Occurrence, gas/particle partitioning and carcinogenic risk of polycyclic aromatic hydrocarbons and their oxygen and nitrogen containing derivatives in Xi'an, central China

The occurrence, sources, and health risks of substituted polycyclic aromatic hydrocarbons (SPAHs) cannot be ignored

Similar to parent polycyclic aromatic hydrocarbons (PPAHs), substituted PAHs (SPAHs) are prevalent in the environment and harmful to humans. However, they have not received much attention. This study investigated the occurrence, distribution, and sources of 10 PPAHs and 15 SPAHs in soil, water, and indoor and outdoor PM2.5 and dust in high-exposure areas (EAH) near industrial parks and low-exposure areas (EAL) far from industrial parks. PAH pollution in all media was more severe in the EAH than in the EAL. All SPAHs were detected in this study, with alkylated and oxygenated PAHs being predominant. Additionally, 3-OH-BaP and 1-OH-Pyr were detected in all dust samples in this study, and 6-N-Chr, a compound with carcinogenicity 10 times higher than that of BaP, was detected at high levels in all tap water samples. According to the indoor-outdoor ratio, PAHs in indoor PM2.5 in the EAH mainly originated from indoor pollution sources; however, those in the EAL were simultaneously affected by indoor-outdoor air exchange and indoor sources. Most target PAHs tended to deposit from air to dust, and this tendency was significantly negatively associated with the octanol-air partitioning coefficient of PAHs. SPAHs in the environment are primarily derived from the petroleum industry and the mixed combustion of gasoline, biomass, and coal. The toxicity equivalence factors of SPAHs were predicted using QSAR models to assess their lifetime carcinogenic risk (ILCR). The ILCRtotal from PAHs for adults in the EAH was >10-4. Though the levels of 6-N-Chr and 1-Me-Pyr in the environment were markedly lower than those of PPAHs, their ILCRs from PM2.5 inhalation and dermal contact with water exceeded 10-6. This study is significant for recognizing and controlling the health risks associated with SPAHs in humans.

Sediment record of polycyclic aromatic compounds and black carbon over the last ~400 years in Sanjiaolongwan Maar Lake, northeast China

Fuel usage is an important catalyst for socio-economic development and human well-being. Human activities have resulted in significant increases in emissions from biomass burning (BB) and fossil fuel (FF) combustion which have significantly adversely affected human, ecosystem, and planetary health in this era of the Anthropocene. Sanjiaolongwan Maar Lake (SJLW), as a typical crater lake, uniquely receives atmospheric deposition from long-distance transport, and thus, its sediments reflect environmental change and human impacts on a broad scale. In this study, the concentrations and compositions of combustion products, including polycyclic aromatic compounds (PACs, i.e., polycyclic aromatic hydrocarbons (PAHs) and their oxygenated (OPAHs) and nitrogen heterocyclic derivatives (AZAs)) and black carbon (BC and its constituents char and soot), in SJLW over the past 400 years were investigated. The results showed that the PACs and soot concentrations and fluxes in SJLW have rapidly increased since 1950. The concentrations of the total PACs increased ~4 times after the 1950s. Such a fast increase is consistent with the rapid industrialization after the establishment of the People's Republic of China (PRC), which has further accelerated beginning with the implementation of the reform and opening up policy of the PRC in 1978. Moreover, the variations in the compositions of PACs, as well as the decrease in the char/soot ratio, demonstrate a transition in energy usage from BB to FF combustion. The decrease in the benzo[e]pyrene/benzo[a]pyrene ratio indicated an increase in local emissions (because of increasing industrialization in northeast China). The temporal profile of perylene concentrations, fluxes, and perylene/5-ring PAHs ratios strongly suggest that perylene mainly originated from non-pyrogenic sources. The records of PACs and BC in SJLW offer valuable perspectives on human impacts and provide important references for the start of the Anthropocene.

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.

Multivariate optimization of a green procedure for determination of emerging polycyclic aromatic nitrogen heterocycles in PM2.5 from sites with different characteristics

Emerging polycyclic aromatic nitrogen heterocycles (PANHs) contributes significantly to the health risk associated with inhaling polluted air. However, there is a lack of analytical methods with the needed performance to their determination. This study presents the optimization and validation for the first time of a green microscale extraction procedure for the determination of twenty-one PANHs, including carbazole, indole, and quinolone classes, in particulate matter (PM2.5) samples by gas chromatography-mass spectrometry. A simplex-centroid mixture design and full factorial design (23) were employed to optimize the following extraction parameters: type and volume of solvent, sample size, extraction time, and necessity of a cleanup step. Low limits of detection and quantification (LOD < 0.97 pg m-3 and LOQ < 3.24 pg m-3, respectively) were obtained in terms of matrix-matched calibration. The accuracy and precision of the method were adequate, with recoveries in three levels between 73 to 120% and intraday and interday relative standard deviations from 2.0 to 12.9% and 7.3 to 18.9%, respectively. The green character of the method was evaluated using the Analytical Greenness (AGREE) tool, where a score of 0.69 was obtained, indicating a great green procedure. The method was applied to PM2.5 samples collected from sites with different characteristics; the concentrations ranged from 69.3 pg m-3 (2-methylcarbazole) to 11,874 pg m-3 (carbazole) for individual PANHs and from 2306 to 24,530 pg m-3 for ∑21PANHs. Principal component analysis (PCA) and hierarchical clustering enabled discrimination of the sampling sites according to the PANHs concentrations. The score plots formed two distinct groups, one with samples containing higher concentrations of PANHs, corresponding to sites with a major influence from diesel emissions, and another group with minor PANH contents, corresponding to sites impacted by emissions from urban traffic and industrial activities.

Characterization and Risk Assessment of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and their Derivatives Emitted from a Typical Pesticide Factory in China

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives have received extensive attention due to their negative effects on the environment and on human health. However, few studies have performed comprehensive assessments of PAHs emitted from pesticide factories. This study assessed the concentration, composition, and health risk of 52 PM_2.5-bound PAHs during the daytime and nighttime in the vicinity of a typical pesticide factory. The total concentration of 52 PAHs (Σ52PAHs) ranged from 53.04 to 663.55 ng/m³. No significant differences were observed between daytime and nighttime PAH concentrations. The average concentrations of twenty-two parent PAHs, seven alkylated PAHs, ten oxygenated PAHs, and twelve nitrated PAHs were 112.55 ± 89.69, 18.05 ± 13.76, 66.13 ± 54.79, and 3.90 ± 2.24 ng/m³, respectively. A higher proportion of high-molecular-weight (4-5 rings) PAHs than low-molecular-weight (2-3 rings) PAHs was observed. This was likely due to the high-temperature combustion of fuels. Analysis of diagnostic ratios indicated that the PAHs were likely derived from coal combustion and mixed sources. The total carcinogenic equivalent toxicity ranged from 15.93 to 181.27 ng/m³. The incremental lifetime cancer risk from inhalation, ingestion, and dermal contact with the PAHs was 2.33 × 10^-3 for men and 2.53 × 10^-3 for women, and the loss of life expectancy due to the PAHs was 11,915 min (about 0.023 year) for men and 12,952 min (about 0.025 year) for women. These results suggest that long-term exposure to PM_2.5 emissions from a pesticide factory has significant adverse effects on health. The study results support implementing the characterization of PAH emissions from pesticide factories and provides a scientific basis for optimizing the living environment around pesticide factories.

Investigating industrial PAH air pollution in relation to population exposure in major countries: A scoring approach

Polycyclic aromatic hydrocarbons (PAHs) are common air pollutants worldwide, associated with industrial processes. In the general population, both modeling and field studies revealed a positive correlation between air PAH concentrations and urinary PAH metabolite levels. Many countries lack population urinary data that correspond to local PAH air concentrations. Thus, we proposed a scoring-based approximate approach to investigating that correlation in selected countries, hypothesizing that PAH air concentrations in selected regions could represent the national air quality influenced by industrial emission and further correlate to PAH internal exposure in the general population. This research compiled 85 peer-reviewed journal articles and 9 official monitoring datasets/reports covering 34 countries, 16 of which with both atmospheric PAH data and human biomonitoring data. For the air pollution score (AirS), Egypt had the highest AirS at 0.94 and Pakistan was at the bottom of the score ranking at -1.95, as well as the median in the UK (AirS: 0.50). For the population exposure score (ExpS), China gained the top ExpS at 0.44 and Spain was with the lowest ExpS of -1.52, with the median value in Italy (ExpS: 0.43). Through the correlation analysis, atmospheric PAHs and their corresponding urinary metabolites provided a positive relationship to a diverse extent, indicating that the related urinary metabolites could reflect the population's exposure to specific atmospheric PAHs. The findings also revealed that in the 16 selected countries, AirS indexes were positively correlated with ExpS indexes, implying that higher PAH levels in the air may lead to elevated metabolite urinary levels in general populations. Furthermore, lowering PAH air concentrations could reduce population internal PAH exposure, implying that strict PAH air regulation or emission would reduce health risks for general populations. Notably, this study was an ideal theoretical research based on proposed assumptions to some extent. Further research should focus on understanding exposure pathways, protecting vulnerable populations, and improving the PAH database to optimize PAH pollution control.

Overhead AC powerlines and rain can alter the electric charge distribution on airborne particles - Implications for aerosol dispersion and lung deposition

Corona ions from high voltage power lines (HVPL) can increase electrostatic charge on airborne pollutant particulates, possibly increasing received dose upon inhalation. To investigate the potential increased risk of childhood leukemia associated with residence near alternating current (AC) HVPL, we measured the particle charge state and atmospheric electricity parameters upwind, downwind and away from HVPL. Although we observed noticeable charge state alteration from background levels, most HVPL do not significantly increase charge magnitude. Particular HVPL types are shown to have most effect, increasing net charge to 15 times that at background. However, the magnitude of charge alteration during rainfall is comparable with the most extreme HVPL measurement. On current evidence, based on the current adult lung model, we suggest that although charge is sometimes enhanced to levels which may alter atmospheric particle dynamics, increased lung deposition is unlikely.

Atmospheric benzo[a]pyrene in the Yangtze River Delta, China: pollution level and lung cancer risk in 2016 and future predictions

The Yangtze River Delta (YRD) has undergone widespread polycyclic aromatic hydrocarbon (PAH) pollution. In this study, we simulated the spatial distribution of atmospheric benzo[a]pyrene (BaP, the most carcinogenic PAH) in the YRD in 2016 and 2030 under different emission scenarios using a 3-D atmospheric transport model and evaluated the lung cancer risks posed by BaP during the study years. The purpose of this study is to suggest targeted policy recommendations for policy-makers to mitigate BaP pollution through numerical simulation. Our results showed that the average BaP concentration in the YRD was 0.30 ng/m3 in 2016; however, a significant spatial variation was observed, with the highest BaP concentration in Shanghai (0.59 ng/m3). The population-weighted incremental lifetime lung cancer risk (PILCR) was 6.67 × 10-6 in 2016, whereas it ranged from 2.70 × 10-6 to 1.05 × 10-5 in 2030 under the five emission scenarios. A higher future population density in the YRD region could increase lung cancer risk. In all scenarios, Shanghai had the highest number of lung cancer cases (range: 208-476). The results suggest that BaP pollution could be effectively improved through the synergistic effect of reducing activity levels and improving technology. Finally, we provide specific suggested pollution control strategies (e.g., accelerating the use of clean energy in rural areas) for atmospheric BaP in the YRD.

Distinct seasonal variability of source-dependent health risks from PM2.5-bound PAHs and related derivatives in a megacity, southwest China: Implications for the significance of secondary formation

In contrast to polycyclic aromatic hydrocarbons (PAHs) which have been regularly monitored, the source-dependent health risk of their derivatives in ambient environment has not been well understood, especially regarding seasonal variability. In this study, oxygenated and nitrated PAHs (OPAHs and NPAHs) in PM_2.5 samples from different seasons in urban Chongqing were analyzed and compared with PAHs from a human health perspective. Benzo[a]pyrene equivalent concentrations (BaP_eq) were annually averaged at 6.13 ± 8.97 ng/m³ (n = 118) in the present study, with highest levels in winter followed by spring, autumn, and summer. The BaP_eq values of OPAHs were higher than PAHs in spring and summer with seasonal averaged value up to 3.7 times of that for PAHs, manifesting significant underestimation of the health impact if only PAHs were considered. Incremental lifetime cancer risk (ILCR) model results suggested that the potential cancer risks were accumulated mostly from inhalation exposure during infancy and adulthood. Furthermore, in comparison with PAHs, OPAHs, mainly 6H-Benzo[c,d]pyren-6-one, had significant contribution to cancer risks (annually averaged at 58.3 %). Source-dependent cancer risks based on positive matrix factorization model denoted secondary formed PAH derivatives as a critical contributor to cancer risk, particularly in spring and summer (attributed to about 61 % of ILCR). The enhanced secondary formation of PAH derivatives during spring and summer was partially justified by diagnostic ratios and further analysis revealed that higher temperature, higher O₃ level, and lower relative humidity besides stronger solar intensity during these two seasons as the most likely causes of this seasonal variation. Results in this study emphasizes that more knowledge on the formation and toxicity of OPAHs is imperative, especially in the context of complex PM_2.5-ozone pollution in China.

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.

Bioaccessibility and bioavailability of NPAHs in soils using in vitro-in vivo assays: Comparison of laboratory and outdoor environmental aging effect

Aging process is one of the most important factors that markedly reduces bioaccessibility and bioavailability (bioac-bioav) of organic contaminants. However, only few data on comparison of the effects of laboratory artificial aging (LAA) and outdoor environmental aging (OEA) processes on nitrated polycyclic aromatic hydrocarbons (NPAHs) bioac-bioav are available. In the current study, oral bioac-bioav of NPAHs in LAA and OEA soils (aging time intervals: 0, 45, 90, 120 and 150 d) were measured by in vitro traditional Fed ORganic Estimation human Simulation Test (FOREhST) and Tenax improved FOREhST (TI-FOREhST) methods, and in vivo mouse model. Tenax significantly increased the bioaccessibility of NPAHs in freshly spiked and aging soils from 0.3-40.9 % to 15.6-95.3 %, and 0.3-40.9 % to 1.0-84.5 %, respectively. Aging significantly reduced the NPAHs bioaccessibility (from 36.5 % to 10.7 %, and 12.1 % to 5.1 % as measured by FOREhST and TI-FOREhST, respectively) and bioavailability (from 27.7 % to 9.9 %, as measured by mouse model). The changes in bioac-bioav were mainly observed within the first 120 d of aging. The statistical analyses of NPAHs bioac-bioav showed no significant difference (p > 0.05) among the aging time intervals in LAA and OEA soils, which demonstrated that the LAA can relatively represent the OEA. Determination of TOC content in LAA and OEA soil can intuitively reflect whether the difference of NPAHs bioac-bioav between two aging treatment groups is significant. The mean bioaccessibility of NPAHs in soil measured by TI-FOREhST (mean 20.6 %) is closer to the bioavailability measured by mouse model (mean 19.4 %), indicating that Tenax improved in vitro method is more reliable than traditional methods, to predict the bioavailability of NPAHs.

Size-resolved gas-particle partitioning characteristics of typical semi-volatile organic compounds in urban atmosphere

Understanding particle size distribution and size-resolved gas-particle partitioning of semi-volatile organic compounds (SVOCs) is important for characterizing their fate in atmosphere. However, the size-resolved gas-particle partitioning characteristics of SVOCs has not been adequately considered. To address this issue, the present study collected gaseous and size-fractioned particulate samples both in and outside of schools, offices, and residences in three districts of different urbanization levels in a megacity, Guangzhou, South China during two seasons. Typical SVOCs, including 15 polycyclic aromatic hydrocarbons (PAHs), six organophosphate esters and seven phthalic acid esters were measured. Emission sources, physicochemical properties, and environmental conditions at the sampling sites considerably impacted the spatiotemporal distribution patterns and particle size distribution of target SVOCs. Not all observed gas-particle partition coefficients (K_p) of target SVOCs were negatively correlated with subcooled liquid-vapor pressures (P_L⁰), probably because certain factors, such as the non-exchangeable part of the particle-bound SVOCs, were not considered in traditional gas-particle partition theories. Particle size was an important factor affecting gas-particle partitioning. Adsorption was the dominant mechanism for PAHs with high molecular weight in different particle modes. A new model was established to predict size-resolved K_p of PAHs with high molecular weight based on P_L⁰ and particle size.

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.

Extractable denuders for selective sampling of vapour phase organics in the atmosphere

Extractable denuders were designed to collect trace atmospheric semivolatile organic compounds with high volume (38.30 and 200 L/ min) samplers. Denuders were made of multichannel ceramic support coated with sodium silicate and functionalised with phenyl moieties. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzodioxins and polychlorinated dibenzofurans and chlorobenzenes in ambient air of a sub-urban area of Monterotondo, Italy, were sampled. Samplings were of 24 h, 48 h and 1 week period. Precision was determined using field triplicates and compared to the conventional high volume sampler methods. The fraction of analytes in the particle phase measured with the filter/ PUF system ranged from 0.2 % for naphthalene to 98.5 % for benzo(ghi)perylene; this fraction measured with the denuder ranged from 0.5 % for naphthalene to 99.0 % for benzo(ghi)perylene. A paired t-test indicated that these values were significantly (t = 3.58, P < 0.01) higher for the denuder. Results showed good repeatability (0.4-4.6 %), sampling efficiency (>99 %) and good capacity as variations in experimental efficiency were not observed also for longer (1 week) period sampling. As significant changes in efficiency were observed (0.7-5.6 %), the developed denuder cannot be reused more than once. However, it is possible to regenerate the denuder with a new silanization step. A good linear correlation was found plotting the vapour/particle distribution ratio versus the vapour pressure (R2 ranged between 0.59 and 0.84) and versus the octanol/air partition coefficient (R2 ranged between 0.85 and 0.88) of each selected SVOCs, in good agreement with the theoretical models for partitioning of SVOCs.

Occurrence, spatial patterns, air-seawater exchange, and atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) from the Northwest Pacific to Arctic Ocean

Numerous studies have elucidated the characteristics of polycyclic aromatic hydrocarbons (PAHs) in the Arctic; however, their behavior in different environments has not been studied at a large scale. To investigate the occurrence, spatial trends, air-seawater exchange and atmospheric deposition of 16 polycyclic aromatic hydrocarbons (PAHs), this study takes sample from the Northwest Pacific Ocean. to the Arctic Ocean.The concentrations of 16 PAHs in air and seawater ranged from 27 to 5658 pg/m³ and 34-338 ng/L, respectively. The air-seawater exchange flux of the region was calculated with a Whitman two-film model to be -82681-24613 ng/m²/day. Meanwhile, low-ring PAHs were transported from seawater to the air, while high-ring PAHs were transported from air to seawater. A correlation analysis between multiple environmental factors and particle phase ratio suggested that temperature might be the major driving factor for PAHs in the long-range atmospheric transport (LRAT) process. Moreover, the dry atmospheric deposition fluxes in the region were analyzed by considering environmental factors and the physicochemical properties of each PAHs monomer, these fluxes ranged from 0.001 to 696 ng/m²/day and were greater inshore than offshore and at higher latitudes. This study highlights that PAHs are affected by LRAT during their transport from Asia to Northwest Pacific and further to the Arctic Ocean, while emphasizing that air-seawater exchange plays an important role in air-sea interactions in the open ocean.

Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons: Sources, Quantification, Incidence, Toxicity, and Fate in Soil—A Review Study

The genotoxicity, mutagenesis, and carcinogenic effects of polycyclic aromatic hydrocarbon (PAH) derivatives may exceed the parent PAHs. However, their influence on the soil environment has not been explored to a large extent. Oxygenated polycyclic aromatic hydrocarbons (OPAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) are typical polar substituted compounds. We offer a review of the literature on the sources, quantification, incidence, toxicity, and transport of these compounds in soil. Although their environmental concentrations are lower than those of their parent compounds, they exert higher toxicity. Both types of substances are basically related to carcinogenesis. OPAHs are not enzymatically activated and can generate reactive oxygen species in biological cells, while NPAHs have been shown to be mutagenic, genotoxic, and cytotoxic. These compounds are largely derived from the transformation of PAHs, but they behave differently in soil because of their higher molecular weight and dissimilar adsorption mechanisms. Therefore, specialized knowledge of model derivatives is required. We also made recommendations for future directions based on existing research. It is expected that the review will trigger scientific discussions and provide a research basis for further study on PAH derivatives in the soil environment.

Meteorological dependence, source identification, and carcinogenic risk assessment of PM2.5-bound Polycyclic Aromatic Hydrocarbons (PAHs) in high-traffic roadside, urban background, and remote suburban area

The Polycyclic Aromatic Hydrocarbons (PAHs) bound to ambient fine Particular Matter (PM2.5) are currently drawing a lot of attention due to their adverse health effects increasing lung cancer risk in humans. In this study, The PM2.5 samples were collected by high volume air samplers simultaneously from three different sites (high-traffic roadside, urban background, and remote suburban) in Tehran, Iran during warm and cold seasons (from July 2018 to March 2019), and 16 PAHs were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Unlike previous studies, a remote suburban area was chosen so as to observe the spatial differentiation in PM2.5-bound PAH characteristics. In high-traffic roadside site, the average concentration of total PM2.5-bound PAHs (ƩPAHs) was 3.7 times the concentration value in remote suburban area. Average (ƩPAHs) ranged from 5.54 ng/m3 for remote suburban area to 20.67 ng/m3 for high-traffic roadside site. In all sites, seasonal trends of PAH concentrations elucidated high concentrations in the cold season and low concentrations in the warm season. Correlation analysis between ƩPAHs and atmospheric factors (meteorology parameters and criteria air pollutants) indicated the heterogeneous processes play an important role in the level of PAHs. The results of diagnostic ratio (DR) analysis disclosed that the dominant source of PM2.5-bound PAHs was the combustion of liquid fossil fuels. Despite the fact that incremental lifetime cancer risk (ILCR) via inhaling PM2.5-bound PAHs varied significantly in high-traffic roadside site and remote suburban site, its value was beyond the acceptable risk level in both sites. Our results suggested that effective regulations are needed to monitor PAHs concentrations and reduce PAHs emissions from liquid fossil fuel combustion so as to mitigate the potential carcinogenic risk of PAHs in ambient air.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-022-00821-2.

Is Poland at risk of urban road dust? Comparison studies on mutagenicity of dust

Depopulation concerns many polish cities, with the exception of a few metropolises such as Wrocław (Lower Silesia) and Katowice (Upper Silesia) where investments are growing and therefore more humans are exposed to urban environmental pollution. Accumulation of toxic substances on road surfaces is a major global challenge requiring methods of assessing risk that initiate the proper management strategies. In this study urban road dust (URD) has been collected at seventeen sites in Lower and Upper Silesia regions in Poland renowned for their elevated level of pollution. The aim of the study was: (i) to determine PAH concentration in URD in both regions with the identification of their possible sources based on diagnostic ratio; (ii) to assess possible mutagenic effects of URD with the application of Ames test (Salmonella assay); (iii) to define a possible carcinogenic risk related to URD in both studied regions. We found that the total PAH content of collected URD samples ranged from 142.4 to 1349.4 ng g^-1. The diagnostic ratio of PAHs in URD for all studied sites showed that pyrogenic combustion predominated indicating traffic-related and biomass sources of pollution. The Ames assay, which has never been used in studies of URD in Poland, demonstrated that in both regions, URD samples (from eight sites), were characterised by the highest mutagenicity values. Additionally, Incremental Lifetime Cancer Risk (ILCR) values, based on PAH content only, were between 10 and 6 to 10-4 indicating potential risk of cancer. Reassuming, humans in both agglomerations are exposed to factors or compounds with carcinogenic properties which may have an adverse health effect through the urban road dust mainly due to vehicular traffic, heating systems and industrial activities.

Health Risk Assessment of Inhalation Exposure to Airborne Particle-Bound Nitrated Polycyclic Aromatic Hydrocarbons in Urban and Suburban Areas of South China

Airborne particulates (PM_2.5 and TSP) were collected from outdoor and indoor areas at urban (Haizhu District) and suburban (Huadu District) sites from 2019 to 2020 in Guangzhou. Three nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) in the airborne particulates were identified by a gas chromatograph equipped with a triple-quadrupole mass spectrometer. In the Haizhu District and Huadu District, the nitro-PAH concentrations in PM_2.5 and TSP did not show a significant decrease from winter to summer. From 2019 to 2020, the difference in the average concentration of nitro-PAHs in PM_2.5 and TSP in Guangzhou was relatively low and had no statistical significance. The diagnostic ratios of 2-nitrofluorene (2-NF)/1-nitropyrene (1-NP) in TSP are less than five, while for 2-NF/1-NP in outdoor PM_2.5 in the summer of 2019 and 2020 are more than five, which indicates that nitro-PAHs in the atmospheric PM_2.5 in Guangzhou during summer mainly originated from the secondary formation of atmospheric photochemical reactions between parent PAHs and oxidants (·OH, NO₃, and O₃). 9-Nitroanthracene (9-NT) made the most significant contribution to the total nitro-PAH concentration. The incremental lifetime cancer risks (ILCRs) of nitro-PAHs in PM_2.5 and TSP by inhalation exposure indicated low potential health risks in the urban-suburban of Guangzhou.

Burkholderia vietnamiensis G4 as a biological agent in bioremediation processes of polycyclic aromatic hydrocarbons in sludge farms

Polycyclic aromatic hydrocarbons (PAHs) are one of the main pollutants generated by the refining and use of oil. To search bioremediation alternatives for these compounds, mainly in situ, considering the biotic and abiotic variables that affect the contaminated sites is determinant for the success of bioremediation techniques. In this study, bioremediation strategies were evaluated in situ, including biostimulation and bioaugmentation for 16 priority PAHs present in activated sludge farms. B. vietnamiensis G4 was used as a biodegradation agent for bioaugmentation tests. The analyses occurred for 12 months, and temperature and humidity were measured to verify the effects of these factors on the biodegradation. We used the technique GC-MS to evaluate and quantify the degradation of PAHs over the time of the experiment. Of the four treatments applied, bioaugmentation with quarterly application proved to be the best strategy, showing the degradation of compounds of high (34.4% annual average) and low (21.9% annual average) molecular weight. A high degradation rate for high molecular weight compounds demonstrates that this technique can be successfully applied in bioremediation of areas with compounds considered toxic and stable in nature, contributing to the mitigation of impacts generated by PAHs.

Predictive Models of Gas/Particulate Partition Coefficients (KP) for Polycyclic Aromatic Hydrocarbons and Their Oxygen/Nitrogen Derivatives

Polycyclic aromatic hydrocarbons (PAHs) and their oxygen/nitrogen derivatives released into the atmosphere can alternate between a gas phase and a particulate phase, further affecting their environmental behavior and fate. The gas/particulate partition coefficient (KP) is generally used to characterize such partitioning equilibrium. In this study, the correlation between log KP of fifty PAH derivatives and their n-octanol/air partition coefficient (log KOA) was first analyzed, yielding a strong linear correlation (R2 = 0.801). Then, Gaussian 09 software was used to calculate quantum chemical descriptors of all chemicals at M062X/6-311+G (d,p) level. Both stepwise multiple linear regression (MLR) and support vector machine (SVM) methods were used to develop the quantitative structure-property relationship (QSPR) prediction models of log KP. They yield better statistical performance (R2 > 0.847, RMSE < 0.584) than the log KOA model. Simulation external validation and cross validation were further used to characterize the fitting performance, predictive ability, and robustness of the models. The mechanism analysis shows intermolecular dispersion interaction and hydrogen bonding as the main factors to dominate the distribution of PAH derivatives between the gas phase and particulate phase. The developed models can be used to predict log KP values of other PAH derivatives in the application domain, providing basic data for their ecological risk assessment.

Assessment of the inhalation exposure and incremental lifetime cancer risk of PM2.5 bounded polycyclic aromatic hydrocarbons (PAHs) by different toxic equivalent factors and occupancy probability, in the case of Xi'an

Polycyclic aromatic hydrocarbons (PAHs) are widespread toxic pollutants in the atmosphere and have attracted much attention for decades. In this study, we compared the health risks of PAHs based on different toxic equivalent factors (TEFs) in a heavily polluted area during heating and non-heating periods. We also pay attention to occupancy probability (OP) in different polluted areas. The results showed that there were big differences for calculations by different TEFs, and also by OP or not. Age groups except adults were all lower calculated by OP than not. The sensitivity analysis results on the incremental lifetime cancer risks (ILCR) for population groups by Monte Carlo simulation identified that the cancer slope factor extremely affected the health risk assessment in heating periods, followed by daily inhalation exposure levels. However, daily inhalation exposure levels have dominated the effect on the inhalation ILCR and then followed by the cancer slope factor in non-heating periods. The big differences by different calculations investigated that it is important to set up the correlations between the pollution level and health risks, especially for the longtime health assessment.

The seasonal variation, characteristics and secondary generation of PM2.5 in Xi'an, China, especially during pollution events

As an important central city in western China, Xi'an has the worst atmospheric pollution record in China and many measures have been taken to improve the air quality in the past few years. In this study, PM_2.5 samples were collected across four seasons from 2017 to 2018 in Xi'an. Organic carbon and elemental carbon, water soluble ions, and elements were monitored to assess the air quality. The average annual PM_2.5 concentration was (134.9 ± 48.1 μg/m³), with the highest concentration in winter (188.8 ± 93.2 μg/m³), and lowest concentration in summer (71.2 ± 12.1 μg/m³). The secondary generation of sulfate (SO₄^2-) and nitrate (NO₃^-) was strong in spring, and secondary organic carbon (SOC) was formed in all seasons. The compositions of PM_2.5 changed greatly during a sandstorm occurred and the Spring Festival. The sandstorm played a positive role in removing local pollutant NO₃^-, but also increased the concentration of SO₄^2-, however both the concentration of SO₄^2- and NO₃^- greatly increased by secondary generation during Spring Festival. Potential source analysis showed that during the sandstorm, pollutants were transported over a long distance from the northwest of China, whereas it was mainly from the local and surrounded emissions during the Spring Festival. Except Ca²⁺ and geological dust (GM), the other components in PM_2.5 increased significantly on the day of the Spring Festival. During sampling time in Xi'an, the positive matrix factorization (PMF) model analysis showed that PM_2.5 mainly came from vehicle emission, coal combustion, and biomass burning.

Atmospheric occurrences of nitrated and hydroxylated polycyclic aromatic hydrocarbons from typical e-waste dismantling sites

Primitive electronic waste (e-waste) dismantling activities have been shown to be an important emissions source for a variety of toxic organic compounds, including carcinogenic polycyclic aromatic hydrocarbons (PAHs). Previous studies have found that some nitrated PAHs (NPAHs) are more toxic than their parent PAHs, however, little attention has been paid to the formation of PAH derivatives during e-waste processing and there is a lack of comprehensive data from field observations. In this study, the spatial distribution, temporal trends and atmospheric fate of NPAHs and hydroxylated PAHs (OH-PAHs) were investigated at typical e-waste dismantling sites, with monitoring data collected over three consecutive years. Compared to background levels, higher levels of NPAHs and OH-PAHs were found in air samples from an e-waste dismantling industrial park, with their seasonal and annual changes shown to be affected by e-waste dismantling activities. Atmospheric PM_2.5 particles were found to have high relative abundances of NPAHs (76.9%-95.1%) and OH-PAHs (73.3%-91.6%), with particle-bound concentrations ranging from 20.1 to 88.8 and 37.1 to 107 pg m^-3, respectively. The most abundant NPAH isomers were found to be 9-Nitroanthracene and 2-Nitrofluoranthene, while OH-PAH isomers containing 2-4 rings were predominant. Source identification was performed based on the specific diagnostic ratios of NPAH isomers, confirming that NPAH and OH-PAH emissions have multiple sources, including emissions related to the e-waste dismantling process, atmospheric photochemical reactions and traffic emissions. Further research on the fate of such derivatives and their potential use as markers for source identification, is urgently required.

Atmospheric chemistry and cancer risk assessment of Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs over a semi-arid site in the Indo-Gangetic plain

Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs were collected over a year at a traffic dominated site in Agra, to determine the dominant partitioning mechanism. During the entire sampling period, total PAHs and Nitro-PAHs were 3465 ± 3802 and 26.1 ± 25.9 ng m^-3 respectively. The gas-particle partitioning behavior of PAHs was studied by applying the Pankow model, Absorption model, and Dual model. Amongst all the partitioning models, the Dual model fits well and indicates that the partitioning of PAHs at the traffic site in Agra depends on both the physical adsorption of PAHs on the Total Suspended Particulate (TSP) surface and absorption of PAHs into the organic layer present on the TSP surface. Pankow model indicates that PAHs are emitted from the source close to the sampling point and due to this PAHs do not get enough time to get partitioned in between both the phases. Incremental lifetime Cancer Risk (ILCR) shows that adults and children are more prone to cancer risk in comparison to infants for both PAHs and Nitro-PAHs. Cancer risk by inhalation was minimum in comparison to both ingestion and dermal exposure. Nitro-PAHs in the particulate phase were high enough to exceed the minimum permissible limit (10^-6) of causing cancer by ingestion and dermal exposure.

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.

Temporal profiles, source analysis, and health risk assessments of parent polycyclic aromatic hydrocarbons (PPAHs) and their derivatives (NPAHs, OPAHs, ClPAHs, and BrPAHs) in PM2.5 and PM1.0 from the eastern coastal region of China: Urban coastal area versus coastal background area

The eastern coastal region of China is the area with the highest emission of PAHs in China. Therefore, understanding the sources and health risk of parent polycyclic aromatic hydrocarbons (PPAHs) and their derivatives in eastern coastal cities of China is the main basis for air pollution control. In this study, we measured the concentrations of 18 parent PAHs, 17 nitrated PAHs, 7 oxygenated PAHs, 8 chlorinated PAHs, and 13 brominated PAHs in PM_1.0 and PM_2.5 samples collected at an urban coastal city site and a coastal background site in 2019. We analyzed the temporal distribution, molecular composition, and sources and performed health risk assessments for both winter and summer samples. The average concentration of the PPAHs and their derivatives (all 63 compounds combined) in the PM_1.0 samples accounted for 75.57% of the PAHs concentration in PM_2.5 samples. The average concentration of PM_2.5- and PM_1.0- bound PPAHs in winter was 114.70 times higher than in summer, and their derivatives was 27.51 times. Both the combined concentrations of the 18 PPAHs and the combined concentrations of the 45 derivatives were higher in the coastal city compared to the background site during the winter (1.90 and 1.48 times, respectively), but they were comparable during the summer. The positive matrix factorization analysis indicated that the compounds mainly originated from coal/biomass combustion, industrial sources, vehicle emissions, and secondary formation. In addition, the concentration-weighted trajectories model revealed that the PAHs were mainly emitted locally in Shandong Province and surrounding areas, such as Hebei Province, Henan Province, and Bohai Sea. The compounds 1-NPYR, 2+9-BrPHE, 9,10-Cl2PHE, and 1-ClPYR dominantly contributed to the derivatives of TEQ during the winter due to their high concentrations or the high TEFs of these compounds.

Temporal Trend of Polycyclic Aromatic Hydrocarbons in Atmosphere: A Case Study within 24 h after Snowfall

Based on air samples within 24 h after snowfall, gaseous and particulate concentrations of 16 priority PAHs were obtained, which provided a good opportunity to study the temporal trend of atmospheric PAHs. An obvious temporal trend with atmospheric concentration was observed, which was mainly influenced by emission sources. It was found that the maximum concentration (Σ₁₆PAHs) was 272.8 ng/m³, appeared in the rush hour of traffic. To the contrary, the minimum concentration was 82.39 ng/m³ at the period with the least anthropogenic activities. The values of particle-phase fraction[Formula: see text]) and G/P partitioning quotient (log K _P) were increased along with molecular weight of PAHs. However, for individual PAHs, the differences with [Formula: see text] and log K _P were not obvious within 24 h. Furthermore, similar statistically significant positive correlations were found between log K _P and log K _OA among different periods. According to the short sampling program, chemical properties should be the major influencing factor for the temporal trend of G/P partitioning. The results of the case study provided new insights into the research field of G/P partitioning of PAHs.

Application of gas chromatographic retention times to determine physicochemical properties of nitrated, oxygenated, and parent polycyclic aromatic hydrocarbons

Nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) are receiving attention because of their high toxicity compared with parent PAHs. However, the experimental data of their physicochemical properties has been limited. This study proposed the gas chromatographic retention time (GC-RT) technique as an effective alternative one to determine octanol-air partition coefficients (K_OA) and sub-cooled liquid vapor pressures (P_L) for 11 NPAHs, 10 OPAHs, and 19 parent PAHs. The slopes and intercepts of the linear regressions between temperature versus K_OA and P_L were provided and can be used to estimate K_OA and P_L for the 40 targeted compounds at any temperature. The internal energies of phase transfer (ΔU_OA) and enthalpies of vaporization (ΔH_L) for all targeted compounds were also calculated using the GC-RT technique. High-molecular-weight compounds may release or absorb higher heat energy to transform between different phases. NPAHs and OPAHs had a non-ideal solution behavior with activity in octanol (γ_oct) in the range of 19-53 and 18-1,078, respectively, which is larger than the unity threshold. A comparison among four groups of PAH derivatives showed that a functional group (nitro-, oxygen-, chloro-, and bromo-) in PAH derivatives increased γ_oct for corresponding parent PAHs by tens (mono-group) to hundreds of times (di-group). This study suggests that the GC-RT method is applicable for indirectly measuring the physicochemical properties of various groups of organic compounds.

Potential Risks of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and Heavy Metals from Inland and Marine Directions for a Marine Background Site in North China

Ambient PM_2.5-bound ions, OC, EC, heavy metals (HMs), 18 polycyclic aromatic hydrocarbons (PAHs), 7 hopanes, and 29 n-alkanes were detected at Tuoji Island (TI), the only marine background atmospheric monitoring station in North China. The annual PM_2.5 average concentration was 47 ± 31 μg m^-3, and the average concentrations of the compositions in PM_2.5 were higher in cold seasons than in warm seasons. The cancer and non-cancer risks of HMs and PAHs in cold seasons were also higher than in warm seasons. BaP, Ni, and As dominated the ∑HQ (hazard quotient) in cold seasons, while the non-carcinogenic risk in warm seasons was mainly dominated by Ni, Mn, and As. The ILCR (incremental lifetime cancer risk) values associated with Cr and As were higher in the cold season, while ILCR-Ni values were higher in the warm season. The backward trajectory was calculated to identify the potential directions of air mass at TI. Through the diagnostic ratios of organic and inorganic tracers, the sources of particulate matter in different directions were judged. It was found that ship emissions and sea salt were the main sources from marine directions, while coal combustion, vehicles emissions, industrial process, and secondary aerosols were the main source categories for inland directions. In addition, potential HM and PAH risks from inland and marine directions were explored. The non-cancerous effects of TI were mainly affected by inland transport, especially from the southeast, northwest, and west-northwest. The cancerous effects of TI were mainly simultaneously affected by the inland direction and marine direction of transport.

NPAHs and OPAHs in the atmosphere of two central European cities: Seasonality, urban-to-background gradients, cancer risks and gas-to-particle partitioning

Derivatives of polycyclic aromatic hydrocarbons (PAHs) such as nitrated- and oxygenated-PAHs (NPAHs and OPAHs) could be even more toxic and harmful for the environment and humans than PAHs. We assessed the spatial and seasonal variations of NPAHs and OPAHs atmospheric levels, their cancer risks and their gas-to-particle partitioning. To this end, about 250 samples of fine particulate matter (PM2.5) and 50 gaseous samples were collected in 2017 in central Europe in the cities of Brno and Ljubljana (two traffic and two urban background sites) as well as one rural site. The average particulate concentrations were ranging from below limit of quantification to 593 pg m-3 for Σ9NPAHs and from 1.64 to 4330 pg m-3 for Σ11OPAHs, with significantly higher concentrations in winter compared to summer. In winter, the particulate levels of NPAHs and OPAHs were higher at the traffic site compared to the urban background site in Brno while the opposite was found in Ljubljana. NPAHs and OPAHs particulate levels were influenced by the meteorological parameters and co-varied with several air pollutants. The significance of secondary formation on the occurrence of some NPAHs and OPAHs is indicated. In winter, 27-47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The gas-particle partitioning of NPAHs and OPAHs was influenced by their physico-chemical properties, the season and the site-specific aerosol composition. Three NPAHs and five OPAHs had higher particulate mass fractions at the traffic site, suggesting they could be primarily emitted as particles from vehicle traffic and subsequently partitioning to the gas phase along air transport. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk.

Fine particle-bound PAHs derivatives at mountain background site (Mount Tai) of the North China: Concentration, source diagnosis and health risk assessment

Ten nitrated polycyclic aromatic hydrocarbons (nPAHs) and 4 oxygenated polycyclic aromatic hydrocarbons (oPAHs) in fine particulate matter (PM_2.5) samples from Mount Tai were analyzed during summer (June to August), 2015. During the observation campaign, the mean concentration of total nPAHs and oPAHs was 31.62 pg/m³ and 0.15 ng/m³, respectively. Two of the monitored compounds, namely 9-nitro-anthracene (9N-ANT) (6.86 pg/m³) and 9-fluorenone (9FO) (0.05 ng/m³) were the predominant compounds of nPAHs and oPAHs, respectively. The potential source and long-range transportation of nPAHs and oPAHs were investigated by the positive matrix factorization (PMF) method and the potential source contribution function (PSCF) methods. The results revealed that biomass/coal burning, gasoline vehicle emission, diesel vehicle emission and secondary formation were the dominant sources of nPAHs and oPAHs, which were mainly from Henan province and Beijing-Tianjin-Hebei region and Bohai sea. The incremental life cancer risk (ILCR) values were calculated to evaluate the exposure risk of nPAHs and oPAHs for three group people (infant, children and adult), and the values of ILCR were 7.02 × 10^-10, 3.49 × 10^-9 and 1.41 × 10^-8 for infant, children and adults, respectively. All these values were lower than the standard of EPA (Environmental Protection Agency) (<10^-6), indicating acceptable health risk of nPAHs and oPAHs.

Occurrence, fates, and carcinogenic risks of substituted polycyclic aromatic hydrocarbons in two coking wastewater treatment systems

This paper reports for the first time the occurrence, fates, and carcinogenic risks of 20 substituted polycyclic aromatic hydrocarbons (SPAHs) and 16 priority PAH species in two coking wastewater treatment plants (WWTPs) (plant E and central WWTP). The measured total concentrations of PAHs and SPAHs in raw wastewater of coking plant E were 3700 and 1200 μg·L^-1, respectively, with naphthalene (1400 μg·L^-1), and fluoranthene (353 μg·L^-1) as dominant PAH species and 2-methylnaphthalene (167 μg·L^-1), anthraquinone (133 μg·L^-1), and 1-methylnaphthalene (132 μg·L^-1) as dominant SPAHs. For the 11 methyl-PAHs (MPAHs), 4 oxygenated-PAHs (OPAHs), and 5 nitrated-PAHs (NPAHs) investigated, the biological wastewater treatment process removed 98.6% MPAHs, 83.9% OPAHs, and 89.1% NPAHs. Mass balance analysis result revealed that transformation was the major mechanism to remove low-molecular-weight (LMW) MPAHs (59.9-77.3%), a large part of OPAHs, including anthraquinone, methylanthraquinone, and 9-fluorenone (46.7-49.6%), and some NPAHs, including 2-nitrofluorene and 9-nitroanthrancene (52.9-59.1%). Adsorption by activated sludge mainly accounted for removing high-molecular-weight (HMW) SPAHs (59.6-71.01%). The relatively high concentrations of SPAHs in excess sludge (15,000 μg·g^-1) and treated effluent (104 μg·L^-1) are of great concern for their potential adverse ecological impacts. SPAHS exhibited similar behaviors in central WWTP, though the influent concentrations were much lower. The concentration levels of SPAHs in the ambient air of coking plant E and central WWTP may also pose potential lung cancer risks (LCR) to the workers through inhalation, where all studied SPAHs except 3-nitrofluoranthene and 7-nitrobenz[a]anthracene exceeded the acceptable cancer risk standards (>10^-6) recommended by U.S EPA. This study could help identify the ecological and healthy risks during coking wastewater treatment and provide useful information for policy-making.

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.

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.

Urinary metabolites of polycyclic aromatic hydrocarbons after short-term fine particulate matter exposure: A randomized crossover trial of air filtration

Research on the relationship between short-term exposure to fine particulate matter (PM_2.5) and urinary metabolites of polycyclic aromatic hydrocarbons (PAHs) is sparse in the nonoccupationally exposed populations. A quasi-experimental observation of haze events nested within a randomized crossover trial of alternative 1-week real or sham indoor air filtration was conducted to evaluate the associations of urinary monohydroxy-PAHs (OH-PAHs) with short-term exposure to PM_2.5 and PM_2.5-bound PAHs. The study was conducted among 57 healthy college students in Beijing, China. PM_2.5-bound PAHs and urinary OH-PAHs were quantified using gas chromatography coupled with a triple-quadrupole tandem mass spectrometer. Linear mixed-effect models were applied to evaluate the association of urinary OH-PAHs with time-weighted personal PM_2.5 and PM_2.5-bound PAHs, controlling for potentially confounding variables. The results demonstrated that air filtration could markedly reduce external exposure to PM_2.5 and PM_2.5-bound parent, nitrated, and oxygenated PAHs. In the intervention trial, the urinary concentrations of 2-hydroxyfluorene (2-OH-FLU) and 9-hydroxyphenanthrene (9-OH-PHE) were elevated significantly by 16.5% (95% CI, 2.1%, 33.1%) and 37.9% (95% CI, 8.4%, 75.4%), respectively, in association with a doubling increase in personal PM_2.5 exposure. Urinary 9-OH-PHE was also significantly positively associated with the increase in the sum of PM_2.5-bound parent PAHs. Furthermore, the levels of urinary OH-PAHs such as 2-OH-FLU and 9-OH-PHE in the haze events were elevated by 31.1% (95% CI, 8.7%, 53.4%) and 73.5% (95% CI, 16.0%, 131.0%), respectively, in association with a doubling increase in personal PM_2.5 exposure. The findings indicated that urinary 2-OH-FLU and 9-OH-PHE could serve as potential internal exposure biomarkers for assessing short-term PM_2.5 exposure in nonoccupational populations.

Polycyclic aromatic compounds (PAHs, oxygenated PAHs, nitrated PAHs, and azaarenes) in air from four climate zones of China: Occurrence, gas/particle partitioning, and health risks

Polycyclic aromatic compounds (PACs) such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives [oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs), and azaarenes (AZAs)] are toxic and ubiquitous air pollutants. In this study, the concentrations of these PACs were determined in air obtained in spring and autumn of 2012 from urban and rural areas of the Tibetan Plateau, temperate, subtropical, and tropical climate zones in China. Average concentrations (gaseous + particulate) of ∑29PAHs, ∑15OPAHs, ∑11NPAHs, and ∑4AZAs were 928 ± 658, 54 ± 45, 5.3 ± 4.4, 14 ± 11 ng m^-3 and 995 ± 635, 67 ± 38, 8.4 ± 6.1, 24 ± 16 ng m^-3 in spring and autumn, respectively. Various C fractions and latitude correlated significantly with the concentrations and ratios of PACs. The slopes of the regression of gas-particle partition coefficients (K_p) of PACs on their sub-cooled liquid vapor pressures (P_L⁰), indicated both adsorption and absorption to total suspended particles (TSP) for PAHs, OPAHs, and NPAHs in the four studied climatic zones. This result was further supported by comparing the fractions of PACs in TSP calculated from field data with those predicted by the Junge-Pankow adsorption and K_OA absorption models. The concentration ratios of most OPAHs or NPAHs to their parent PAHs and of benzo[e]pyrene/benzo[a]pyrene were higher in autumn than in spring and increased with remoteness from point sources. This suggests enhanced secondary formation of PAH derivatives due to the elevated photochemical activity in autumn and longer ageing of air and associated transformation of PACs during their long-distance transport from source regions (urban sites) to rural sites. Lifetime lung cancer risk estimated from PACs ranged from 0.8 ± 0.6 to 3.1 ± 1.0 (×10^-3), exceeding the value (10^-5) recommended by the WHO. Gaseous PACs contributed substantially to the estimated cancer risks and their contributions increased with decreasing latitude in China.

Human Health Assessment of Sixteen Priority Polycyclic Aromatic Hydrocarbons in Contaminated Soils of Northwestern Algeria

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental organic contaminants generated by incomplete combustion of organic materials that are widely distributed in soils.

OBJECTIVES

This study represents the first attempt to examine the health toxicity of 16 detected PAHs in contaminated soil, via different exposure pathways to populations in northwestern Algeria.

METHODS

The toxicity equivalency quotients (TEQ) of PAHs were evaluated. The carcinogenic risk assessment of incremental lifetime cancer risk (ILCR) from ingestion, inhalation, and dermal exposure pathways to each PAH in soil are described.

RESULTS

Incremental lifetime cancer risk values were in the upper limit of the tolerable range (10^-6-10^-4) for adults and children. The total cancer risk of PAH-contaminated soils for children, adolescents and adults was 2.48×10^-5, 2.04×10^-5 and 3.12×10^-5mg.kg^-1d^-1, respectively. The highest potential cancer risks were identified for adults and children, with adolescents having the lowest risks. Across exposure pathways, the dermal contact and ingestion pathways had the greatest contributions to the carcinogenic risk of human exposure to PAHs.

CONCLUSIONS

Further research and guidelines are needed for risk assessments of PAHs in agricultural, residential/urban, and industrial areas, and further risk assessments should include risks posed by exposure through air.

COMPETING INTERESTS

The authors declare no competing financial interests.

Air pollution increases human health risks of PM2.5-bound PAHs and nitro-PAHs in the Yangtze River Delta, China

Identifying the nature and extent of atmospheric PM_2.5-bound toxic organic pollutants is beneficial to evaluate human health risks of air pollution. Seasonal observations of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in the Yangtze River Delta (YRD) were investigated, along with criteria air pollutants and meteorological parameters. With the elevated PM_2.5 level, the percentage of 4-ring PAHs and typical NPAH including 3-Nitrobiphenyl (3-NBP) and 2-Nitrofluoranthene (2-NFLT) increased by 19-40%. PM_2.5-bound 2-NFLT was positively correlated with O₃ and NO₂, suggesting the contribution of atmospheric oxidation capacity to enhance the secondary formation of NPAHs in the atmosphere. Positive matrix factorization (PMF) analysis indicated that traffic emissions (44.9-48.7%), coal and biomass combustion (27.6-36.0%) and natural gas and volatilization (15.3-27.5%) were major sources of PAHs, and secondary formation (39.8-53.8%) was a predominant contributor to total NPAH concentrations. Backward trajectory analysis showed that air masses from North China transported to the YRD region increased PAH and NPAH concentrations. Compare to clean days, the BaP equivalent concentrations of total PAHs and NPAHs during haze pollution days were enhanced by 10-25 and 2-6 times, respectively. The Incremental Lifetime Cancer Risks (ILCRs) of PAHs by inhalation exposure also indicated high potential health risks in the YRD region. The results implied that the health risks of PM_2.5-bound PAHs and NPAHs could be sharply enhanced with the increase of PM_2.5 concentrations.

Detoxification modification of coal-tar pitch by ultraviolet & microwave radiation-enhanced chemical reaction and toxicity evaluation by chemical index and cytotoxicity assay in vitro

Although coal tar pitch (CTP) has a large yield in China, its large-scale and effective utilization is significantly hindered because of existing and possibly releasing polycyclic aromatic hydrocarbons (PAHs). Therefore, it is an imminent problem how to prepare an environmentally friendly CTP by detoxification modification. In the investigation, a typical CTP was subjected to structural characterization via solid-state ¹³C NMR and gas chromatograph/mass spectrometer, which confirmed the existence of dominant PAHs such as fluoranthene, pyrene, as well as benzo[a]pyrene, and few heterocyclic compounds. Subsequently, the CTP was modified using 10-undecenal via alkylation reaction enhanced by ultraviolet & microwave radiation. Compared with the original CTP, the total content of 16 toxic PAHs in the modified CTP decreased with a reduction efficiency of above 90%. According to different environmental standards, toxic equivalent quotient of CTP after modification was reduced by above 90%. In order to veritably and fully evaluate the toxicity of CTP, a living vascular smooth muscle cell (A-10 cell) in vitro was used in the cell counting kit-8 assay. The viability of A-10 cell was always higher when exposed to modified CTP than the original CTP. These results powerfully indicated that the enhanced modification was actually effective and efficient for reducing the toxicity of CTP.

Nitrated and parent PAHs in the surface water of Lake Taihu, China: Occurrence, distribution, source, and human health risk assessment

Nitrated polycyclic aromatic hydrocarbons (NPAHs) have toxic potentials that are higher than those of their corresponding parent polycyclic aromatic hydrocarbons (PAHs) and thus have received increasing attention in recent years. In this study, the occurrence, distribution, source, and human health risk assessment of 15 NPAHs and 16 PAHs were investigated in the surface water from 20 sampling sites of Lake Taihu during the dry, normal, and flood seasons of 2018. The ΣPAH concentrations ranged from 255 to 7298 ng/L and the ΣNPAH concentrations ranged from not-detected (ND) to 212 ng/L. Among the target analytes, 2-nitrofluorene (2-nFlu) was the predominant NPAH, with a detection frequency ranging from 85% to 90% and a maximum concentration of 56.2 ng/L. The three-ringed and four-ringed NPAHs and PAHs comprised the majority of the detected compounds. In terms of seasonal variation, the highest levels of the ΣNPAHs and ΣPAHs were in the dry season and flood season, respectively. Diagnostic ratio analysis indicated that the prime source of NPAHs was direct combustion, whereas in the case of PAHs the contribution was predominantly from a mixed pattern including pollution from unburned petroleum and petroleum combustion. The human health risk of NPAHs and PAHs was evaluated using a lifetime carcinogenic risk assessment model. The carcinogenic risk level of the targets ranged from 2.09 × 10^-7 to 5.75 × 10^-5 and some surface water samples posed a potential health risk.

Environment impact and probabilistic health risks of PAHs in dusts surrounding an iron and steel enterprise

Dust can be regarded as environmental medium that indicates the level and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) coming from different pollution sources. In this study, samples including road dust, roof dust, and bare soil near an iron and steel enterprise (ISE) in Laiwu city of North China were collected. To assess the environment impact, atmosphere particulates and one flue dust from a coking plant were simultaneously sampled. Sixteen USEPA PAHs were detected quantitatively by Gas Chromatography Mass Spectrometry (GC-MS). A laser particle size analyzer was used to obtain the grain size of the dust particle samples. The results showed that PAH concentrations displayed great variability in the dust samples. The ∑₁₆PAHs concentration was found to be between 0.460 and 46.970 μg/g (avg ± sd 10.892 ± 1.185 μg/g) in road dust, between 0.670 and 17.140 μg/g (avg ± sd 6.751 ± 0.692 μg/g) in roof dust, and 13.990 ± 1.203 μg/g in bare soil. In the environment atmosphere sites, the ∑₁₆ PAHs value in PM_2.5 constituted a very large proportion of PM₁₀, indicating that PAHs in finer particle sizes should be given greater emphasis. The ∑₁₆PAHs concentration was relatively high in the area close to the ISE because of the great impact of the ISE industrial activities. PAH concentration curves were similar, and the most abundant individual PAHs in the atmosphere sites were BbF, BkF, and Flu, and BbF, BkF, and Chry in dusts. Toxicity analysis revealed that PAHs with four rings, including carcinogenic PAHs, were the dominant pollutants in the studied area. The toxic equivalency value (TEQ_BaP), the carcinogenic health risk assessment value recommended by the US EPA, was calculated for seven carcinogenic PAHs, revealing that they account for more than 93.0% of the total TEQ_Bap of the 16 PAHs and indicating the major toxic equivalent concentration contributor. Incremental lifetime cancer risk (ILCR) estimation results showed that PAHs tended to bring about great health risks through skin contact, followed by ingestion and inhalation. By comparison, road dust exhibited greater carcinogenic risks than roof dust, and bare soil may undergo heavier pollution. Therefore, the results of this study would be helpful in the effort to understand the PAHs pollution from the steel industry, which will provide some guidance for the probabilistic assessment of local health risks.

A 150-year record of black carbon (soot and char) and polycyclic aromatic compounds deposition in Lake Phayao, north Thailand

An improved understanding of the historical variation in the emissions and sources (biomass burning, BB vs. fossil fuel, FF combustion) of soot and char, the two components of black carbon (BC), and polycyclic aromatic compounds (PACs) may help in assessing the environmental effects of the Atmospheric Brown Cloud (ABC) in SE Asia. We therefore determined historical variations of the fluxes of soot, char, and PACs (24 polycyclic aromatic hydrocarbons (PAHs), 12 oxygenated PAHs (OPAHs), and 4 azaarenes) in a dated sediment core (covering the past ∼150 years) of Phayao Lake in Thailand. The soot fluxes have been increasing in recent times, but at a far lower rate than previously estimated based on BC emission inventories. This may be associated with a decreasing BB contribution as indicated by the decreasing char fluxes from old to young sediments. The fluxes of high- and low-molecular-weight (HMW and LMW) PAHs, OPAHs, and azaarenes all sharply increased after ∼1980, while the ΣLMW-/ΣHMW-PAHs ratios decreased, further supporting the reduction in BB contribution at the expense of increasing FF combustion emissions. We also suggest that the separate record of char and soot, which has up to now not been done in aerosol studies, is useful to assess the environmental effects of ABC because of the different light-absorbing properties of these two BC components. Our results suggest that besides the establishment of improved FF combustion technology, BB must be further reduced in the SE Asian region in order to weaken the ABC haze.

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.

Spatial distribution of greenhouse gases (CO2 and CH4) on expressways in the megacity Shanghai, China

Carbon dioxide (CO2) and methane (CH4) are the two major greenhouse gases (GHGs) in the atmosphere that contribute to global warming. Vehicle emissions on expressways cannot be neglected in the megacity Shanghai because oil accounts for 41% of the total primary energy consumption, and the expressway network carries 60% of the total traffic volume. The spatial distributions of CO2 and CH4 concentrations were monitored in situ on the expressways and in road tunnels using a mobile vehicle. The average CO2 and CH4 concentrations were 472.88 ± 34.48 ppm and 2033 ± 54 ppb on the expressways and 1308.92 ± 767.48 ppm and 2182 ± 112 ppb in the road tunnels in Shanghai, respectively. The highest CO2 and CH4 concentrations appeared on the Yan'an Elevated Road and the North-South Elevated Road, respectively, while their lowest values both occurred on the Huaxia Elevated Road passing through the suburban area. The hotspots of CO2 and CH4 were not consistent, suggesting that they have different sources. Tunnels had a "push-pull effect" on GHGs, and the traffic-congested Yan'an East Road Tunnel showed a dramatically increasing trend of GHG concentration from the entrance to the exit. This traffic-congested tunnel could accumulate a very high concentration of GHGs as well as other pollutants, which could introduce unhealthy conditions for both drivers and passengers. Significant correlations between CO2 and CH4 mostly appeared on the expressways and in the tunnels in Shanghai, suggesting the influences of vehicle exhaust. ΔCH4/ΔCO2 (the slope of the linear regression between CH4 and CO2) and the CH4/CO2 ratio could be used as indicators of vehicle exhaust sources because it increases from sources (e.g., road tunnels) to the observatories in the urban area.

Reduction of polycyclic aromatic hydrocarbons (PAHs) emission from household coal combustion using ferroferric oxide as a coal burning additive

Household coal combustion is identified to be the second largest emission source of polycyclic aromatic hydrocarbons (PAHs) in China. In this study, ferroferric oxide (Fe₃O₄) was used as a coal burning additive to reduce PAHs emission from coal combustion in a household coal stove. The results showed that Fe₃O₄ participated in the coal combustion process. The addition of Fe₃O₄ reduced the release of PAHs during the coal combustion process, and could improve the residence capacity of ash residue to these PAHs. Toxic equivalent quantity (TEQ) of PAHs in flue gas from combustion of coal mixed with Fe₃O₄ was less than that from the raw coal combustion. For a typical combustion temperature of 850 °C, the TEQ of PAHs for the mixture of coal and 2.0 wt% Fe₃O₄ decreased 21.98% compared to that for the raw coal. The abundant active surface oxygen species originated from the phase transformation of iron oxides probably accelerated the cracking of PAHs, and hence led to the reduction of PAH emissions and their TEQ. The study could help to develop new technology for reduction of PAHs emission from household coal combustion.

Seasonal variation and gas/particle partitioning of atmospheric halogenated polycyclic aromatic hydrocarbons and the effects of meteorological conditions in Ulsan, South Korea

Atmospheric halogenated polycyclic aromatic hydrocarbons (Halo-PAHs) and parent PAHs were monitored in Ulsan, South Korea for one year (January‒December 2015) to investigate their seasonal patterns, gas/particle partitioning behavior, and the impact of meteorological conditions. The mean concentrations of 24 chlorinated PAHs, 11 brominated PAHs, and 13 parent PAHs in the gaseous and particulate phases were 8.64 and 9.64 pg/m³, 11.6 and 1.62 pg/m³, and 2.17 and 2.40 ng/m³, respectively. Winter had the highest ClPAH and PAH levels, with significant contributions from poly-chlorine groups and high-molecular-weight compounds. However, BrPAHs showed reverse patterns with the highest concentration in summer and the dominant gaseous fraction throughout the year. This finding could be explained by the strong local sources of BrPAHs, related to automobile and petrochemical industries. In contrast, the effects of the temperature inversion layer and atmospheric transport from the outside of Ulsan were more apparent for ClPAHs and PAHs, particularly in winter and spring. Regarding gas/particle partitioning, Halo-PAHs exhibited different seasonal behaviors from those of parent PAHs. The sorption pathway of Halo-PAHs seemed to shift from absorption as the sole dominant mechanism in winter and spring to both adsorption and absorption in summer and fall, while both partitioning mechanisms contributed equally for parent PAHs during the entire year. This study implies that Halo-PAHs and parent PAHs might not share the same atmospheric behavior, possibly due to different characteristics in atmospheric reactions with other chemicals and particle-size distribution. However, there have been limited studies about the formation of Halo-PAHs and their physicochemical properties; hence, further in-depth investigations are of vital importance.

Phase distribution of polycyclic aromatic hydrocarbons and their oxygenated and nitrated derivatives in the ambient air of a Brazilian urban area☆

Air quality in large cities has worsened in recent years as a consequence people's health is directly affected. Among the toxic compounds released to environmental air are polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (nitro-PAHs), and oxygenated PAHs (oxy-PAHs). Performant methods to analyze these compounds is necessary to enable adequate monitoring of air quality. Thus, this manuscript presents the development of a highly sensitive method to analyze PAHs, nitro-PAHs, and oxy-PAHs collected from ambient air (PM_2.5) and the gas phase for a period of one year in the urban area of Belo Horizonte, Brazil. PAHs and their derivatives were extracted by cold fiber solid phase microextraction (CF-SPME) and analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The proposed method allows simultaneous analysis of 16 PAHs, nitro-PAHs and oxy-PAHs, presenting very good limits of detection and quantification, as well as appropriate precision and recovery. The results obtained for the period of one year allowed different studies. The compounds collected simultaneously from gas and particulate phase showed that total concentration of 16 PAHs were higher in the gas phase than in the particulate. On the other hand, nitro-PAHs and oxy-PAHs presented similar concentration in gas and particulate phases. The potential carcinogenicity of PAHs relative to benzo[a]pyrene showed benzo[a]pyrene equivalents of 0.49 ng m^-3. The estimated risk of lifetime lung cancer was 5 × 10^-5. Principal component analysis and diagnostic ratio was applied for source distribution indicating that burning of gasoline, diesel and biomass accounted for the PAHs profile in ambient air samples.