Characterization and carcinogenic risk assessment of polycyclic aromatic and nitro-polycyclic aromatic hydrocarbons in exhaust emission from gasoline passenger cars using on-road measurements in Beijing, China

Emission characteristic, spatial distribution, and health risk of polycyclic aromatic compounds (PAHs, NPAHs, and OPAHs) from light-duty gasoline and diesel vehicles based on on-road measurements

Vehicle exhaust is the primary source of polycyclic aromatic compounds (PACs). Real road tests using a portable vehicle measurement system on light-duty gasoline vehicles and light-duty diesel trucks were conducted to investigate gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and oxy-PAHs (OPAHs) in vehicle exhaust with different emission standards, fuel types, and altitudes. The results showed that with the tightening of emission standards, the overall emission factors (EFs) of PACs decreased. Compared with China V diesel vehicles, the emissions of PAHs, OPAHs, and NPAHs from China VI diesel vehicles were 75.1 %, 84.4 %, and 61.2 % lower, respectively. With a ∼100 m increase in altitude, the EFs of PAHs, OPAHs, and NPAHs of diesel vehicles increased 1.88, 1.92, and 1.59 times due to incomplete combustion. In addition, the EFs of PAHs and OPAHs in gasoline vehicles were lower than those in diesel vehicles. In contrast, the proportion of PAHs with highly toxic components, such as dibenzo[a,h]anthracene (DahA) and benzo[a]pyrene (BaP), and the EFs of gas-phase NPAHs in gasoline vehicles were higher than those in diesel vehicles. Furthermore, the emissions of 1,8-DNP from diesel vehicles cannot be disregarded. 1,8-DNP was the main gas-phase NPAHs emitted by China VI and China V diesel vehicles, accounting for 49.3 % and 26.0 %, respectively. Moreover, gas-phase PACs contributed more to the EFs than particle-phase PACs, whereas particle-phase PACs have greater toxic effects. Although the EFs of PAHs are more than 100 times those of NPAHs, the toxic equivalent concentrations (TEQBaP) of PAHs in diesel and gasoline vehicles were approximately 6.5 times and 35 times those of NPAHs. The spatial distribution characteristics revealed that PACs emissions were mainly concentrated in urban areas and highways, and the differences in the toxicity of PACs emissions between different cities depended on the proportion of diesel vehicles. The average TEQBaP of PAHs and NPAHs in Haidong, Haibei, Huangnan, Hainan, Guoluo, and Yushu was 8.42 μg/m3 and 0.36 μg/m3, respectively, while those of Xining and Haixi were 0.24-0.29 μg/m3 and 0.09-0.108 μg/m3 higher, respectively. This study provides a comprehensive understanding of the emission characteristics, health risks, and spatial distribution of PACs from diesel and gasoline vehicle PACs in urban areas.

Vascular endothelial dysfunction induced by 3-bromofluoranthene via MAPK-mediated-NFκB pro-inflammatory pathway and intracellular ROS generation

3-Bromofluoranthene (3-BrFlu) is the secondary metabolite of fluoranthene, which is classified as a polycyclic aromatic hydrocarbon, through bromination and exists in the fine particulate matter of air pollutants. Endothelial dysfunction plays a critical role in the pathogenesis of cardiovascular and vascular diseases. Little is known about the molecular mechanism of 3-BrFlu on endothelial dysfunction in vivo and in vitro assay. In the present study, 3-BrFlu included concentration-dependent changes in ectopic angiogenesis of the sub-intestinal vein and dilation of the dorsal aorta in zebrafish. Disruption of vascular endothelial integrity and up-regulation of vascular endothelial permeability were also induced by 3-BrFlu in a concentration-dependent manner through pro-inflammatory responses in vascular endothelial cells, namely, SVEC4-10 cells. Generation of pro-inflammatory mediator PGE2 was induced by 3-BrFlu through COX2 expression. Expression of COX2 and generation of pro-inflammatory cytokines, including TNFα and IL-6, were induced by 3-BrFlu through phosphorylation of NF-κB p65, which was mediated by phosphorylation of MAPK, including p38 MAPK, ERK and JNK. Furthermore, generation of intracellular ROS was induced by 3-BrFlu, which is associated with the down-regulated activities of the antioxidant enzyme (AOE), including SOD and catalase. We also found that 3-BrFlu up-regulated expression of the AOE and HO-1 induced by 3-BrFlu through Nrf-2 expression. However, the 3-BrFlu-induced upregulation of AOE and HO-1 expression could not be revised the responses of vascular endothelial dysfunction. In conclusion, 3-BrFlu is a hazardous substance that results in vascular endothelial dysfunction through the MAPK-mediated-NFκB pro-inflammatory pathway and intracellular ROS generation.

Particulate matter emissions from light-duty gasoline vehicles under different ambient temperatures: Physical properties and chemical compositions

Fine particulate matter (PM2.5) from vehicle exhaust is typically emitted at breathing height and thus imposes severe adverse effects on human health and air quality. However, there is currently limited knowledge on the characteristics of PM2.5 in exhaust, specifically its chemical components, at different ambient temperatures. Particulate emissions from typical light-duty gasoline vehicles (LDGVs) were investigated on a chassis dynamometer according to the Worldwide Harmonized Light-Duty Test Cycle at ambient temperatures of 38 °C, 28 °C, 15 °C, 5 °C and - 7 °C. The results showed a significant increase in particulate mass (PM) and particle number (PN) emissions with decreasing ambient temperature, particularly during cold starts below 5 °C. The particle size distributions exhibited distinct bimodal patterns, with accumulation-mode (AM) particles (60-125 nm) dominating the gasoline direct injection (GDI) distribution and nucleation-mode (NM) particles (8-12 nm) dominating the port fuel injection (PFI) distribution. AM particles were more temperature-sensitive than NM particles. Lower temperatures produced higher emissions of elements, carbonaceous components, and large-ring polycyclic aromatic hydrocarbons, while water-soluble ions showed an opposite trend. The total toxic equivalent, primarily influenced by benzo[a]pyrene, was significantly higher at -7 °C. The penalty distribution of LDGV PM and PN, defined by comparing the emissions at the various temperatures to those at regulated temperatures (23-30 °C), exhibited notable temporal heterogeneity (winter > autumn > spring > summer) and spatial heterogeneity (northern China > southern China). These findings are essential for establishing more stringent vehicle emission standards and improving emission models in cold environments.

Influence of oil extraction on concentration distributions, migration, secondary formation and carcinogenic risk of NPAHs and OPAHs in air and soil in an oilfield development area in China

Oil extraction leads to environmental pollution from the oilfields and dweller activities, however, knowledge of the concentration distributions, migration, secondary formation and toxicity of nitrated/oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) in oilfield regions is limited. In this research, atmospheric and soil samples in 7 different location types in an important oil industrial base in China were gathered. The ΣNPAHs and ΣOPAHs in the air ranged from 0.05 to 2.47 ng/m3 and 0.14-22.72 ng/m3, respectively, and in soil ranged from 0.22 to 17.81 ng/g and 9.69-66.86 ng/g, respectively. Both NPAHs and OPAHs in the atmosphere exhibited higher concentrations during winter. The atmospheric NPAH concentrations decreased exponentially with distance from urban area especially in the summer, revealing the impact of vehicles on the air in the Yellow River Delta area. High NPAH and OPAH concentrations were found only in soil near oil extraction facilities, indicating that the impact of oil extraction is limited to the soil near the extraction facilities. The air-soil exchanges of N/OPAHs were assessed through fugacity fraction analysis, and NPAHs were in the equilibrium-deposition state and OPAHs were in the net-deposition state in the winter. Higher incremental lifetime cancer risk (ILCR) occurred at the urban, industrial, and oilfield sites in the atmospheric samples, and the soil samples had the largest ILCR values in the oilfield sites. However, ILCR values for both air and soil did not exceed the threshold of 10-6.

Occurrence of traffic related trace elements and organic micropollutants in tunnel wash water

Substantially polluted tunnel wash water (TWW) is produced during road tunnel maintenance. Previous literature has reported the presence of trace elements and polycyclic aromatic hydrocarbons (PAHs). However, it was hypothesized that other organic pollutants are present, and more knowledge is needed to prevent environmental harm. This study reveals for the first time the presence of four short- and 17 long-chained per- and polyfluoroalkyl substances (PFASs), three benzothiazoles (BTHs), six benzotriazoles (BTRs), four bisphenols, and four benzophenones in TWW from a Norwegian road tunnel over a period of three years. Concentrations of PAHs, PFASs, BTHs, and BTRs were higher than previously reported in e.g., road runoff and municipal wastewater. Trace elements and PAHs were largely particulate matter associated, while PFASs, BTHs, BTRs, bisphenols, and benzophenones were predominantly dissolved. 26 of the determined contaminants were classified as persistent, mobile, and toxic (PMT) and are of special concern. It was recommended that regulations for TWW quality should be expanded to include PMT contaminants (such as PFPeA, PFBS, BTR, and 4-OH-BzP) and markers of pollution (like 2-M-BTH, 2-OH-BTH, and 2-S-BTH from tire wear particles). These findings highlight the need to treat TWW before discharge into the environment, addressing both, particulate matter associated and dissolved contaminants.

Enhancement of combustion effect leading to improved performance and exhaust emissions of an SI engine with ferrous oxide and graphite nanoparticles

The present study was conducted to investigate the effectiveness of new, less toxic, less harmful, and nonmetallic graphite (G) and metallic iron oxide (Fe2O3) nanofuel additives by analyzing experimentally their consequences on exhaust emissions and performance of an air cooled, single cylinder, 4-stroke gasoline engine. Fe2O3 and graphite nanoparticles at 40, 80, and 120 mg/l of gasoline concentrations were mixed with gasoline by means of a magnetic stirrer. Brake power (BP), brake-specific fuel consumption (BSFC), torque (T), brake thermal efficiency (BTE), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and carbon dioxide (CO2) emissions were the investigated parameters. Experimental results indicated that G-blends showed a higher rise in brake power, brake thermal efficiency and torque and a greater reduction in the brake-specific fuel consumption as compared to that of Fe2O3 fuel blends. Moreover, the G-blends produced less NOx and CO2 than Fe2O3 blends but produced more emissions of CO and HC than that of Fe2O3 blends. On average, G-blends produced 0.46%, 0.71%, and 1.71% more torque, power, and BTE and 2.43%, 1.87%, and 13.39% less brake-specific fuel consumption (BSFC), NOx, and CO2 than Fe2O3 blends, respectively. So, in terms of the eight parameters, four performance parameters (i.e., T, BP, BSFC, BTE), and four engine emission exhaust indicators (i.e., CO, NOx, HC, CO2), graphite nanoparticles showed more positive results for 6 parameters (T, BP, BSFC, BTE, NOx, CO2), while two parameters HC and CO showed negative results with graphite as compared to that of Fe2O3 nanoparticles. So, overall, we conclude that nanoparticles of graphite are more engine and environment friendly than that of iron oxide fuel additives.

Emission profiles, source identifications, and health risk of polycyclic aromatic hydrocarbons (PAHs) in a road tunnel located in Xi'an, China

Understanding the sources and characteristics of PM2.5-bound PAHs from traffic-related pollution can provide valuable data for mitigating air contamination from traffic in local urban regions. However, little information on PAHs is available regarding the typical arterial highway-Qinling Mountains No.1 tunnel in Xi'an. We estimated the profiles, sources, and emission factors of PM2.5-bound PAHs in this tunnel. The total PAH concentrations were 22.78 ng·m-3 and 52.80 ng·m-3 at the tunnel middle and exit, which were 1.09 and 3.84 times higher than that at the tunnel entrance. Pyr, Flt, Phe, Chr, BaP, and BbF were the dominant PAH species (representing approximately 78.01% of total PAHs). The four rings PAHs were dominant (58%) among the total PAH concentrations in PM2.5. The results demonstrated that diesel and gasoline vehicles exhaust emissions contributed 56.81% and 22.60% to the PAHs, respectively, while the corresponding value for together brakes, tyre wear, and road dust was 20.59%. The emission factors of total PAHs were 29.35 μg·veh-1·km-1, and emission factors of 4 rings PAHs were significantly higher than those of the other PAHs. The sum of ILCR was estimated to be 1.41×10-4, which accorded with acceptable level of cancer risk (10-6-10-4), PAHs should not ignored as they still affect the public health of inhabitants. This study shed light on PAH profiles and traffic-related sources in the tunnel, thereby facilitating the assessment of control measures targeting PAHs in local areas.

Emission characteristics, environmental impact assessment and priority control strategies derived from VOCs speciation sourcely through measurement for wooden furniture-manufacturing industry in China

Volatile organic compounds (VOCs) from wooden furniture-manufacturing industry is an important emission source. The VOC content levels, source profiles, emission factors and inventories, O₃ and SOA formation, and priority control strategies were investigated from the source. One hundred sixty-eight representative woodenware coatings were sampled, and VOC species and contents were determined. The VOC, O₃ and SOA emission factors per gram of coatings for three types of woodenware coatings were quantified. The total VOC, O₃ and SOA emissions from wooden furniture-manufacturing industry in 2019 were 976,976 t/a, 2,840,282 t/a, 24,970 t/a, and solvent-based coatings accounted for 98.53 %, 99.17 % and 99.6 % of the total VOC, O₃ and SOA emissions, respectively. Aromatics and esters were major organic groups, contributing 49.80 % and 36.03 % to total VOC emissions, respectively. Aromatics contributed 86.14 % and 100 % to total O₃ and SOA emissions, respectively. The top 10 species contributing to VOC, O₃ and SOA had been identified. Four benzene series, including o-Xylene, m-Xylene, toluene and ethylbenzene, were ranked as the first-class priority control species, accounting for 85.90 % and 99.89 % of the total O₃ and SOA, respectively. Priority should be given to solvent-based coatings, aromatics and four benzene series for future O₃ and SOA reduction for wooden furniture-manufacturing industry.

An evaluation of the impact of traffic on the distribution of PAHs and oxygenated PAHs in the soils and moss of the southeast Tibetan Plateau

Contaminants in high-altitude mountains such as the Tibetan Plateau (TP) have attracted extensive attention due to their potential impact on fragile ecosystems. Rapid development of the economy and society has promoted pollution caused by local traffic emissions in the TP. Among the pollutants emitted by traffic, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) are of particular concern due to their high toxicity. The TP provides an environment to explore the degree and range of contribution for traffic-induced PAHs and OPAHs. In this study, soils and moss were collected at different altitudes and distances from the G318 highway in the southeast TP. The total concentrations of PAHs (∑₁₆PAHs) and OPAHs (∑₆OPAHs) in soils were in the range of 3.29-119 ng/g dry weight (dw) and 0.54-9.65 ng/g dw, respectively. ∑₁₆PAH and ∑₆OPAH concentrations decreased logarithmically with increasing distance from traffic. A significantly positive correlation between ∑₁₆PAHs and altitude was found at sampling points closest to traffic. Dominant PAHs constituents in soil and moss included chrysene (CHR), benzo[g,h,i]perylene (BghiP), and benzo[b]fluoranthene (BbF); prevalent OPAH compounds were 9-fluorenone (9-FO) and 9,10-anthraquinone (ATQ). These compounds were related to characteristics of traffic emissions. The multiple diagnosis ratio and correlation analysis showed that exhaust emissions were the main source of the PAHs and OPAHs in the studied environment. PMF modeling quantification of the relative contribution of traffic emissions to PAHs in roadside soils was 45 % on average. The present study characterized the extent and range of traffic-induced PAH and OPAH emissions, providing valuable information for understanding the environmental behaviors and potential risks of traffic-related contaminants in high-altitude areas.

Pollution characteristics and health risk assessment of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons during heating season in Beijing

Polycyclic aromatic hydrocarbons (PAHs) and their nitrated derivatives (NPAHs) attract continuous attention due to their outstanding carcinogenicity and mutagenicity. In order to investigate the diurnal variations, sources, formation mechanism, and health risk assessment of them in heating season, particulate matter (PM) were collected in Beijing urban area from December 26, 2017 to January 17, 2018. PAHs and NPAHs in PM were quantitatively analyzed via gas chromatography-mass spectrometry (GC-MS) . Average daily concentrations of PAHs and NPAHs were (78 ± 54) ng/m³ and (783 ± 684) pg/m³, respectively. The concentrations of them were significantly higher at nighttime than at daytime, and NPAHs concentrations were 1-2 orders of magnitude lower than PAHs concentrations. In the heating season, the dominant species of PAHs include benzo[b]fluoranthene, fluoranthene, pyrene, and chrysene, while 9-nitroanthracene, 2+3-nitrofluoranthene, and 2-nitropyrene were dominant species for NPAHs. NPAHs were found to have a single peak during heating and to be primarily distributed in the 0.4-0.7 µm particle size. Primary emissions such as biomass burning, coal combustion, and traffic emissions were the major sources of PAHs. NPAHs were produced by the primary source of vehicle emissions and the secondary reaction triggered by OH radicals, as well as biomass burning during daytime. According to the health risk assessment, the total carcinogenic risk was higher in adults than in children. While upon oral ingestion, the carcinogenic risk in children was higher than that of adults, but the risk of adults was higher than children through skin contact and respiratory inhalation.

Emissions and light absorption of PM2.5-bound nitrated aromatic compounds from on-road vehicle fleets

Vehicle emissions are an important source of nitrated aromatic compounds (NACs) in particulate size smaller 2.5 μm (PM_2.5), which adversely affect human health and biodiversity, especially in urban areas. In this study, filter-based PM_2.5 samples were collected during October 14-19, 2019, in a busy urban tunnel (approximately 35,000 vehicles per day) in south China to identify PM_2.5-bound NACs. Among them, 2,8-dinitrodibenzothiophene, 3-nitrodibenzofuran and 2-nitrodibenzothiophene were the most abundant nitrated polycyclic aromatic hydrocarbons (NPAHs), while 2-methyl-4-nitrophenol, 2,4-dinitrophenol, 3-methyl-4-nitrophenol and 4-nitrophenol were the most abundant nitrophenols (NPs). The observed mean fleet emission factors (EFs) of NPAHs and NPs were 2.2 ± 2.1 and 7.7 ± 4.1 μg km^-1, and were 2.9 ± 2.7 and 10.2 ± 5.4 μg km^-1 if excluding electric and liquefied petroleum gas vehicles, respectively. Regression analysis revealed that diesel vehicles (DVs) had NPAH-EFs (55.3 ± 5.3 μg km^-1) approximately 180 times higher than gasoline vehicles (GVs) (0.3 ± 0.2 μg km^-1), and NP-EFs (120.6 ± 25.8 μg km^-1) approximately 30 times higher than GVs (4.1 ± 0.2 μg km^-1), and thus 89% NPAH emissions and 56% NP emissions from the onroad fleets were contributed by DVs although DVs only accounted for 3.3% in the fleets. Methanol solution-based light absorption measurements demonstrated that the mean incremental light absorption for methanol-soluble brown carbon at 365 nm was 6.8 ± 2.2 Mm^-1, of which the 44 detected NACs only contributed about 1%. The mean EF of the 7 toxic NACs was approximately 3% that of the 16 priority PAHs; However, their benzo(a)pyrene toxic equivalence quotients (TEQ_BaP) could reach over 25% that of the PAHs. Moreover, 6-nitrochrysene mainly from DVs contributed 93% of the total TEQ_BaP of the NACs. This study demonstrated that enhancing DV emission control in urban areas could benefit the reduction of exposure to air toxins such as 6-nitrochrysene.

Sixteen priority polycyclic aromatic hydrocarbons in roadside soils at traffic light intersections (Bratislava, Slovakia): concentrations, sources and influencing factors

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils (n = 132 at two soil depths of 0-10 cm and 10-20 cm) taken at intersections (n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑₁₆PAH) ranging from 188 to 21,950 μg/kg with a mean and median of 3021 μg/kg and 1930 μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) (r_Spearman = 0.518; p < 0.001). Statistically significant positive correlations between ∑₁₆PAH concentrations and traffic volume/road age were found in this study (r_Spearman = 0.689/0.619; p < 0.001), while ∑₁₆PAH concentration decreased with increasing distance from the road edge and was statistically lower at a soil depth of 10-20 cm than at 0-10 cm (p < 0.05). Multivariate statistical methods (principal component analysis and cluster analysis) applied to log-ratio transformed data (clr) to decrease the constant sum constraint coupled with positive matrix factorisation (PMF) modelling pointed to the dominance of pyrogenic emission sources, with 62.1% traffic-related (petrol and diesel emissions, liquid fuel and motor oil spills, and tyre wear) according to PMF results.

Characteristics and health risks of parent, alkylated, and oxygenated PAHs and their contributions to reactive oxygen species from PM2.5 vehicular emissions in the longest tunnel in downtown Xi'an, China

A vehicular emission study was conducted in the longest inner-city tunnel in Xi'an, northwestern China in four time periods (I: 07:30-10:30, II: 11:00-14:00, III: 16:30-19:30, and IV: 20:00-23:00 LST). A sum of 40 PAHs, including parent (p-PAHs), alkylated (a-PAHs), and oxygenated (o-PAHs) in fine particulate matter (PM_2.5) were quantified. The relationships between the PAHs and the formation of reactive oxygen species (ROS) were also studied. The average total quantified PAHs concentration was 236.3 ± 48.3 ng m^-3. The p-PAHs were found to be the most dominated group, accounting for an average of 88.1% of the total quantified PAHs, followed by a-PAHs (6.1%) and o-PAHs (5.8%). On the base of the number of aromatic rings, the groups of ≤5 rings (92.5 ± 1.2%) had higher fractions than the high ones (≥6 rings, 7.5 ± 1.2%) for pPAHs. Diurnal variations of PAHs subgroups exhibited the highest levels in Period III, consistent with the largest traffic counts in evening rush hours. However, less reduction of few PAHs in the night period demonstrates that the emissions of compressed natural gas (CNG) and methanol-fueled vehicles cannot be ignored while their contribution increased. High ROS activity levels were observed in the traffic-dominated samples, implying the potential oxidative damages to humans. Additionally, diurnal variation of the ROS activity was consistent with the total quantified PAHs and toxic equivalency of benzo[a]pyrene. Good correlations (R > 0.6, p < 0.05) were seen between individual groups of PAHs (especially for 3-5 rings p-PAHs, 4 rings a-PAHs, and 2-3 rings o-PAHs) and ROS activity, supporting that the vehicular emitted PAHs possibly initiate oxidative stress. The multiple linear regression analysis further illustrated that chrysene contributed the highest (25.0%) to ROS activity. In addition to highlighting the potential hazards to the PAHs from the vehicular emission, their roles to mitigate the health effects by formations of ROS were firstly reported in northwestern China.

Polycyclic aromatic hydrocarbons and their oxygenated derivatives in urban aerosol: levels, chemical profiles, and contribution to PM2.5 oxidative potential

The concentrations of polycyclic aromatic hydrocarbons (PAHs) and quinones, a subgroup of oxygenated PAHs (oxy-PAHs), were measured in PM_2.5 samples collected during warm (May-June 2019) and cold (February-March 2020) seasons in the city of Bologna, Italy. Total PAHs concentration was nearly double in winter (6.58 ± 1.03 ng m^-3) compared with spring (3.16 ± 0.53 ng m^-3), following the trend of the PM_2.5 mass concentration. Molecular diagnostic ratios suggested that, together with traffic, biomass burning was the dominant emission source contributing to the peaks of concentration of PM_2.5 registered in the cold season. Quinone level was constant in both seasons, being 1.44 ± 0.24 ng m^-3, that may be related to the increased secondary formation during warm season, as confirmed by the higher Σoxy-PAHs/ΣPAHs ratio in spring than in winter. The oxidative potential (OP) of the PM_2.5 samples was assessed using acellular dithiothreitol (DTT) and ascorbic acid (AA) assays. The obtained responses showed a strong seasonality, with higher volume-normalized (OP_V) values in winter than in spring, i.e., OP_V^DTT: 0.32 ± 0.15 nmol min^-1 m^-3 vs. 0.08 ± 0.03 nmol min^-1 m^-3 and OP_V^AA: 0.72 ± 0.36 nmol min^-1 m^-3 vs. 0.28 ± 0.21 nmol min^-1 m^-3. Both OP_V^DTT and OP_V^AA responses were significantly associated with total PAHs, as a general descriptor of redox-active PAH derivatives, associated with co-emission from burning sources or secondary atmospheric oxidation of parent PAHs. Otherwise, only winter OP_V^DTT responses showed a significant correlation with total Ʃoxy-PAHs concentration.

Recent advances in the chemical oxidation of gaseous volatile organic compounds (VOCs) in liquid phase

The chemical oxidation of gaseous volatile organic compounds (VOCs) in liquid phase may possess great advantages in its high removal efficiency, mild conditions, good reliability, wide applicability, and little potential secondary pollution, which has aroused extensive research interests in the past decade. This Overview Article summarizes the latest achievements to eliminate VOCs by chemical oxidation in liquid phase including gas-liquid mass transfer, homogeneous/heterogeneous oxidation, electrochemical oxidation, and coupling technologies. Important research contributions are highlighted in terms of mass transfer, catalytic materials, removal/mineralization efficiency, and reaction mechanism to evaluate their potential industrial applications. The current challenges and future strategies are discussed from the viewpoint of the deep degradation of refractory VOC substrates and their intermediates. It is anticipated that this review will attract more attention toward the development and application of chemical oxidation methods to clear complex industrial organic exhaust gas.

N-acetylcysteine alleviates pulmonary inflammatory response during benzo[a]pyrene-evoked acute lung injury

Benzo[a]pyrene (BaP), a representative polycyclic aromatic hydrocarbon, exists widely in automobile emissions and polluted atmosphere. The current study aimed to describe pulmonary inflammation during BaP-induced acute lung injury (ALI). All mice except controls were intratracheally instilled with a single dose of BaP (90 μg per mouse). The alveolar structure was damaged, accompanied by numerous inflammatory cell infiltration around pulmonary interstitium and small airway. Airway wall area and mean linear intercept were reduced in BaP-exposed mouse lungs. By contrast, airway wall thickness and destructive index were elevated in BaP-exposed mouse lungs. Several inflammatory genes, such as Tnf-α, Il-1β, Il-6, Mip-2, Kc, and Mcp-1, were upregulated in mouse lungs. Phosphorylated IκBα was elevated in BaP-exposed mouse lungs. Nuclear translocation of NF-κB p65 and p50 was accordingly observed in BaP-exposed mouse lungs. Several molecules of the MAPK pathway, including JNK, ERK1/2, and p38, were activated in mouse lungs. Of interest, pretreatment with N-acetylcysteine (NAC), an antioxidant, alleviated BaP-induced ALI. Moreover, NAC attenuated BaP-induced inflammatory cell infiltration in mouse lungs and inflammatory gene upregulation in A549 cells. In addition, NAC attenuated BaP-induced NF-κB activation in A549 cells and mouse lungs. These results suggest that NAC alleviates pulmonary inflammatory response during BaP-evoked ALI.

Environmental persistent free radicals in diesel engine exhaust particles at different altitudes and engine speeds

The occurrence of environmental persistent free radicals (EPFRs) in the environment has attracted a great deal of research attention. Although the major sources of EPFRs in the environment is diesel engine exhaust, the study on the emission characteristics of EPFRs at different working conditions is still very limited. An integrated engine system was adopted to simulate different working conditions of various altitudes and engine speeds, and to examine the emission process of a diesel engine. The results suggested that low engine speed and high altitude are generally associated with high PM₁₀ emission with more stable and ordered structures. Based on the analysis of PAHs on solid and gas phases, PM₁₀ generated from diesel engine at altitude higher than 2000 m may contain substantial amounts of PAHs embedded inside particles, but not adsorbed on the surface. EPFRs signal up to 1.66 × 10²⁰ spins/g were detected in PM₁₀ of the diesel exhaust. Higher engine speed and lower altitude were associated with stronger EPR signals on PM₁₀. However, the accumulated EPR signal intensities after consuming 1 L of diesel were higher at lower engine speed and higher altitude, suggesting higher overall risks. A positive correlation between R value (signal strength ratio of D and G peaks on the Raman spectra) and EPFRs intensity indicated that the EPR signals were associated with the defects of carbon structure. EPFRs intensity in particles showed no significant change in dark, and over 70% of the EPR signals survived under UV light in a one-month aging simulation. The strong persistence of these EPFRs suggested their potential long lasting and widespread risks, which should be investigated extensively.

Occurrence and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in dust of an emerging industrial city in Iran: implications for human health

Polycyclic aromatic hydrocarbons (PAHs) bounded to street dust are a severe environmental and human health danger. This study provides preliminary information on the abundance of PAHs in street dust from Rafsanjan city, Iran, where industrial emissions are high and data are lacking. Seventy street dust samples were collected from streets with different traffic loads. The United States Environmental Protection Agency (USEPA) Standard Methods 8270D and 3550C were used for the measurement of PAHs using GC mass spectroscopy. The total concentration of PAHs was 1443 ng g-1, with a range of 1380-1550 ng g-1. Additionally, the concentration of carcinogenic PAHs (∑carcPAHs) ranged from 729.5 to 889.4 ng g-1, with a mean value of 798.1 ng g-1. Pyrene was the most abundant PAH, with an average concentration of 257 ng g-1. Source identification analyses showed that vehicle emissions along with incomplete combustion and petroleum were the main sources of PAHs. The ecological risk status of the studied area was moderate. Spatial distribution mapping revealed that the streets around the city center and oil company had higher PAH levels than the other sectors of Rafsanjan. The results indicated that dermal contact and ingestion of contaminated particles were the most important pathways compared to inhalation. The mean incremental lifetime cancer risk (ILCR) was 1.4 × 10-3 and 1.3 × 10-3 for children and adults, respectively. This implies potentially adverse health effects in exposed individuals. The mutagenic risk for both subpopulations was approximately 18 times greater than the one recommended by USEPA. Our findings suggest that children are subjected to a higher carcinogenic and mutagenic risk of PAHs, especially dibenzo[a,h]anthracene (DahA), bounded to street dust of Rafsanjan. Our study highlights the need for the development of emission monitoring and control scenarios.

Environment and food safety: a novel integrative review

Environment protection and food safety are two critical issues in the world. In this review, a novel approach which integrates statistical study and subjective discussion was adopted to review recent advances on environment and food safety. Firstly, a scientometric-based statistical study was conducted based on 4904 publications collected from the Web of Science Core Collection database. It was found that the research on environment and food safety was growing steadily from 2001 to 2020. Interestingly, the statistical analysis of most-cited papers, titles, abstracts, keywords, and research areas revealed that the research on environment and food safety was diverse and multidisciplinary. In addition to the scientometric study, strategies to protect environment and ensure food safety were critically discussed, followed by a discussion on the emerging research topics, including emerging contaminates (e.g., microplastics), rapid detection of contaminants (e.g., biosensors), and environment friendly food packaging materials (e.g., biodegradable polymers). Finally, current challenges and future research directions were proposed.

Characterization of unsubstituted and methylated polycyclic aromatic hydrocarbons in settled dust: Combination of instrumental analysis and in vitro reporter gene assays and implications for cancer risk assessment

Concentrations of 34 unsubstituted and methylated polycyclic aromatic hydrocarbons (PAHs and Me-PAHs) and AhR-mediated activities in settled dust samples were determined by a combination of gas chromatography-mass spectrometry and an in vitro reporter gene assay (PAH-CALUX). The levels of Σ34PAHs and bioassay-derived benzo[a]pyrene equivalents (CALUX BaP-EQs) were significantly higher in workplace dust from informal end-of-life vehicle dismantling workshops than in common house dust and road dust. In all the samples, the theoretical BaP-EQs of PAHs (calculated using PAH-CALUX relative potencies) accounted for 28 ± 19% of the CALUX BaP-EQs, suggesting significant contribution of aryl hydrocarbon receptor (AhR) agonists and/or mixture effects. Interestingly, the bioassay-derived BaP-EQs in these samples were significantly correlated with not only unsubstituted PAHs with known carcinogenic potencies but also many Me-PAHs, which should be included in future monitoring and toxicity tests. The bioassay responses of many sample extracts were substantially reduced but not suppressed with sulfuric acid treatment, indicating contribution of persistent AhR agonists. Cancer risk assessment based on the CALUX BaP-EQs has revealed unacceptable level of risk in many cases. The application of bioassay-derived BaP-EQs may reduce underestimation in environmental management and risk evaluation regarding PAHs and their derivatives (notably Me-PAHs), suggesting a consideration of using in vitro toxic activity instead of conventional chemical-specific approach in such assessment practices.

Volatile organic compounds from a mixed fleet with numerous E10-fuelled vehicles in a tunnel study in China: Emission characteristics, ozone formation and secondary organic aerosol formation

The Chinese government has developed an ambitious project to promote the application of ethanol gasoline (E10) on a national scale since 2017. Given the difference in fuel properties between E10 and traditional gasoline, it is necessary to evaluate the volatile organic compound (VOC) emissions from E10-fuelled vehicles. In this study, a two-week sampling campaign was conducted in an urban tunnel, in which E10-fuelled vehicles were dominant, to evaluate the characteristics of VOC emissions from the mixed fleet. In total, 105 VOC species were identified, and the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) were estimated. The results showed that for vehicular VOC concentrations in the tunnel, alkanes, oxygenated VOCs (OVOCs) and alkenes were the most abundant VOC groups, with the average proportion being more than 80% of the total VOCs. The fleet-average VOC emission factor (EF) was 14.8 mg/km/veh, which was much lower than that from traditional gasoline-fuelled vehicle fleets, and alkanes, OVOCs, alkenes and aromatics were the major VOC groups. Because of the large number of E10-fuelled vehicles in the mixed fleet, a high proportion of OVOCs among the vehicular VOC emissions was observed. Ethane, acrolein, ethanol, ethylene and toluene were the top five VOC species with the largest EF in VOC emissions from the fleet. Alkenes were the main contributors with an average contribution of 43.9% of the total OFP, whereas aromatics dominated the total SOAFP by 95.8% on average. These results may provide a reference for the extensive application of ethanol gasoline and the development of vehicular emission models.

Environmental and health risks of VOCs in the longest inner-city tunnel in Xi'an, Northwest China: Implication of impact from new energy vehicles

Traffic source-dominated volatile organic compound (VOC) samples were collected during four time-intervals in a day (Ⅰ: 7:30-10:30, Ⅱ: 11:00-14:00, Ⅲ: 16:30-19:30, and Ⅳ: 20:00-23:00) in a tunnel in summer, 2019, in Xi'an, China. The total measured VOC (TVOC) in periods Ⅰ and Ⅲ (rush hours, 107.2 ± 8.2 parts per billion by volume [ppbv]) was 1.8 times that in periods Ⅱ and Ⅳ (non-rush hours, 58.6 ± 13.8 ppbv), consistent with the variation in vehicle numbers in the tunnel. The considerably elevated ethane and ethylbenzene levels could have been attributed to emissions from compressed natural gas vehicles and the rapid development of methanol-fueled taxis in Xi'an in 2019. The mixing ratios of benzene, toluene, ethylbenzene, and xylenes (BTEX) contributed 9.4%-12.7% to TVOCs, and the contributions were nearly 40% higher in periods Ⅰ and Ⅲ than in Ⅱ and Ⅳ, indicating that BTEX levels were strongly affected by vehicle emissions. The indicators of motor vehicle emission, namely ethylene, propylene, toluene, m/p-xylenes, o-xylene, and propane, contributed to more than half of the ozone formation potential in this study. The noncarcinogenic risks of VOCs in this study were within the international safety standard, whereas the carcinogenic risks exceeded the standard by 2.3-4.6 times, suggesting that carcinogenic risks were more serious than noncarcinogenic risks. VOCs presented 2.2 and 1.4 times noncarcinogenic and carcinogenic risks during rush hours than during non-rush hours, respectively. Notably, the carcinogenic risk in period Ⅳ was comparable with that in period Ⅲ; however, the vehicle numbers and VOC mixing ratios were the lowest at night, which may have attributed to the increasing number and proportion of methanol M100-fueled vehicles in the tunnel. Therefore, VOCs emitted by new energy vehicles should also be seriously considered while evaluating fossil fuel vehicle emissions.

Atmospheric polycyclic aromatic hydrocarbons (PAHs) at urban settings in Pakistan: Spatial variations, sources and health risks

For the first time, this study presents gaseous and particulate-bound (PM_2.5) polycyclic aromatic hydrocarbons (PAHs) in ambient air samples collected from eight major cities of Pakistan. Diurnal air samples (gaseous and PM_2.5) were collected in summer 2014 on polyurethane foam and quartz fiber filters using high volume-active air sampler. The US-EPA enlisted 16 priority PAHs in particulate and gaseous phase were measured on gas chromatograph equipped with mass spectrometer detector. The total PAHs concentrations ranged between 188 pg m^-3 (in Gilgit), and 2340 pg m^-3 (in Lahore). The decreasing order of PAHs concentrations in various cities was in the following order: Lahore > Rawalpindi > Multan > Faisalabad > Karachgi > Peshawar > Quetta > Gilgit. Phenanthrene showed the highest concentration, accounted 18% of total PAHs followed by fluoranthene (12% of total PAHs). This study showed that the gaseous fractions were predominant in the ambient air. Source apportionment analysis revealed that biomass combustion, vehicular emissions and diesel combustion in power generators were the potential PAHs emissions sources. The lifetime lungs cancer risk (LLCR) was in the range of 8.28 × 10^-7 to 2.09 × 10^-5 depicting mild cancer risk to the residents on exposure to atmospheric PAHs. Therefore, it is recommended to monitor atmospheric PAHs throughout the year and also adopt environmentally friendly fuels to reduce PAHs pollution and health risks in the country.

On-Road Emission Characteristics of Volatile Organic Compounds from Light-Duty Diesel Trucks Meeting Different Emission Standards : Investigation on the characteristics of tailpipe volatile organic compound emissions with a portable emissions measurement system

On-road tailpipe volatile organic compounds (VOCs) were sampled from light-duty diesel trucks (LDDTs) compliant with Euro III to V, and a total of 102 VOC species were quantified. The composition characteristics and carbon number distributions were investigated, and the contribution of individual VOC to ozone formation potentials (OFPs) was weighted. Results showed that alkanes were the major VOC species, accounting for approximately 65.5%. VOC emissions decreased significantly as the standards became stricter, especially for alkanes and aromatics; and the VOC emissions on highway were much lower than those on urban roads. Carbon number distribution of VOCs was mainly concentrated in C3‐C4 and C10‐C12. Aromatics were the major contributors to ozone formation, taking up 49.3‐57.6% of the total OFPs, and naphthalene, 1-butene, dodecane, 1,2,3-trimethylbenzene and 2-propenal were the top five species. The information provided insight into the tailpipe VOC emission characteristics and may help decision makers drafting related emission policies.

Polycyclic aromatic hydrocarbon contamination along roads based on levels on vehicle window films

Vehicular emissions are known to be major contributors of airborne polycyclic aromatic hydrocarbons (PAHs) in cities. In order to assess the long-term contamination of PAHs along roads, we collected organic films from vehicle windows (26 private cars and 4 buses, in Shanghai, China) and used mathematical models to convert the film-bound PAH concentrations to the airborne PAH concentrations. The field measurements of airborne PAHs revealed that the partitioning and Level III fugacity model was suitable to estimate the airborne concentrations of high and low volatile PAHs (expect for naphthalene), respectively. The total airborne PAH concentrations along roads in Shanghai ranged from 0.83 to 3.37 μg m^-3 and the incremental lifetime cancer risks (ILCR_total) by exposure to PAHs along roads were greater than the USEPA lower guideline of 10^-6, indicating non-negligible carcinogenic risks to drivers and passengers, especially via ingestion processes. This study provided a practicable method to investigate long-term air contamination of PAHs in vehicles and along roads based on film-bound PAH on vehicle windows. In addition, it was also possible to investigate the health risk in vehicles as a result of exposure to PAHs. Comparisons of PAHs between roads and shipping lanes also facilitated the delineation of vehicular and shipping PAH inventories. A capsule that summarizes the main finding of the work: Investigating film-bound PAH on vehicle windows is a practicable pathway to investigate the long-term contamination of PAHs in vehicles and along roads. This method can not only simplify the sampling processes, but the model calculations. The results also enabled investigations into ILCR in vehicles and specified source apportionment of traffic PAHs.

Polycyclic and nitro-polycyclic aromatic hydrocarbon pollution characteristics and carcinogenic risk assessment of indoor kitchen air during cooking periods in rural households in North China

Medium-flow atmospheric samplers were used to collect particulate (PM_2.5) and gaseous samples from the indoor kitchen of each of 35 randomly selected rural houses in North China while a meal was being cooked. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 9 nitro-PAHs (NPAHs) in the samples were quantified by high-performance liquid chromatography (HPLC). This study provided the real PAH and NPAH pollution characteristics and carcinogenic risk produced by cooking in rural indoor kitchens in North China. The mean PAH and NPAH concentrations in air in the indoor kitchens during cooking periods were 4049.1 and 1741.6 ng/m³, respectively. The PAH and NPAH concentrations were lower in the particulate phase than the gaseous phase. The mean PAH and NPAH concentrations were much higher for cooking using coal than for cooking using liquefied petroleum gas (LPG) or electricity. The PAH and NPAH benzo[a]pyrene toxic equivalent (TEQ_BaP) concentrations for cooking using coal were 1823.3 and 2760.9 ng/m³, respectively. Lower PAH and NPAH concentrations were found in kitchens with than without range hoods. Range hoods decreased the PAH and NPAH TEQ_BaP concentrations by 68.8% and 61.9%, respectively. Appropriate fuel and ventilation choice will improve air pollution in indoor kitchens during cooking. The results provide important evidence for changing cooking habits and developing policies for cooking in rural China.

PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) and nitrated-PAHs (NPAHs) emitted by gasoline vehicles: Characterization and health risk assessment

Seventeen polycyclic aromatic hydrocarbons (PAHs) and eight nitrated PAHs (NPAHs) in PM_2.5 and conventional gaseous pollutants exhausted from 54 in-use gasoline vehicles encompassing different emission standards (China 1 to China 5) were tested on the chassis and engine dynamometric test bench. With the increase of emission standards, a decrease in the emissions of PM_2.5-bound PAHs and NPAHs was detected. The emission factors (EFs) of total PAHs and NPAHs in PM_2.5 emitted by the vehicles with a mileage of >100,000 km were greater than that emitted by the vehicles with driving mileage of <100,000 km under all the five emission standards. The EFs of PM_2.5-bound PAHs and NPAHs emitted from port fuel injection engines were larger than that from gasoline direct injection engines. The emissions of PM_2.5-bound PAHs and NPAHs were less correlated with the exhaust of CO, while the hydrocarbon (HC) emissions were strongly correlated with the PM_2.5-bound PAHs emissions. The emissions of NPAHs and NOx had an inverse correlation. The toxic (TEQs) of total PAHs and NPAHs in China 3, China 4 and China 5 were significantly reduced compared to China 1 and China 2, which may be related to exhaust technology improvements. Although the EFs of NPAHs were significantly lower than those of PAHs, the TEQs of NPAHs were higher, which indicates that the toxic effect of NPAHs emitted by gasoline vehicles were stronger than PAHs.

Evaluation of water quality in the South-to-North Water Diversion Project of China using the water quality index (WQI) method

The world's longest trans-basin water diversion project, the Middle-Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC), has officially been in operation for over 5 years since December 2014. Its water quality status has always attracted special attention because it is related to the health and safety of more than 58 million people and the integrity of an ecosystem covering more than 155,000 km². This study presented and analysed the spatio-temporal variations and trends of 16 water quality parameters, including pH, water temperature (WT), dissolved oxygen (DO), permanganate index (PI), five-day biochemical oxygen demand (BOD₅), fecal coliform (F. coli), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃^-N), sulphate (SO₄^2-), fluoride (F^-), mercury (Hg), arsenic (As), selenium (Se), copper (Cu), and zinc (Zn), which were determined monthly from samples collected at 27 water quality monitoring stations in the MR of the SNWDPC from March 2016 to February 2019. The water quality index (WQI) was used to evaluate the seasonal and spatial water quality changes during the monitoring period, and a new WQI_min model consisting of five crucial parameters, i.e., TP, F. coli, Hg, WT, and DO, was built by using stepwise multiple linear regression analysis. The results demonstrated that the water quality status of the MR of the SNWDPC has been steadily maintained at an "excellent" level during the monitoring period, with an overall average WQI value of 90.39 and twelve seasonal mean WQI values ranging from 87.67 to 91.82. The proposed WQI_min model that uses the selected five key parameters and the weights of those parameters has exhibited excellent performance in the water quality assessment of the project, with the coefficient of determination (R²), Root Mean Square Error (RMSE), and Percentage Error (PE) values of 0.901, 2.21, 1.93%, respectively, showing that the proposed WQI_min model is a useful and efficient tool to evaluate and manage the water quality. For the management department, the risk sources near certain stations with abnormally high values should be carefully inspected and strictly managed to maintain excellent water quality. The potential risks of algae proliferation in this project should be of concern in future research.

Levels, spatial distribution, and source identification of airborne environmentally persistent free radicals from tree leaves

Environmentally persistent free radicals (EPFRs) are receiving increasing concern due to their toxicity and ubiquity in the environment. To avoid restrictions imposed when using a high-volume active sampler, this study uses tree leaves to act as passive samplers to investigate the spatial distribution characteristics and sources of airborne EPFRs. Tree leaf samples were collected from 120 sites in five areas around China (each approximately 4 km × 4 km). EPFR concentrations in particles (<2 μm) on the surface of 110 leaf samples were detected, ranging from 7.5 × 10¹⁶ to 4.5 × 10¹⁹ spins/g. For the 10 N.D. samples, they were all collected from areas inaccessible by vehicles. The g-values of EPFRs on 68% leaf samples were larger than 2.004, suggesting the electron localized on the oxygen atom, and they were consistent with the road dust sample (g-value: 2.0042). Significant positive correlation was found between concentrations of elemental carbon (tracer of vehicle emissions) and EPFRs. Spatial distribution mapping showed that EPFR levels in various land uses differed noticeably. Although previous work has linked atmospheric EPFRs to waste incineration, the evidence in this study suggests that vehicle emissions, especially from heavy-duty vehicles, are the main sources. While waste incinerators with low emissions or effective dust-control devices might not be an important EPFR contributor. According to our estimation, over 90% of the EPFRs deposited on tree leaves might be attributed to automotive exhaust emissions, as a synergistic effect of primary exhausts and degradation of aromatic compounds in road dust. With adding the trapping agent into the particle samples (<2 μm), signals of hydroxyl radicals were observed. This indicates that EPFRs collected from this phytosampling method can lead to the release of reactive oxygen species (ROS) once they are inhaled by human beings. Thus, this study helps highlight EPFR "hotspots" for potential health risk identification.

PAH levels in a furniture-manufacturing city atmosphere

In this study, in order to determine atmospheric PAH concentrations in Inegol/Turkey, ambient air samples were collected from two different sites representing industrial and uncontrolled furniture manufacturers regions. Sampling campaign took place between December 2017 and November 2018. Air samples were collected using high volume air samplers (HVAS) and PAH concentrations were determined in both gas and particulate phases. The mean of the atmospheric PAH concentrations obtained in the gas phase in the furniture workshops (FW) and industrial district (ID) regions were 697.82 ± 637 ng/m³ and 772.92 ± 864.23 ng/m³, respectively. The concentrations in the particulate phase in the regions were 413.52 ± 430.23 ng/m³ and 342.40 ± 527.48 ng/m³, respectively. The average total (gas + particlulate phases) concentration of ∑₁₆PAH determined in the site of FW was 1111.34 ± 1045.24 ng/m³ while that was 772.92 ± 864.23 ng/m³ in ID. These values are over the ambient levels reported for urban sites wherein big industries exist around the world. Additionally, the average of particle phase percentage was 30% because of nearby combustion sources. The determination of possible sources of PAHs in the regions was performed using principal component analysis (PCA). PCA results showed that the main sources of pollutants of the regions are intertwined (combustion, traffic, industries). However, the most effective source is thought to be uncontrolled combustion of furniture wastes as fuel for residential heating. Health risks for the citizens were calculated for both regions and were found not to be at high-class risk.

A modified receptor model for historical source apportionment of polycyclic aromatic hydrocarbons in sediment

Pollution of polycyclic aromatic hydrocarbons (PAHs) in the environment is becoming increasingly serious with the development of the economy. Source analysis is the key step in reducing PAHs pollution in the environment, and existing methods are usually based on receptor models. However, when these methods are applied to the distribution of PAHs in sediments, overestimation or underestimation often occurs. Therefore, this paper proposes an improved model based on principal component analysis and multiple linear regression. The model has been applied to study the pollution of PAHs in sediments of Taihu Lake in China over several decades. Compared with existing models, principal component analysis followed by multiple linear regression of source (PCA-MLRS) can identify specific emission sources and quantify the impact of each emission, and the source resolution accuracy of the strong toxic molecules BaP and DBA is significantly higher than that of other models. Biomass combustion source is the main material source of Phe, Ant, Flu and Pyr in Taihu Lake sediment, and their contribution rates are 85.2%, 44.8%, 58.9% and 62.2%, respectively. The coal combustion source is the main material source of the 5-ring molecule BaP and the 6-ring molecules InP and BP. The contribution rates of coal combustion to BaP, InP and BP are 70.1%, 72.9% and 72.1%, respectively, and this contribution has increased since 1985. The contribution of petroleum oil combustion source and coal combustion source to PAHs in sediments of Taihu Lake is consistent. They are the main sources of heavy molecular PAHs such as BaA, BbF, BkF and DBA, and their contributions are 56.5%, 36.8%, 43.9% and 67.3% respectively. The results are related to the different emission and management characteristics of PAHs from different sources and the different behavior characteristics of low and high molecular weight PAHs in the environment.

Characteristics of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and Nitro-Polycyclic Aromatic Hydrocarbons at A Roadside Air Pollution Monitoring Station in Kanazawa, Japan

Polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM_2.5 samples were collected at a roadside monitoring station in Kanazawa, Japan, in every season from 2017 to 2018. Nine PAHs and five NPAHs were determined using high-performance liquid chromatography with fluorescence detection and chemiluminescence detection, respectively. The mean concentrations of PAHs and NPAHs were highest in winter and lowest in summer. Fluoranthene and pyrene were the dominant PAHs and 1-nitropyrene was the dominant NPAH in all seasons, and these compounds were mainly emitted by diesel vehicles. The concentration ratio of benzo(a)pyrene (BaP) to benzo(ghi)perylene (BgPe) ((BaP)/(BgPe)) and of indeno(1,2,3-cd)pyrene (IDP) to the sum of IDP and benzo(ghi)perylene (BgPe) ((IDP)/((IDP)+(BgPe0) might still be useful indicators for identifying traffic emission sources today. Moreover, our results showed that the carcinogenic risk in all seasons was below the acceptable limit set by the WHO.

Assessment of PM2.5 and PAH content in PM2.5 emitted from mobile source gasoline-fueled vehicles in concomitant with the vehicle model and mileages

This study investigates the PM_2.5 emission and analyses the PAHs content in PM_2.5 emitted from gasoline-fueled vehicles. Outflow from the vehicles appear to be the ultimate source of PAHs in metro urban communities since the emission from gasoline vehicle increases the wellbeing hazard due to contiguity of exposure to gasoline exhaust. In this study, fifteen vehicles were randomly taken for sampling, where sixteen priority PAHs concentration were investigated. The study was performed on the vehicles with different Euro standard emission by taking into consideration the European legislative levels for vehicles on the toxic gaseous emission. Among all the PAHs outflow components of PM_2.5 radiated in the exhaust of gasoline engines, the average concentration of total PAHs discharged was 0.377ng/L-fuel, while the total BaPeq concentration was 0.00993ng/L-fuel.

Characterization and quantification of PM2.5 emissions and PAHs concentration in PM2.5 from the exhausts of diesel vehicles with various accumulated mileages

Road traffic is one of the main sources of particulate matter in the atmospheric environment. Notwithstanding its significance, there are noteworthy challenges in quantitative assessment of its contribution to the concentrations of airborne. This study reports on the characterization and quantification of PM_2.5 emissions and PAHs concentration in PM_2.5 from the exhausts of on-road diesel vehicles with various accumulated mileages in Kaohsiung City, Taiwan. Urban areas could be a subject matter not just in connection to deprived air quality, but similarly to pollution of other significant environmental media by air contaminants. To that end, our study intends to estimate the PM_2.5 emissions from diesel vehicles using diesel fuels and to analyze the PM_2.5 emissions and PAHs concentration in PM_2.5. In this study, particulate matters (PM_2.5) were characterized and quantified from a place impacted by diesel vehicles fueled with diesel in Kaohsiung City, Taiwan. The tested diesel vehicles with various accumulated mileages overs the model year comprising of the vehicles registered from 1984 to 2012 from different manufacturers (or brands) ranging from 8733 to 965,026 km (average 445,433 km) accumulative mileages. Exhaust constituents include CO, NOx, PM_2.5 and particle phase PAHs. The concentrations of twenty-one (21) priority polycyclic aromatic hydrocarbons (PAHs) were studied in the samples by their relationship with atmospheric PM_2.5. However, in relations to cumulative mileages, lower cumulative mileage (mileage <20,000 km) has the lowest CO and NOx emission factors. The mileage ranged from 20,001 to 30,000 km had an increased CO and NOx emission factors, respectively. Interestingly, with the increased high number of mileages ranged from 30,001 to 50,000 km, CO and NOx emission factor was observed to be declining, respectively. This could be attributed to the technological changes on new diesel vehicle models. But nonetheless, the trend of CO emission factor was found to be higher with an increasing of cumulative mileages as compared to the mileage that reached lower than 30,000 km.

Atmospheric levels, variations, sources and health risk of PM2.5-bound polycyclic aromatic hydrocarbons during winter over the North China Plain

PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) during winter 2015 at three urban sites, including Beijing, Tianjin and Shijiazhuang, and one background site (Xinglong) over the North China Plain (NCP) were investigated. The spatial variations of PAHs showed the same trends with PM_2.5 mass concentrations, i.e. the highest PAHs concentrations was in Shijiazhuang, followed by Tianjin, Beijing and the lowest PAHs concentrations was in Xinglong. The diurnal variations of PAHs exhibited PAHs concentrations during nighttime were higher than those during daytime. The dominant species in PAHs were fluranthene and benzo[b + k]fluoranthene, indicating that diesel vehicle emission, coal combustion and biomass burning could be important and potential sources for PAHs over the NCP. There results were supported by diagnostic ratios analysis. But coefficient of divergence analysis showed that a high extent of spatial contrast among four sampling sites, except between Beijing and Tianjin. Analysis of toxicity equivalent quantities (TEQ) and the lifetime excess cancer risk (ECR) from inhalation exposure to PAHs showed that 818, 1517, 5129 and 182 cases per 100,000 people exposed in Beijing, Tianjin, Shijiazhuang and Xinglong, respectively, which were much higher than the threshold value suggested by US-EPA, i.e. 1 case per 100,000 people, and indicating that the NCP suffered from very serious health risk from PAHs, especially in Shijiazhuang.