and gaseous precursors (SO₂, NO₂, NO_x, O₃ and CO) exhibits their statistically significant correlations with PAHs, indicating local/regional primary emission. The incremental lifetime cancer risk was 1.23 × 10^-5, suggesting potential toxicity and carcinogenicity for adult females and males. This study highlights the importance of the implementation of health risk assessment model in urbanized coastal zones.

Emission factors, characteristics, and gas-particle partitioning of polycyclic aromatic hydrocarbons in PM2.5 emitted for the typical solid fuel combustions in rural Guanzhong Plain, China

Solid fuel is a the most dominant energy source for household usages in developing countries. In this study, emission characteristics on organic carbon (OC), elemental carbon (EC) and fifty-two polycyclic aromatic hydrocarbons (PAHs) in gaseous and particulate phases from seven fuel-stove combinations were studied in a typical rural village in northwest China. For the PAHs, the highest gaseous and particulate phase emission factors (EFs) were both observed for bituminous coal with one-stage stoves, ranging from 459 ± 154 to 1.09 ± 0.36 × 10³ mg kg^-1. In contrast, the PAHs EFs for the clean briquette coal with two-stage stoves were two orders of magnitude lower than those of the bituminous coals. For parent PAHs (pPAHs) and total quantified PAHs (∑PAHs), they mainly contributed in gaseous phases with compositions of 69-79% and 64-70%, respectively. The gas-to-particle partitioning was mostly governed by the absorption. Moreover, the correlation coefficient (r) between EC and ∑PAHs, OC and parent PAHs (pPAHs), OC and nitro PAHs (nPAHs) were 0.81, 0.67 and 0.85, respectively, supporting that the PAHs species were potential precursors to the EC formation during the solid fuel combustion. The correlation analyses in this study further deduced that the formations of pPAHs and nPAHs were more closely related to that of OC than alkylated PAHs (aPAHs) and oxygenated PAHs (oPAHs). Diagnostic ratios of selective PAHs were calculated and evaluated as well. Among those, the ratio of retene (RET)/[RET + chyrene (CHR)] was found to be an efficient tool to distinguish coal combustion and biomass burning. In general, it was found that the amounts of pollutant emissions from clean briquette coal combustion were definitely lower than those from bituminous coal and biomass combustions. It is thus necessary to introduce and recommend the use of cleaner briquette coal as energy source.

Polycyclic Aromatic Hydrocarbon Sorption by Functionalized Humic Acids Immobilized in Micro- and Nano-Zeolites

Polycyclic aromatic hydrocarbons (PAHs) are hazardous compounds originating from anthropogenic activity. Due to their carcinogenic properties for humans, several technologies have been developed for PAH removal. Sorption with natural and organic materials is currently one of the most studied due to its low cost and its environmentally friendly nature. In this work, a hybrid sorbent involving functionalized humic acids (HAs) and nano-zeolite is proposed to entrap PAHs. The use of functionalized HAs immobilized in a porous support is designed to address the instability of HAs in solution, which has been already reported. HA functionalization was carried out to increase the non-polarity of HAs and aliphatic group formation. The HAs were functionalized by esterification/etherification with alkyl halides, and their chemical changes were verified by FTIR and NMR. The sorption isotherms of the functionalized HAs in micro- and nano-zeolites were used to assess the performance of the nano-zeolites in adsorbing these HAs. The hybrid support allowed the removal of anthracene and pyrene at percentages higher than 90%; fluoranthene, of angular molecular structure, was adsorbed at 85%. PAHs are ubiquitous in the environment, and a stable sorption of them in solid matrices will allow their removal from the environment through effective and environmentally friendly methods.

Chemical source profiles of particulate matter and gases emitted from solid fuels for residential cooking and heating scenarios in Qinghai-Tibetan Plateau

Incomplete combustion of solid fuels (animal dung and bituminous coal) is a common phenomenon during residential cooking and heating in the Qinghai-Tibetan Plateau (QTP), resulting in large amounts of pollutants emitted into the atmosphere. This study investigated the pollutant emissions from six burning scenarios (heating and cooking with each of the three different fuels: yak dung, sheep dung, and bitumite) in the QTP's pastoral dwellings. Target pollutants such as carbon monoxide (CO), gas-phase polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), fine particles (PM_2.5, particulate matter with an aerodynamic diameter < 2.5 μm), carbonaceous aerosols, water-soluble ions, and particle-phase PAHs were investigated. Emission factors (EFs) (mean ± standard deviation) of PM_2.5 from the six scenarios were in the range of 1.21 ± 0.47-7.03 ± 1.95 g kg^-1, of which over 60% mass fractions were carbonaceous aerosols. The ratio of organic carbon to elemental carbon ranged from 9.6 ± 2.7-33.4 ± 11.5 and 81.7 ± 30.4-91.9 ± 29.0 for dung and bitumite burning, respectively. These values were much larger than those reported in the literature, likely because of the region's high altitudes-where the oxygen level is approximately 65% of that at the sea level-thus providing a deficient air supply to stoves. However, the toxicity and carcinogenicity of PAHs emitted from solid fuel combustion in the QTP are significant, despite a slightly lower benzo(a)pyrene-equivalent carcinogenic potency (Bap_eq) in this study than in the literature. The gas-to-particle partitioning coefficient of PAHs and VOC emission profiles in the QTP differed significantly from those reported for other regions in the literature. More attention should be paid to the emissions of PAH derivatives (oxygenated PAHs and nitro-PAHs), considering their enhanced light-absorbing ability and high BaP_eq from solid fuel combustion in the QTP.

Mutagenicity risk prediction of PAH and derivative mixtures by in silico simulations oriented from CYP compound I-mediated metabolic activation

PAHs and their derivatives are the main sources of mutagenicity and carcinogenicity in airborne particular matter and cause serious public health and environmental problems. Risk assessment is challenging due to the mixed nature and deficiency of toxicity data of most PAHs and their derivatives. Cytochrome P450 enzymes (CYPs) play important roles in PAH-induced carcinogenicity via metabolic activation, and CYP conformations with compound I structures strongly influence metabolic sites and metabolite species. In this study, complexes of BaP with CYP1A1, CYP1B1 or CYP2C19 compound I were successfully simulated by QM/MM methods and verified by metabolic clearance, and the mutagenicity of chemicals was then predicted by the BaP-7,8-epoxide-related metabolic conformation fitness (MCF) approach, which was validated by Ames tests, showing satisfying accuracy (R² = 0.46-0.66). Furthermore, a prediction model of the mutagenicity risk of PAH and derivative mixtures was established based on the relative potential factor (RPF) approach and the RPF calculated from the mathematical relationship between the minimum MCF (MCF_min) and RPF, which was successfully validated by the mutagenesis of PAH and derivative mixture mimic-simulating PM2.5 samples collected in eastern China. This study provides fast reliable tools for assessing risk of the complex components of environmental PAHs and their derivatives.

Emissions of particulate PAHs from solid fuel combustion in indoor cookstoves

Residential solid fuel combustion is a major emission source of PAHs (polycyclic aromatic hydrocarbons) in most developing countries, including China; however, accurate estimates of PAH emissions are often challenged by limited real-world emission factors (EFs) under field conditions, which can hardly be repeated in laboratory-controlled tests. In this study, a series of field measurements was conducted to determine the emissions of 28 PAHs from different fuel-stove combinations. A total of 14 fuel-stove combinations were studied. The total EFs of 28 PAHs (EF_PAH28), on the basis of fuel mass, ranged from 20.7 to 535 mg/kg, with relatively lower EFs for coal than for biomass. Biomass burning in gasifier stoves had lower PAH EFs and fewer toxic PAH species than biomass burning in traditional brick stoves. Fuel type was a significant factor affecting PAH emissions, while stove difference had a relatively smaller influence. Much higher EFs were found from these field tests than from the idealized laboratory tests, which indicated significant underestimation in inventories based on the laboratory-based EFs. Biomass and coal had different profiles, with larger intra-fuel variations in coal than those in biomass. Highly variable values of some, though not all, commonly used isomer ratios indicated substantial biases in source apportionment relying on single or simple ratios without correction, and the MCE was found to be significantly corrected with some ratios.

Parent, alkylated, oxygenated and nitrated polycyclic aromatic hydrocarbons in PM2.5 emitted from residential biomass burning and coal combustion: A novel database of 14 heating scenarios

To characterize the emissions of polycyclic aromatic hydrocarbons (PAHs) from residential biomass burning and coal combustion in field environments, smoke samples were collected from the combustion of six types of biomass in heated kangs and four types of coal in traditional stoves and semi-gasifier stoves. The emission factors (EFs) of the total PAH were in the range of 84.5-344 mg/kg for biomass burning, with lower EFs for biomass with higher densities, and in the range of 38.0-206 mg/kg for coal combustion, with lower EFs for coals with higher maturity. Moreover, EFs were lower from high-density biomass fuels (wood trunk, 84.5 ± 11.3 mg/kg) than low-maturity coals (bituminous coal, 206 ± 16.5 mg/kg). Parent, oxygenated, alkylated, and nitrated PAHs accounted for 81.1%, 12.6%, 6.2%, and 0.1%, respectively, of the total-PAH EFs from biomass burning, and 84.7%, 13.8%, 1.4%, and 0.1%, respectively, of the total-PAH EFs from coal combustion. PAH source profiles differed negligibly between biomass fuels but differed significantly between bituminous coal and anthracite coal fuels. The characteristic species of sources were phenanthrene, 9-fluorenone, and 2-nitrobiphenyl for biomass burning, and were phenanthrene, benzo[ghi]perylene, 1,4-naphthoquinone, and 2-nitrobiphenyl for coal combustion. The ratios of benzo[b]fluoranthene/(benzo[b]fluoranthene + benzo[k]fluoranthene) were 0.40-0.45 for biomass burning and 0.89-0.91 for coal combustion, and these significantly different values constitute unique markers for distinguishing these fuels in source apportionment. Benzo[a]pyrene-equivalent factor emissions were 2.79-11.3 mg/kg for biomass and 7.49-41.9 mg/kg for coal, where parent PAHs contributed 92.0%-95.1% from biomass burning and 98.6%-98.8% from coal combustion. Total-PAH emissions from residential heating were 1552 t across Shaanxi province, to which wheat straw (445 t) in biomass burning and bituminous coal (438 t) in coal combustion were the highest contributors. Results from this study provide crucial knowledge for the source identification of PAHs as well as for the design of abatement strategies against pollutant emissions.

Analysis and Risk Assessment of Organic Pollutants in Surface Water from Xujiahe Basin, China

In this study, organic compounds were screened in surface water collected from Xujiahe basin, China by gas chromatography-mass spectrometry (GC-MS). A total of 51 compounds were identified including 14 organochlorine pesticides (OCPs), 9 organophosphorus pesticides (OPs), 16 polycyclic aromatic hydrocarbons (PAHs) and 12 chlorobenzene (CBs). The concentrations of OCPs, PAHs and CBs were generally low. The concentrations of OCPs in Xujiahe reservoir ranged from N.D. to 35.6 ng/L, the concentrations of PAHs ranged from N.D. to 19.8 ng/L and the concentrations of CBs ranged from 10.3 to 124.6 ng/L. The Ecological Structure Activity Relationships (ECOSAR) model was employed to directly predict the integrated toxicity indexes of 51 organic pollutants. The risk quotient (RQ) values of most of the organic compounds in the water samples were acceptable for their ecological risk.