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Highlights • A risk-benefit analysis was performed to estimate the optimal outdoor moderate physical activity (MPA) duration under varying particulate matter (PM2.5) concentrations. • An inverse nonlinear relationship was identified between optimal MPA duration and background PM2.5 concentration levels. • The relationship between optimal MPA duration and background PM2.5 concentration levels was stronger when exercising at a location closer to a source of air pollution. • Compared to the general adult population, adults aged 60 years and older had substantially steeper curves. • The health benefit of outdoor MPA by far outweighs the health risk of PM2.5 pollution for the global average urban background concentration., Objective Outdoor physical activity (PA) brings important health benefits, but exposure to polluted air increases health risks. This study aimed to quantify the tradeoff of PA under fine particulate matter (PM2.5) air pollution by estimating the optimal PA duration under various pollution levels. Methods A risk-benefit analysis was performed to estimate the optimal outdoor moderate PA (MPA) duration under varying PM2.5 concentrations. Results An inverse nonlinear relationship was identified between optimal MPA duration and background PM2.5 concentration levels. When background PM2.5 concentration increased to 186 µg/m3, the optimal outdoor MPA duration decreased to 2.5 h/week, the minimum level recommended by current PA guidelines. When background PM2.5 concentration further increased to 235 µg/m3, the optimal outdoor MPA duration decreased to 1 h/week. The relationship between optimal MPA duration and background PM2.5 concentration levels was stronger when exercising at a location closer to a source of air pollution. Compared to the general adult population, adults aged 60 years and older had substantially steeper curves—the optimal outdoor MPA duration decreased to 2.5 h/week when background PM2.5 concentration reached 45 µg/m3. Conclusion The health benefit of outdoor MPA by far outweighs the health risk of PM2.5 pollution for the global average urban background concentration (22 μg/m3). This modeling study examined a single type of air pollutant and suffered from measurement errors and estimation uncertainties. Future research should examine other air pollutants and indoor PA, incorporate short- and mid-term health effects of MPA and air pollution into the risk-benefit analysis, and provide estimates specific for high-risk subgroups., Graphical Abstract Image, graphical abstract

Objectives. To investigate the effects of coal-fired power plant closures on zip code–level rates of emergency department visits for asthma-related conditions among 0- to 4-year-old children in Chicago, Illinois. Methods. We used data on wind, population, PM(2.5) (particulates measuring ≤ 2.5 µm in diameter), and zip code–level rates of emergency department visits for asthma-related conditions among 0- to 4-year-old children between 2009 and 2017 in Chicago. The difference-in-differences research design compared rates of emergency department visits in zip codes near 3 coal-fired power plants before and after their closures to rates in zip codes farther away during the same time period. Results. We found that emergency department visits for asthma-related conditions among 0- to 4-year-old children decreased by 12% in zip codes near the 3 coal-fired power plants following their closures relative to rates in zip codes farther away during the same period. The crude and age-specific rates of emergency department visits decreased by 2.41 visits per ten thousand inhabitants and 35.63 visits per ten thousand children aged 0 to 4 years, respectively. Conclusions. Our findings demonstrate that closing coal-fired power plants can lead to improvements in the respiratory health of young children.

Long-range atmospheric transport (LRAT) plays a crucial role in the occurrence of persistent organic pollutants (POPs) in remote regions. When studying the LRAT of POPs on the Tibetan Plateau, westerly-controlled regions have received insufficient attention compared with regions influenced by the Indian monsoon or air flow from East Asia. We investigated the residual levels of POPs in soils from the eastern Pamirs and used air backward trajectory analysis to elucidate the influence of potential source regions via LRAT. Organochlorine pesticides (OCPs, mainly comprising DDTs, HCHs, and HCB), polychlorinated biphenyls (PCBs, mainly comprising penta- and hexa-CBs), and polycyclic aromatic hydrocarbons (PAHs, mainly comprising three- and four-ring) were detected at low concentrations of 40-1000,MDL-88, and 2100-34,000 pg/g, respectively. We elucidated three major geographical distribution patterns of POPs, which were influenced by (1) the distribution of total organic carbon and black carbon in soil, (2) historical use of pesticides in the Tarim Basin, and (3) continuous emissions. Central Asia and the Tarim Basin were major potential source regions of POPs reaching the eastern Pamirs via LRAT. Historical use of technical HCH or lindane and technical DDT in potential source regions may contribute to the accumulation of HCHs and DDTs in the eastern Pamirs, respectively. Local sources seem to play a more important role in the occurrence of PAHs in the study area. By being under the control of less contaminated westerly air flow, the eastern Pamirs are more pristine than the core of the Tibetan Plateau where the Indian and East Asia monsoons deliver contaminants from highly industrialized areas in East China and India.

Carbon monoxide (CO) is primarily the result of incomplete combustion, which has important impacts on the atmospheric chemical cycle and climate. Improved quantitative characterization of long-term CO trends is important for both atmospheric modeling and the design and implementation of policies to efficiently control multiple pollutants. Due to the limitations of high time-resolution and high-quality long-term observational data, studies on long-term trends in the CO concentration in China are quite limited. In this study, the observational data of the concentration of CO in a rural site of Beijing during 2006–2018 was used to analyze the long-term trend in CO concentration in Beijing. The Theil-Sen method and the generalized additive model (GAM)-based method, were used to conduct the trend estimation analysis. We found that the concentration of CO at the Shangdianzi site showed a significant downward trend during 2006–2018, with a decline rate of 22.8 ± 5.1 ppbV per year. The declining trend in CO also showed phasic characteristics, with a fast decreasing rate during the period of 2006–2008, stable variations during the period of 2009–2013 and a continuous downward trend after 2013. The declining trend in the CO concentration in the south to west (S-W) sectors where the polluted air masses come from is more rapid than that in the sectors where the clean air masses come from. The declining trend in the CO concentration implies the improved combustion efficiency and the successful air pollution control policies in Beijing and the surrounding area.

The national lockdown policies have drastically disrupted socioeconomic activities during the COVID-19 pandemic in China, which provides a unique opportunity to investigate the air quality response to such anthropogenic disruptions. And it is meaningful to evaluate the potential health impacts of air quality changes during the lockdown, especially for PM2.5 with adverse health effects. In this study, by using PM2.5 observations from 1388 monitoring stations nationwide in China, we examine the PM2.5 variations between the COVID-19 lockdown (February and March in 2020) and the same period in 2015-2019, and find that the national average of PM2.5 decreases by 18 μg m−3, and mean PM2.5 for most sites (about 75%) decrease by 30%-60%. The anthropogenic and meteorological contributions to these PM2.5 variations are also determined by using a stepwise multiple linear regression (MLR) model combined with the Kolmogorov-Zurbenko filter. Our results show that the change of anthropogenic emissions is a leading contributor to those widespread PM2.5 reductions, and meteorological conditions have the negative influence on PM2.5 reductions for some regions, such as Beijing-Tianjin-Hebei (BTH). Additionally, the avoided premature death due to PM2.5 reduction is estimated as a predicted number based on a log-linear concentration-response function. The total avoided premature death is 9952 in China, with dominant contribution (94%) from anthropogenic emission changes. For BTH, Yangtze River Delta, Pearl River Delta and Hubei regions, the reductions of PM2.5 are 24.1, 24.3, 13.5 and 29.5 μg m−3, with the avoided premature deaths of 1066, 1963, 454 and 583, respectively., Graphical abstract Image, graphical abstract

Visibility observed at different altitudes is favorable to understand the causes of air pollution. We conducted 4-years of observations of visibility at 2.8 and 60 m and particulate matter (PM) concentrations from 2015 to 2018 in Shenyang, a provincial city in Northeast China. The results indicated that visibility increased with the increasing height in winter (especially at night), and decreased with height in summer (especially at the daytime). PM concentration exhibited opposite vertical variation to visibility, reflecting that visibility degrades with the increase of aerosol concentration in the air. The radiosonde meteorological data showed that weak turbulence in the planetary boundary layer (PBL) in winter favored aerosols’ accumulation near the surface. Whereas in summer, unstable atmospheric conditions, upper-level moister environment, and regional transport of air pollutants resulted in the deterioration of upper-level visibility. Inter-annual variation in the two-level visibility indicated that the upper-level visibility improved more significantly than low-level visibility, much likely due to the reduction in emission of elevated point sources in Shenyang. Our study suggested that strengthening the control of surface non-point emissions is a promising control strategy to improve Shenyang air quality.

This project investigated passive adsorbent sampling of light (C2-C5) hydrocarbons which are the sensitive tracers of fugitive emissions from oil and natural gas (ON under the worst case relative humidity level of 95% RH, VOCs uptake rates dropped to 27-39% of those in dry air. This effect potentially causes results to be biased low when cartridges are deployed at high RH, including overnight when RH is often elevated over daytime levels. Nonetheless, representative sampling results were obtained under ambient conditions during three field studies where cartridges were evaluated alongside whole air sample collection in canisters. Agreement varied by compound: Ethane and alkenes correlated poorly and could not be analyzed with satisfactory results; results for C3-C5 alkanes were much better: i-butane correlated with R2 > 0.5, and propane, n-butane, i-pentane, and n-pentane with R2 > 0.75, which demonstrates the feasibility of the passive sampling of these latter O&NG tracers.

The aim of the study is to present the results of mathematically modeled influence of the average speed on the pollutant released in the air during the cold-start process. There were taken into consideration the emission from the passenger cars (PCs) for the different fuel types, vehicles’ segments (including hybrid), and the Euro standard. In the article the simulations was performed using the COPERT software, as well as WLTP-based research. The modelling results there are presented show that the change in average speed has a significant effect on air pollutant (CO2, NOx, NMVOC, CO) emissions released in cold-start process. Furthermore, the results show that pollutants’ emissions are sensitive to average speed fluctuations.

Much attention is drawn to polycyclic aromatic hydrocarbons (PAHs) as an air pollutant due to their toxic, mutagenic and carcinogenic properties. Therefore, to understand the levels, seasonality, sources and potential health risk of PAHs in two distinct geographical locations at Karachi and Mardan in Pakistan, total suspended particle (TSP) samples were collected for over one year period. The average total PAH concentrations were 31.5 ± 24.4 and 199 ± 229 ng/m3 in Karachi and Mardan, respectively. The significantly lower concentration in Karachi was attributed to diffusion and dilution of the PAHs by the influence of clean air mass from the Arabian sea and high temperature, enhancing the volatilization of the particle phase PAHs to the gas phase. Conversely, the higher concentration (~6 times) in Mardan was due to large influence from local and regional emission sources. A clear seasonality was observed at both the sites, with the higher values in winter and post-monsoon due to higher emissions and less scavenging, and lower values during monsoon season due to the dilution effect. Diagnostic ratios and principal component analysis indicated that PAHs in both sites originated from traffic and mixed combustion sources (fossil fuels and biomass). The average total BaP equivalent concentrations (BaPeq) in Karachi and Mardan were 3.26 and 34 ng/m3, respectively, which were much higher than the WHO guideline of 1 ng/m3. The average estimates of incremental lifetime cancer risk from exposure to airborne BaPeq via inhalation indicated a risk to human health from atmospheric PAHs at both sites.

This study investigated concentrations of PM2.5, PM10, SO2, NO2, CO and O3, and air quality index (AQI) values across 368 cities in mainland China during 2015–2018. The study further examined relationships of air pollution status with local industrial capacities and vehicle possessions. Strong correlations were found between industrial capacities (coal, pig iron, crude steel and rolled steel) and air pollution levels. Although statistical and significant reductions of PM2.5, PM10, SO2, NO2, CO and AQI values were observed in response to various laws and regulations in industrial sectors, both particle and gaseous pollutants still had annual average concentrations above recommended limits. In order to further reduce air pollution, more efforts can be done to control traffic emissions caused by minicars and heavy trucks, which was revealed after investigating 16 vehicle types. This was also consistent with the apparent air quality improvement during the COVID-19 lockdown period in China in 2020, despite industrial operations being still active at full capacities.

Submicron aerosol is of extensive concern not only due to its significant impact on air quality but also because it is detrimental to human health. In this study, we investigated the characteristics, sources and chemical processes of submicron aerosol based on real-time online measurements of submicron aerosols (NR-PM1) during December 2015 at an urban site in Beijing. The average mass concentration of NR-PM1 was 92.5±84.9 µg/m3, the hourly maximum was 459.1 µg/m3 during the entire observation. The organic aerosol (OA) (55%) was the largest contributor to NR-PM1. The average mass concentration of PAHs was 0.217±0.247 µg/m3, exhibiting the highest concentration at night and the lowest levels in the daytime. The average mass concentration of organic nitrate was 2.52±2.36 µg/m3 and that of inorganic nitrate was 7.62±8.22 µg/m3, accounting for 36% and 64%, respectively, of the total nitrate mass. Positive matrix factorization (PMF) differentiated the OA into five chemical components including LV-OOA, SV-OOA, COA, HOA and CCOA, accounting for 22%, 16%, 13%, 25% and 24% respectively, of the total OA. The average NR-PM1 mass concentration on the heavy polluted days (HPD) was 182.8±70.2 µg/m3, which was approximately 9 times that on clean days (CD). The enhanced secondary formation of SNA was evident on HPD, especially the rapid increase of sulfate (23%) and nitrate (19%).

‘Co-control’, or synergistically reducing CO2 and local air pollutant emissions, is an important strategy for cities to achieve ‘low carbon’ and ‘blue sky’ simultaneously. However, there were few studies to evaluate and compare the level of co-control of CO2 and local air pollutants in cities yet. The present study proposed qualitative and quantitative methods to evaluate the level of co-control of CO2 and three local air pollutant (SO2, NOx, and particulate matter PM) emissions in key environmental protection cities in China over two periods (2012–2015 and 2015–2018). Statistical analysis found that, though three local air pollutant emissions positively correlated with CO2 emission, no significantly positive correlation was found between local air pollutants emission reductions and CO2 emission reductions, indicating that co-control effects were poor in general. By using the co-control effect coordinate system, qualitative evaluation showed that less than half of the sample cities could achieve co-control of the total amount of CO2 and local air pollutants. By employing the indicator of emission reduction equivalence (EReq), quantitative evaluation showed that the co-control level of the sample cities improved in 2015–2018 compared with 2012–2015. Further regression analysis showed that, reducing coal consumption and economic development significantly enhanced the co-control performance of the observed cities. The present case study proved that the proposed methods for evaluation and comparison of the city co-control performance works well, and can be used in other countries and regions to promote global cities racing to carbon and local air pollutants co-control.

A thorough understanding of chemical composition, particle pH, and pollutant emissions is essential to address the climate and human health effects of atmospheric particles. In this study, we used a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and Scanning Mobility Particle Sizer (SMPS) to characterize the composition of submicron particles. Moreover, we applied the ISORROPIA-II model to analyze the particle acidity effect on the compositional characterization of submicron particles from December 22, 2016 to January 7, 2017 in Albany, New York, USA. The results indicated that aerosols with mobility diameter from SMPS in the range 200–400 nm were the main contributors to the mass during the measurement period. The dominance of organics (47%) and sulfate (16%) was similar to previous observations in the eastern United States in Winter 2015, while the fraction of nitrate (23%) was much higher. Moreover, nitrate could easily form at colder temperatures and lower RH levels even when there were more acidic particle periods during the measurement period in Albany. The ISORROPIA-II model indicated that there were more acidic particles, which was estimated using pH values. Lower temperature conditions tended to favor nitrate formation. The nitrate concentration exceeded that of sulfate in the measurement period, even though the SO2 and NOx emissions were similar. The organics in submicron particles were strongly influenced by the local emissions in winter. However, the inorganic compounds in submicron particles could be derived from regional transport as their pollution sources originated from different directions. This may help strategize emission reductions in the future.

Air pollution in urban areas is a huge concern that demands an efficient air quality control to ensure health quality standards. The hotspots can be located by increasing spatial distribution of ambient air quality monitoring for which the low-cost sensors can be used. However, it is well-known that many factors influence their results. For low-cost Particulate Matter (PM) sensors, high relative humidity can have a significant impact on data quality. In order to eliminate or reduce the impact of high relative humidity on the results obtained from low-cost PM sensors, a low-cost dryer was developed and its effectiveness was investigated. For this purpose, a test chamber was designed, and low-cost PM sensors as well as professional reference devices were installed. A vaporizer regulated the humid conditions in the test chamber. The low-cost dryer heated the sample air with a manually adjustable intensity depending on the voltage. Different voltages were tested to find the optimum one with least energy consumption and maximum drying efficiency. The low-cost PM sensors with and without the low-cost dryer were compared. The experimental results verified that using the low-cost dryer reduced the influence of relative humidity on the low-cost PM sensor results., Bundesministerium für Bildung und Forschung

Many countries shut their borders, imposed nationwide lockdown, and restricted several anthropogenic activities to arrest the spread of COVID-19. In the present study, the concentration of several air pollutants (PM10, PM2.5, NO2, NH3, SO2, CO and O3) during different phases of lockdown from monitoring stations of Patna was analyzed to assess the effect of lockdown restriction on air quality. Reduction in PM2.5, NH3, NO2, PM10 and CO concentration was observed by 59.79%, 58.2%, 49.49%, 39.57% and 24.04%, respectively during the lockdown period. National Air Quality Index (NAQI) value in the year 2020 had been observed to lower by 57.88% compared to the year 2019, during the same period. A more significant fall in the concentration of air pollutants was observed during the early phase of post-lockdown compared to the late stages of postlockdown. The study reflects the significance of restriction on anthropogenic activities in improving air quality and provides clues for future action plans for improving air quality.

Building mechanical ventilation systems are a major driver of indoor air chemistry as their design and operation influences indoor ozone (O3) concentrations, the dilution and transport of indoor-generated volatile organic compounds (VOCs), and indoor environmental conditions. Real-time VOC and O3 measurements were integrated with a building sensing platform to evaluate the influence of mechanical ventilation modes and human occupancy on the dynamics of skin oil ozonolysis products (SOOPs) in an office in a LEED-certified building during the winter. The ventilation system operated under variable recirculation ratios (RRs) from RR = 0 (100% outdoor air) to RR = 1 (100% recirculation air). Time-resolved source rates for 6-methyl-5-hepten-2-one (6-MHO), 4-oxopentanal (4-OPA), and decanal were highly dynamic and changed throughout the day with RR and occupancy. Total SOOP source rates during high-occupancy periods (10:00-18:00) varied from 2500-3000 μg h-1 when RR = 0.1 to 6300-6700 μg h-1 when RR = 1. Source rates for gas-phase reactions, outdoor air, and occupant-associated emissions generally decreased with increasing RR. The recirculation air source rate increased with RR and typically became the dominant source for RR > 0.5. SOOP emissions from surface reservoirs were also a prominent source, contributing 10-50% to total source rates. Elevated per person SOOP emission factors were observed, potentially due to multiple layers of soiled clothing worn during winter.

Sphagnum mosses are used for biomonitoring air pollution. In 2019, samples were taken from two peat bogs areas in Germany and two in Slovenia to determine differences in their levels of potentially toxic elements (PTE). The Coronavirus Disease (COVID-19) lockdown caused a global decrease in air pollution. Therefore, we repeated the monitoring in 2020 to see if this was also reflected in moss composition. Despite the variability within bogs and the areas, it is possible to distinguish the degree of air pollution between the two countries. In comparison to 2019, the German mosses have higher contents of almost all elements and the Slovenian are enriched in Cr and Hg in 2020. Comparison of the PTE contents, their ratios to Sc, and the enrichment factors show that the COVID-19 lockdown led to a decrease in long-range pollutants bound to finest particles and increased the influence of local soil dusting. The effect prevailed over lower precipitation in 2020 compared to 2019. Transport and industry continued to contribute significantly to contamination. Sphagnum mosses proved to be good indicators of the spatial and temporal extent of pollution. Even relatively short periods of lower air pollution are reflected in moss PTE contents.

Green vegetation enrichment is a cost-effective technique for reducing atmospheric pollution. Fifteen common tropical plant species were assessed for identifying their air pollution tolerance, anticipated performance, and metal accumulation capacity at Jharia Coalfield and Reference (JCF) site using Air Pollution Tolerance Index (APTI), Anticipated Performance Index (API), and Metal Accumulation Index (MAI). Metal accumulation efficiencies were observed to be highest for Ficus benghalensis L. (12.67mg/kg) and Ficus religiosa L. (10.71 mg/kg). The values of APTI were found to be highest at JCF for F. benghalensis (APTI: 25.21 ± 0.95), F. religiosa (APTI: 23.02 ± 0.21), Alstonia scholaris (L.) R. Br. (APTI: 18.50 ± 0.43), Mangifera indica L. (APTI: 16.88 ± 0.65), Azadirachta indica A. Juss. (APTI: 15.87 ± 0.21), and Moringa oleifera Lam. (APTI: 16.32 ± 0.66). F. benghalensis and F. religiosa were found to be excellent performers to mitigate air pollution at JCF as per their API score. Values of MAI, APTI, and API were observed to be lowest at reference sites for all the studied plant species due to absence of any air polluting sources. The findings revealed that air pollution played a significant impact in influencing the biochemical and physiological parameters of plants in a contaminated coal mining area. The species with the maximum MAI and APTI values might be employed in developing a green belt to minimize the levels of pollutants into the atmosphere.

Improving the NOx conversion efficiency and particulate combustion efficiency under cold-start conditions (low-temperature conditions) is still the main challenge faced by catalytic gasoline particulate filter systems (CGPFs). In this study, the physical and mathematical models of novel CGPFs are proposed based on the computational fluid dynamics software. Then, the models are validated based on experiments, and the performances of conventional and novel CGPFs are analyzed comparatively. The comparison conclusions indicate that the NOx conversion efficiency of the novel CGPFs increases by 3.2% and the particulate combustion efficiency increases by 2.7% under the same operating condition. Finally, the effects of exhaust flow vf, exhaust oxygen mass fraction Co, exhaust NO mass fraction CNO, and electric heating power Pe on the NOx conversion efficiency and particulate combustion efficiency are investigated. The weights of each influencing parameter on the NOx conversion efficiency and particulate combustion efficiency are explored by orthogonal tests. The conclusions show that the NOx conversion efficiency is increased by 3.6% and the particulate combustion efficiency is increased by 16.7% compared to the initial condition. This study has an important reference value for improving the purification efficiency of vehicle emission under cold-start conditions.

Traffic as the main source of urban air pollution created severe problems for human health and sustainability. To propose a bottom-up method in emissions reduction, accurate emission inventories of vehicles in a medium-sized city are developed. Traffic emission factors were obtained using traffic flow data, traffic control cameras, and International Vehicle Emission (IVE) model to calculate CO, VOCs, NOx, SOx, and PM of passenger cars, taxis, and urban buses emission inventory. Annual overall emissions of CO, VOCs, NOx, SOx, and PM pollutants, respectively, are 346, 20.9, 25, 44.4, and 0.5 kt/year. VOC and CO emissions in the start-up phase are in the scale of the running phase, while NOx, SOx, and PM allocate much less than the running phase. The highest emission value of SOx and PM occurs in arterials while CO, VOC, and NOx in highways. Eight renovation scenarios have been designed to evaluate their environmental and economic efficiency. Two scenarios entitled "renovation of carbureted, Euro 1 and Euro 2 LDV" and "renovation of high mileage Euro 1 and Euro 2 standard urban buses" showed the highest decrease in pollution emission and pollution social costs. For these two important scenarios, implementation costs were calculated at 477 and 46 M$, while social costs decrease are calculated to be 172.6 and 77.5 M$, respectively. Renovation of vehicles could benefit both the government and society by reducing fuel consumption and pollutant emission. The emission mitigation scenarios considering mobile sources could be a guide for adopting policies in developing countries. Governmental and social cost-share and governmental and social repayment because of fuel-saving costs have also been calculated.

The Southeastern Anatolia Region (SEAR), the third-lowest mean annual precipitation region in Turkey, has semi-arid climate and plateau characteristics. The proximity of the region to North Africa and the Middle East dust source areas enables long-range transport of desert dust particles toward the SEAR by strong winds. Among the other dust source regions, the Arabian Peninsula has a crucial role in terms of affecting the SEAR with a high-annual frequency and high dust concentration values. We investigated the atmospheric patterns of three extreme Arabian dust episodes that affect the SEAR in this study. Dust episodes were determined using present weather (SYNOP) codes of ten stations in the SEAR during the 2014–2019 period. The source regions were found using HYSPLIT backward trajectory analysis. In this study, we benefited from synoptic maps, in situ PM10 observations, numerical simulations of the WRF-Chem model, and MODIS satellite images to analyze the extreme dust episodes. The results showed that the surface low pressure over the Persian Gulf and strong southerly winds at the 700-hPa level enabled the transport of dust particles from the surface to the mid-atmospheric levels. If the center of the upper-level ridge extended from Saudi Arabia to southern Turkey, the atmospheric blocking mechanism prevented the dispersion of dense dust particles from the SEAR to its surrounding, which caused the observation of high dust concentrations in the SEAR. In general, the WRF-Chem model outputs are in good agreement with ground-based PM10 concentrations and MODIS true-color images in terms of temporal and spatial distributions of dust concentrations.

Respirable Crystalline Silica (RCS) is a hazardous substance with known effects that can be well correlated with exposure levels that still persist in many traditional sectors, such as construction or stone processing. In the past decade, exposure scenarios for RCS have been found in the sector of artificial stone processing. The aim of this study is to evaluate the levels of RCS in facilities specialized in the production of artificial stone countertops and other accessories for the furnishing of kitchens, bathrooms, and offices after the introduction of some preventive technical measures such as wet processing or local exhaust ventilation systems. The study involved 51 subjects in four facilities. Personal silica exposure assessment was carried out using GS3 cyclones positioned in the breathing zone during the work shift. Quantitative determination of silica was carried out by X-ray diffraction analysis. Respirable dust levels were in the range 0.046-1.154 mg/m3 with RCS levels within the range

In order to effectively analyze and explore the socio-economic impact of haze pollution, the article constructs a comprehensive two-stage decomposition model to verify that technological progress plays a key role in controlling haze pollution. And for the first time, a macro-level research framework for the rebound effect of haze pollution has been constructed to compare and analyze the heterogeneity of the rebound effect of technological progress in different industries in different regions. The study found that (1) during the period 2000-2017, haze pollution situation deteriorated. Economic effects were the main reasons for haze pollution. Among these effects, technological progress was the main driving force for haze control, followed by the emission intensity during 2000-2011 and the reduction of industrial structure since 2014. (2) The significant drive of emission reduction is in the secondary industry, showing a trend of first increasing and then decreasing. Besides, there was a difference in spatial distribution, which shows an increased trend from east to west. (3) The rebound effect of haze pollution at the macro level in China presented high-level fluctuations, and there were certain spatial distribution differences. However, due to the convergence of technological development stages, regional differences have a gradual convergence trend. In the future, in the process of haze control, it is necessary to increase support for technological innovation, implement energy total control and price reform, promote technological progress, and implement differentiated haze reduction policies to solve problems according to local conditions.

Volatile chemical products (VCPs) are a significant source of reactive organic carbon emissions in the United States, with a substantial fraction (>20% by mass) serving as secondary organic aerosol (SOA) precursors. Here, we incorporate a new nationwide VCP inventory into the Community Multiscale Air Quality (CMAQ) model, with VCP-specific updates to better model air quality impacts. Model results indicate that VCPs most enhance anthropogenic SOA in densely populated areas, with population-weighted annual average SOA increasing 15 – 30% in Southern California and New York City due to VCP emissions (contribution of 0.2 – 0.5 μg m(−3)). Annually, VCP emissions enhance total population-weighted PM(2.5) by ~5% in California, ~3% in New York, New Jersey, and Connecticut, and 1 – 2% in most other states. While the maximum daily 8-hr ozone enhancements from VCP emissions are more modest, their influence can cause a several ppb increase on select days in major cities. Printing Inks, Cleaning Products, and Paints & Coatings product use categories contribute ~75% to the modeled VCP-derived SOA and Cleaning Products, Paints & Coatings, and Personal Care Products contribute ~81% to the modeled VCP-derived ozone. Overall, VCPs enhance multiple criteria pollutants throughout the United States, with the largest impacts in urban cores.

Epidemiological studies use direct and indirect methods to estimate exposure to air pollutants. In this paper, we compared the exposure to NO2 given by dispersion modeling and a fixed monitoring station and personal monitors during the daily routine of twenty-one children. Indoor-outdoor (I/O) ratios were used to represent differences between indoor and outdoor environments. A sensitivity test was performed to assess the impact of this parameter. Questionnaires were used to obtain subjects’ routines during campaigns. The results obtained using dispersion models agree with the individual differences in exposure assessed by personal monitors — if compared to a method relying solely on the monitoring station. Nevertheless, an overestimation occurred for children living near roadways. The exposure results revealed higher sensitivity to I/O ratios used than to children’s pathways between their usual destinations. The time spent outdoors (or indoors) and the concentration variation at the urban microscale (

This study investigated the impact of outdoor air pollutants on indoor air quality in a high-rise building, considering factors related to the seasons and air infiltration. Further, the impact of atmospheric weather conditions on air infiltration has been analysed in a downtown area of Suzhou, China. The influence of the outdoor air pollution rate on indoor air quality in the office building was investigated based on onsite measurements and computer simulations. Results showed that the impact of outdoor air pollutants on indoor air quality was highest in winter, followed by spring, autumn and summer. Furthermore, multiple factors, which affect the indoor air quality in a high-rise building, have been further investigated in this study, including stack effect, wind effect, infiltration rate, outdoor air pollution rate, seasonal change and air filter efficiency. The significant influence of these factors on the indoor air quality level with floor height variations has been verified. Based on the analysis, a high-efficiency filter is recommended to maintain healthy indoor air quality. Meanwhile, a double-filter system is required if a building is exposed to heavily polluted outdoor air considering the most substantial impact of outdoor air pollutants on indoor air quality in winter. Moreover, a numerical model of steady-state indoor PM2.5 concentration was established to determine the suitable air filter efficiency and airtightness. This work was supported by the Research Development Fund (RDF 15–02-32) of Xi’an Jiaotong – Liverpool University, Zhejiang Provincial Natural Science Foundation (LY19E080001), the UK ICE Research Development Enabling Fund (ICE_RDF_2020), and the Department of Civil Engineering and Energy Technology of Oslo Metropolitan University.

A monitoring campaign, the first of this kind for a heavy traffic urban area of Vietnam, was conducted which generated nearly 200 daily filter samples of PM2.5, PM10, and black carbon (BC), 1300 online hourly PMx (PM10, PM2.5, and PM1), 900 hourly/bi-hourly BTEX data, 700 h of traffic counts, and online meteorology records. PMx and BTEX levels show large horizontal gradients across this small urban area of 300 m width suggesting that the pollution data should be generated with sufficient spatial resolutions for assessment of the exposure and health effects. This paper focuses on analyzing PMx with reference to the previously published BTEX to provide a more complete picture of the traffic-related pollution in the area. Spatio-temporal variations of pollutants are analyzed in relation to traffic flows and fleet compositions, weekday-weekend effects, local and regional meteorology. PM10 and BTEX levels had larger variations between the sites indicating their stronger associations with the traffic activities than the finer particles. Twenty-four-hour (24 h) PM2.5 levels ranged between 19 and 191 µg/m3 with high PM1/PM2.5 ratios of above 0.8 at ambient site (AA) and above 0.7 at roadsides. Multivariate relationship analysis (PCA) for the bi-hourly datasets of meteorology, traffic flows, and pollutant levels indicated overwhelming influence of on-road traffic fleet compositions on the roadside pollutants levels. At AA, PCA results showed a complex interaction between local emissions, meteorological conditions, and regional/long-range transport. Higher pollution levels were associated with the airmass types having the continental origin and pathways.

Improving our understanding of air pollutant emissions from the asphalt industry is critical for the development and implementation of pollution control policies. In this study, the spatial distribution of potential maximum emissions of volatile organic compounds (VOCs) in the complete life cycle of asphalt mixtures, as well as the particulate matter (PM), asphalt fume, nonmethane hydrocarbons (NMHCs), VOCs, and benzoapyrene (BaP) emissions from typical processes (e.g., asphalt and concrete mixing stations, asphalt heating boilers, and asphalt storage tanks) in asphalt mixing plants, were determined in Beijing in 2017. The results indicated that the potential maximum emissions of VOCs in the complete life cycle of asphalt mixtures were 18,001 ton, with a large contribution from the districts of Daxing, Changping, and Tongzhou. The total emissions of PM, asphalt fume, NMHC, VOCs, and BaP from asphalt mixing plants were 3.1, 12.6, 3.1, 23.5, and 1.9 × 10−3 ton, respectively. The emissions of PM from asphalt and concrete mixing stations contributed the most to the total emissions. The asphalt storage tank was the dominant emission source of VOCs, accounting for 96.1% of the total VOCs emissions in asphalt mixing plants, followed by asphalt heating boilers. The districts of Daxing, Changping, and Shunyi were the dominant regions for the emissions of PM, asphalt fume, NMHC, and BaP, while the districts of Shunyi, Tongzhou, and Changping contributed the most emissions of VOCs.

Escalating emissions of several air pollutants over South Asia could play a detrimental role in the regional and global atmosphere. Therefore, it is necessary to investigate these emissions within the boundary layer and at higher heights utilizing satellite data that are more inclusionary, where limited in situ observations are available. Here, we utilize the Infrared Atmospheric Sounding Interferometer (IASI), Ozone Monitoring Instruments (OMI), TROPOspheric Monitoring Instrument (TROPOMI), and Global Ozone Monitoring Experiment (GOME-2) hyperspectral satellite data to assess the changes in emission sources during Indian lockdown with a primary focus on the tropospheric profiles of ozone and carbon monoxide (CO). A significant reduction (> 20%) in the tropospheric ozone was seen over northern and northeast regions compared to 2018, while a dramatic increase (> 20%) compared to 2019 was seen. The subtropical dynamics mainly contributed to the increased ozone over the northern region. An analysis of the ozone production regime showed mostly NO2 limited regime over the major part of India and VOC limited regime over thermal power plants regions. Unlike in the boundary layer, where CO showed reduction (15–20%), CO profiles showed a consistent increase (as high as 31%) in the free troposphere over the majority of cities and thermal power plants. The CO total column also showed an increase (~ 20%) over central and western India and a slight decrease (5%) over northern India. Similar to CO, an increase (~ 15%) of NO2 column over the western region was observed particularly compared to 2019. However, unlike ozone and CO, reduction of tropospheric NO2 columns was seen over the major part of India, with the highest reduction over northern regions (20–52%). Furthermore, homogeneous yearly differences (> 30%) between OMI and TROPOMI NO2 observations were also seen distinctly over the remote areas. Contrary to surface-based studies, the present study shows an increase in CO, ozone (decrease), and NO2 at several locations and in the free troposphere during the lockdown. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-17441-2.

The year 2020 was atypical due to the pandemic caused by the SARS-CoV-2 virus (COVID-19), providing a unique opportunity to understand changes in air quality due to the reduction in urban activity. Therefore, the aim of the present study was to perform an integrated evaluation on the influence of the effects of the 2020 pandemic on air quality in the city of Fortaleza, investigating levels of PM2.5, PM10, NO2, NO, SO2, CO, and O3, corresponding health risks, as well as the influence of meteorological variables and urban activity. In all phases analyzed, significant reductions were found in NOx, NO, NO2, and CO. A considerable reduction in PM2.5 and PM10 was found in the early phases, with an increase in the later phases. These findings are explained by the nearly 50% reduction in vehicular traffic and the consequent reduction in fossil fuel emissions, mainly in the partial lockdown and total lockdown periods, as well as reductions in commercial (stores/shops) and industrial activities. The variation in O3 was initially non-significant, followed by a considerable increase in the last three phases analyzed; this increase was influenced by changes in temperature and the incidence of sunlight. SO2 concentrations increased in the period studied, demonstrating that the vehicular fleet, local commerce, and other activities are not the predominant sources of this compound. Estimated health risks were reduced by half during the lockdown period, especially for non-smokers, followed by a drastic increase in the last three phases. The planetary boundary layer was positively correlated with O3 and PM10 and negatively correlated with NOx, NO2, and NO, indicating its influence on the distribution of pollutants in the lower atmosphere and, consequently, air quality.

The COVID-19 pandemic has a close relationship with local environmental conditions. This study explores the effects of climate characteristics and air pollution on COVID-19 in Isfahan province, Iran. A number of COVID-19 positive cases, main air pollutants, air quality index (AQI), and climatic variables were received from March 1, 2020, to January 19, 2021. Moreover, CO, NO2, and O3 tropospheric levels were collected using Sentinel-5P satellite data. The spatial distribution of variables was estimated by the ordinary Kriging and inverse weighted distance (IDW) models. A generalized linear model (GLM) was used to analyze the relationship between environmental variables and COVID-19. The seasonal trend of nitrogen dioxide (NO2), wind speed, solar energy, and rainfall like COVID-19 was upward in spring and summer. The high and low temperatures increased from April to August. All variables had a spatial autocorrelation and clustered pattern except AQI. Furthermore, COVID-19 showed a significant association with month, climate, solar energy, and NO2. Suitable policy implications are recommended to be performed for improving people’s healthcare and control of the COVID-19 pandemic. This study could survey the local spread of COVID-19, with consideration of the effect of environmental variables, and provides helpful information to health ministry decisions for mitigating harmful effects of environmental change. By means of the proposed approach, probably the COVID-19 spread can be recognized by knowing the regional climate in major cities. The present study also finds that COVID-19 may have an effect on climatic condition and air pollutants. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-17535-x.

Annual global satellite-based estimates of fine particulate matter (PM2.5) are widely relied upon for air-quality assessment. Here, we develop and apply a methodology for monthly estimates and uncertainties during the period 1998-2019, which combines satellite retrievals of aerosol optical depth, chemical transport modeling, and ground-based measurements to allow for the characterization of seasonal and episodic exposure, as well as aid air-quality management. Many densely populated regions have their highest PM2.5 concentrations in winter, exceeding summertime concentrations by factors of 1.5-3.0 over Eastern Europe, Western Europe, South Asia, and East Asia. In South Asia, in January, regional population-weighted monthly mean PM2.5 concentrations exceed 90 μg/m3, with local concentrations of approximately 200 μg/m3 for parts of the Indo-Gangetic Plain. In East Asia, monthly mean PM2.5 concentrations have decreased over the period 2010-2019 by 1.6-2.6 μg/m3/year, with decreases beginning 2-3 years earlier in summer than in winter. We find evidence that global-monitored locations tend to be in cleaner regions than global mean PM2.5 exposure, with large measurement gaps in the Global South. Uncertainty estimates exhibit regional consistency with observed differences between ground-based and satellite-derived PM2.5. The evaluation of uncertainty for agglomerated values indicates that hybrid PM2.5 estimates provide precise regional-scale representation, with residual uncertainty inversely proportional to the sample size.

Buses constitute a significant source of air pollutant emissions in cities. In this study, we present real-world NOx emissions from 97 diesel-hybrid buses measured using on-board diagnostic systems over 44 months and 6.35 million km in London. Each bus had previously been retrofitted with a selective catalytic reduction (SCR) aftertreatment system to reduce emissions of nitrogen oxides (NOx). On average, parallel hybrid (PH) and series hybrid (SH) buses emitted 3.80 g of NOx/km [standard deviation (SD) of 1.02] and 2.37 g of NOx/km (SD of 0.51), respectively. The SCR systems reduced engine-out emissions by 79.8% (SD of 5.0) and 87.2% (SD of 2.9) for the PHs and SHs, respectively. Lower ambient temperatures (0–10 °C) increased NOx emissions of the PHs by 24.2% but decreased NOx emissions of the SHs by 27.9% compared to values found at more moderate temperatures (10–20 °C). To improve emissions inventories, we provide new distance-based NOx emissions factors for different ranges of ambient temperature. During the COVID-19 pandemic, the emissions benefits of reduced congestion were largely offset by more frequent route layovers leading to lower SCR temperatures and effectiveness. This study shows that continuous in-service measurements enable quantification of real-world vehicle emissions over a wide range of operations that complements conventional testing approaches.

Cooking organic aerosol (COA) is an important source of particulate pollutants in urbanized regions. Yet, the diversity and complexity of COA components make direct identification and quantification of COA difficult. In this study, we conducted collocated OA measurements with an aerosol mass spectrometer (AMS) and a thermal desorption aerosol gas chromatography-mass spectrometer (TAG) in Shanghai. Cooking molecular tracers (e.g., C18 fatty acids, azelaic acid) measured by TAG provide unambiguous source information for evaluating the tracer ion (C6H10O+, m/z 98) used for identification and apportionment of COA in AMS analysis. Based on the collocated AMS and TAG measurements, two COA factors, namely, a primary COA (PCOA) and an oxygenated COA (OCOA) produced from rapid oxygenation of freshly emitted PCOA, were identified. Criteria for identifying COA factors from AMS analysis with different oxygenation levels are proposed, i.e., characteristic mass spectra, temporal variations, etc. Furthermore, two positive matrix factorization approaches, namely, AMS-PMF and the molecular marker (MM)-PMF, were compared for COA quantification, where high consistency was found with the contribution of COA to total PM2.5 mass estimated to be 9 ± 7% by AMS-PMF and 6 ± 5% by the MM-PMF. Our study highlights the important impacts of cooking activities on air quality in urban areas. We also demonstrate the advantage of conducting collocated measurements using multiple high time resolution mass spectrometric techniques in advancing our understanding of atmospheric OA chemistry and improving the accuracy of source apportionment.

The coronavirus disease (COVID-19) is a highly transmitted disease that spreads all over the globe in a short period. Environmental pollutants are considered one of the carriers to spread the COVID-19 pandemic through health damages. Carbon emissions, PM2.5 emissions, nitrous oxide emissions, GHG, and other GHG emissions are mainly judged separately in the earlier studies in different economic settings. The study hypothesizes that environmental pollutants adversely affect healthcare outcomes, likely to infected people by contagious diseases, including coronavirus cases. The subject matter is vital to analyze the preventive healthcare theory by using different environmental pollutants on the COVID-19 factors: total infected cases, total death cases, and case fatality ratio, in a large cross-section of 119 countries. The study employed the generalized least square (GLS) method for robust inferences. The results show that GHG and CO2 emissions are critical factors likely to increase total coronavirus cases and death rates. On the other hand, nitrous oxide, carbon, and transport emissions increase the case fatality ratio through healthcare damages. The study concludes that stringent environmental policies and improving healthcare infrastructure can control coronavirus cases across countries.

Complying with stricter emissions standards, a new generation of heavy-duty trucks (HDTs) has gradually increased its market share and now accounts for a large percentage of on-road mileage. The potential to improve air quality depends on an actual reduction in both emissions and subsequent formation of secondary pollutants. In this study, the emissions in real-world traffic from Euro VI-compliant HDTs were compared to those from older classes, represented by Euro V, using high-resolution time-of-flight chemical ionization mass spectrometry. Gas-phase primary emissions of several hundred species were observed for 70 HDTs. Furthermore, the particle phase and secondary pollutant formation (gas and particle phase) were evaluated for a number of HDTs. The reduction in primary emission factors (EFs) was evident (∼90%) and in line with a reduction of 28–97% for the typical regulated pollutants. Secondary production of most gas- and particle-phase compounds, for example, nitric acid, organic acids, and carbonyls, after photochemical aging in an oxidation flow reactor exceeded the primary emissions (EFAged/EFFresh ratio ≥2). Byproducts from urea-selective catalytic reduction systems had both primary and secondary sources. A non-negative matrix factorization analysis highlighted the issue of vehicle maintenance as a remaining concern. However, the adoption of Euro VI has a significant positive effect on emissions in real-world traffic and should be considered in, for example, urban air quality assessments., When more stringent Euro VI emission standards replaced Euro V standards, the emissions and secondary formation of both regulated and non-regulated air pollutants reduced significantly.

We analyzed pollution plumes originating from ships using liquefied natural gas (LNG) as a fuel. Measurements were performed at a station located on the Utö island in the Baltic Sea during 2015–2021 when vessels passed the station along an adjacent shipping lane and the wind direction allowed the measurements. The ratio of the measured concentration peaks ΔCH4/ΔCO2 ranged from 1% to 9% and from 0.1% to 0.5% for low and high pressure dual fuel engines, respectively. The ratio of the measured concentration peaks of ΔNOx/ΔCO2 varied between 0.5‰ and 8.7‰, which was not explained by engine type. The results were consistent with previously measured on-board or test-bed values for the corresponding ratios of emissions. While the methane emissions from high pressure dual fuel engines were found to fulfill the goal of reducing the climatic impacts of shipping, the emissions originating from low pressure dual fuel engines were found to be substantially high, with a potential for increased climatic impacts compared with using traditional marine fuels. Taking only the global warming potential into account, we can suggest a limit value for the methane emissions; the ratio of the emissions ΔCH4/ΔCO2 originating from LNG powered ships should not exceed 1.4%., Remote marine air-quality measurements show significant climate relevant methane emissions from ships using liquefied natural gas as a fuel.

Dust is one of the air pollutants with a high level of toxicity and plays a significant role in the destruction of ambient air. Dust contains solid particles that can cause various respiratory diseases and can pollute the air. Dust will enter human lungs if a person breathes air that prevents dust, especially dust that has a size of 1 to 3 microns which will then stick to the alveoli. This study aims to determine the level of dust in the environment of the anting limestone factory in Makassar. This type of research uses an analytic survey with a cross-sectional design. Samples were taken by purposive sampling as many as 35 samples. The results of the study obtained in the acting lime factory are the work period> 5 years consisting of 28 workers 80%, while 8 hours/day 31 workers 31.3%, while

Exposure to poor air quality is considered a major influence on the occurrence of cardiovascular and respiratory diseases. Air pollution has also been linked to the severity of the effects of epidemics such as COVID-19 caused by the SARS-CoV-2 virus. Epidemiological studies require datasets of the long-term exposure to air pollution. We present the APExpose_DE dataset, a long-term (2010–2019) dataset providing ambient air pollution metrics at yearly time resolution for NO2, NO, O3, PM10 and PM2.5 at the NUTS-3 spatial resolution level for Germany (corresponding to the Landkreis or Kreisfreie Stadt in Germany, 402 in total)., Measurement(s)air pollutionTechnology Type(s)digital curation • computational modeling techniqueSample Characteristic - LocationGermany Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.16680412

Air quality improvements pollution changes due to COVID-19 restrictions have been reported for many urban developments and large metropolitan areas, but the respective impacts at rural and remote zones are less frequently analysed. This study evaluated air pollution changes across all Portugal (68 stations) considering all urban, suburban and rural zones. PM10, PM2.5, NO2, SO2, ozone was analysed in pre-, during, and post-lockdown period (January–May 2020) and for a comparison also in 2019. NO2 was the most reduced pollutant in 2020, which coincided with decreased traffic. Significant drop (15–71%) of traffic related NO2 was observed specifically during lockdown period, being 55% for the largest and most populated region in country. PM was affected to a lesser degree (with substantial differences found for largely populated areas (Lisbon region ~ 30%; North region, up to 49%); during lockdown traffic-related PM dropped 10–70%. PM10 daily limit was exceeded 50% less in 2020, with 80% of exceedances before lockdown period. SO2 decreased by 35%, due to suspended industrial productions, whereas ozone concentrations slightly (though not significantly) increased (83 vs. 80 µg m–3).

Nitrogen dioxide (NO2) is one of the main air pollutants, formed due to both natural and anthropogenic processes, which has a significant negative impact on human health. The COVID-19 pandemic has prompted countries to take various measures, including social distancing or stay-at-home orders. This study analyzes the impact of COVID-19 lockdown measures on nitrogen dioxide (NO2) changes in Central Asian countries. Data from TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite, as well as meteorological data, make it possible to assess changes in NO2 concentration in countries and major cities in the region. In particular, the obtained satellite data show a decreased tropospheric column of NO2. Its decrease during the lockdown (March 19-April 14) ranged from - 5.1% (Tajikistan) to - 11.6% (Turkmenistan). Based on the obtained results, it can be concluded that limitations in anthropogenic activities have led to improvements in air quality. The possible influence of meteorology is not assessed in this study, and the implied uncertainties cannot be quantified. In this way, the level of air pollution is expected to decrease as long as partial or complete lockdown continues.

Solid fuels used for cooking, heating, and lighting are major emission sources of many air pollutants, specifically PM2.5 and black carbon, resulting in adverse environmental and health impacts. At the same time, the transition from using residential solid fuels toward using cleaner energy sources can result in significant health benefits. Here, we briefly review recent research progress on the emissions of air pollutants from the residential sector and the impacts of emissions on ambient and indoor air quality, population exposure, and health consequences. The major challenges and future research priorities are identified and discussed.

Zhengzhou is one of the most haze-polluted cities in Central China with high organic carbon emission, which accounts for 15%-20% of particulate matter (PM2.5) in winter and causes significantly adverse health effects. Volatile organic compounds (VOCs) are the precursors of secondary PM2.5 and O3 formation. An investigation of characteristics, sources and health risks assessment of VOCs was carried out at the urban area of Zhengzhou from 1st to 31st December, 2019. The mean concentrations of total detected VOCs were 48.8 ± 23.0 ppbv. Alkanes (22.0 ± 10.4 ppbv), halocarbons (8.1 ± 3.9 ppbv) and aromatics (6.5 ± 3.9 ppbv) were the predominant VOC species, followed by alkenes (5.1 ± 3.3 ppbv), oxygenated VOCs (3.6 ± 1.8 ppbv), alkyne (3.5 ± 1.9, ppbv) and sulfide (0.5 ± 0.9 ppbv). The Positive Matrix Factorization model was used to identify and apportion VOCs sources. Five major sources of VOCs were identified as vehicular exhaust, industrial processes, combustion, fuel evaporation, and solvent use. The carcinogenic and non-carcinogenic risk values of species were calculated. The carcinogenic and non-carcinogenic risks of almost all air toxics increased during haze days. The total non-carcinogenic risks exceeded the acceptable ranges. Most VOC species posed no non-carcinogenic risk during three haze events. The carcinogenic risks of chloroform, 1,2-dichloroethane, 1,2-dibromoethane, benzyl chloride, hexachloro-1,3-butadiene, benzene and naphthalene were above the acceptable level (1.0 × 10−6) but below the tolerable risk level (1.0 × 10−4). Industrial emission was the major contributor to non-carcinogenic, and solvent use was the major contributor to carcinogenic risks.

This work evaluated the nitrogen oxide (NOx) emissions of 277 heavy-duty diesel vehicles (HDDVs) from three portable emission measurement system testing programs. HDDVs in these programs were properly maintained before emission testing, so the malfunction indicator lamp (MIL) was not illuminated. NOx emissions of some HDDVs were significantly higher than the certification standard even during hot operations where exhaust temperature was ideal for selective catalytic reduction to reduce NOx. For engines certified to the 0.20 g/bhp-hr NOx standard, hot operation NOx emissions increased with engine age at 0.081 ± 0.016 g/bhp-hr per year. The correlation between emissions and mileage was weak because six trucks showed extraordinarily high apparent emission increase rates reaching several multiples of the standard within the first 15,000 miles of operation. The overall annual increase in NOx emissions for the HDDVs in this study was two-thirds of what was observed in real-world emissions for HDDVs at the Caldecott Tunnel over the past decade. The vehicles at the Caldecott Tunnel would include those without proper maintenance, and the inclusion of these vehicles possibly explains the difference in the rate of emission increase. The results suggest that HDDVs need robust strategies to better control in-use NOx emissions.