VOC Sources Research Articles

Uncovering the characteristics of air pollutants emission in industrial parks and analyzing emission reduction potential: case studies in Henan, China

Industrial parks contribute greatly to China’s economic development while emitting huge air pollutants. It is necessary to study the characteristics of air pollutant emissions in industrial parks. In this study, emission inventories for 11 industrial parks were established. Meanwhile, the source emission and spatial distribution characteristics of the industrial park were analyzed. The cluster analysis was used to classify these parks into “4Hs”, “Mixed” and “4Ls” parks. “4Hs”, “Mixed” and “4Ls” represent that the levels of energy intensity, economic proportion of energy-intensive industries, coal proportion and pollution performance value are high, medium and low in turn. Then three emission reduction measures were set up to estimate the emission reduction potential and environmental impacts. The results show that: (1) the emissions of SO2, NOx, CO, PM10, PM2.5, VOCs and NH3 of 11 industrial parks in 2017 were 11.2, 23.1, 30.8, 8.3, 3.5, 5.1, and 1.1 kt, respectively. (2) Power plants were the largest source of SO2 and NOx emissions, and industrial processes were the largest emission source of CO, PM10, PM2.5, VOCs and NH3. (3) “4Hs” parks with traditional energy-intensive industries as the leading industries should be the emphasis of air pollutant emission reduction. (4) Through the optimal emission reduction measures, SO2, NOx, PM10, PM2.5 and VOCs were reduced by 81, 46, 51, 46 and 77%, respectively. Environmental impact reductions include 1.6 kt SO2eq acidified gas emissions, 1.4 kt PO43−eq eutrophication substances, 4.2 kt PM10eq atmospheric particulate emissions, 7.0 kt 1,4-DCEeq human toxic substances, and 5.2 kt PM2.5 eq breathing Inorganic. This study is helpful to understand the characteristics of air pollutants emissions in industrial parks and promotes the proposal and implementation of air pollutant emissions reduction strategies.

Volatile organic compounds emission inventory of organic chemical raw material industry

The composition, distribution, photochemical activity, and emission profiles of 106 VOCs derived from the organic chemical raw material industry in Shanghai were investigated. Samples collected from eight organic chemical raw material factories that correspond to four industrial subclasses were analyzed via gas chromatography mass spectrometry (GC-MS) and qualitative and semi-quantitative analysis method. The distribution of the VOC components and the typical species corresponding to the different factories showed strong correlation with their raw materials as well as their products. The majority of the VOC components of the organic chemical raw material industry were found to be alkanes and oxygenated VOCs (OVOCs), and their percentage concentrations varied in the range 32.9–99.8%. Pentane, acetone, isopropanol, 1,4-dioxane, and n-hexane were identified as the five most frequently detected VOCs in the samples. Furthermore, in terms of photochemical activity, ozone formation potential (OFP) performed a similar pattern as VOCs results; the average source reactivity (SR) value was 1.70 g/g, which was at the medium-activity stage, indicating that alkenes and alcohols deserve more attention. Additionally, apart from the 106 frequently encountered VOCs, 31 less common VOCs were also detected. The quantitative and semi-quantitative analytical method used herein offered the possibility to detect non-conventional VOCs under common laboratory conditions. This enhanced analytical method demonstrated tremendous potential in improving VOCs monitoring techniques, and our findings showed significance with respect to refining the VOCs source profiles of the organic chemical raw material industry; this makes up for the absence of this information in related fields.

Characterization of ambient volatile organic compounds, source apportionment, and the ozone–NO<sub>x</sub>–VOC sensitivities in a heavily polluted megacity of central China: effect of sporting events and emission reductions

Abstract. The implementation of strict emission control during the 11th National Minority Games (NMG) in September 2019 provided a valuable opportunity to assess the impact of such emission controls on the characteristics of VOCs and other air pollutants. Here, we investigated the characteristics of VOCs and the O3–NOx–VOC sensitivity comprehensively in Zhengzhou before, during, and after the NMG by delivering field measurements combined with WRF-CMAQ (Weather Research and Forecasting Community Multiscale Air Quality) model simulations. The average mixing ratios of VOCs during the control periods were 121 ± 55 µg m−3 and decreased by about 19 % and 11 % before and after emission reduction. The ozone precursors (NOx) also decreased significantly during the control period; however, the ozone pollution was severe during the entire observation period. Positive matrix factorization analysis indicated seven major sources of ambient VOCs, including coal combustion, biomass burning, vehicle exhausts, industrial processes, biogenic emissions, solvent utilization, and liquefied petroleum gas (LPG). The results show that the major source emissions, such as coal combustion and solvent utilization, were significantly reduced during the control period. As for ozone formation potential (OFP), the value during the control period was 183 ± 115 µg m−3, which was 0.23 and 0.17 times lower than before and after the control period, respectively. Solvent utilization and combustion controls were the most important measures taken to reduce OFP during the NMG period. Control policies can effectively reduce carcinogenic risk. However, non-cancer risks of ambient VOC exposures were all exceeding the safe level (hazard quotient = 1) during the sampling periods, and emphasis on the reduction of acrolein emissions was needed. In addition, the WRF-CMAQ model simulation indicated that O3 formation was controlled by VOCs in Zhengzhou. The results of the Empirical Kinetic Modeling Approach showed that the NOx reduction in Zhengzhou might lead to higher ozone pollution. It is suggested that reduction ratios of the precursors (VOCs : NOx) should be more than 2, which can effectively alleviate ozone pollution.

Analysis of the photochemical characteristics and sensitivity of ozone pollution in Xi’an

<p indent="0mm">The Fenwei Plain is an important agricultural production base and transportation hub in China with a residential population of over 55 million. With rapid industrialization and urbanization, this area has experienced serious photochemical pollution in the summer season. In this study, a field campaign was conducted in summer 2019 with measurements of ozone and photochemical precursors in Xi’an, a megacity in the Fenwei Plain. An explicit case was performed to explore O₃-NO_{<italic>x</italic>}-VOCs sensitivity and the local ozone budget using an observation-based model. Results revealed that precursors significantly promoted ozone production. The positive matrix factorization (PMF) model combined with the relative incremental reactivity (RIR) method was applied to identify the key VOC sources that affect ozone formation. An ozone pollution episode lasting <sc>11 d</sc> was selected and divided into three periods: Initial (July 8–11), polluted (July 12–15), and sweep (July 16–18) periods. It was found that strong solar radiation intensity, high temperature, low relative humidity, and low pressure prevailed during the polluted period, which favored ozone production. The maximum O₃ concentrations at the upwind CB site and urban DHS site were found to be 125 ppbv during the polluted period, whereas at the QL site, the maximum O₃ concentrations were much lower (98 ppbv). The maximum local ozone production rate <sc>(<italic>P</italic>(O_{<italic>x</italic>}))</sc> of the three sites during the polluted period was significantly higher than that in the initial and sweep periods. The <italic>P</italic>(O_{<italic>x</italic>}) was 17.7, 33.9, and 14.9 ppbv/h for the CB, DHS, and QL sites, respectively. The <italic>in situ</italic> O_{<italic>x</italic>}<italic> </italic>budget demonstrated that ozone pollution at the CB and DHS sites was mainly attributed to local photochemical production, whereas the regional transportation effect could not be ignored at the QL site. The O₃-NO_{<italic>x</italic>}-VOCs sensitivity analysis revealed that ozone production regimes were transitional, VOCs-limited, and NO_{<italic>x</italic>}-limited at the CB, DHS, and QL sites, respectively, and the regimes stayed unchanged for all the three sites during the entire ozone pollution episode. However, during the initial period at the DHS site, NO_{<italic>x</italic>} reduction led to a negative effect on ozone control. The ozone formation regime obtained from the emission rate box model was consistent with that of the RIR method. From the proportion of grouped VOCs, the alkane and OVOCs were the dominant species in the mixing ratio (78%–86%), whereas the contribution of aromatics to OFP (16%–24%) was second only to that of OVOCs. Finally, by combining the PMF model and RIR method, ozone production was found to be more sensitive to precursors reduction in the initial period than in the polluted period at the three sites, which indicated that pollutants control measures for ozone pollution mitigation will be more effective in the initial than in polluted periods. Therefore, during an ozone pollution episode, the time to take action for ozone pollution control is not during the polluted period when the ozone concentrations peak, but should be brought forward, when controlling the concentration of precursors has the highest efficiency in reducing ozone production.

The characteristics and source analysis of VOCs emissions at roadside: Assess the impact of ethanol-gasoline implementation

To research the effect of ethanol-gasoline on the VOCs emission from vehicles, two long-term roadside experiments were carried out to obtain the characteristics of VOCs emissions from vehicles at TEDA road in Tianjin. The Positive Matrix Factorization (PMF) source analysis model is used to analyze the VOCs at roadside and assess the impact of ethanol-gasoline implementation. The results show that the average VOCs concentration in the roadside environment was 45.67 ± 34.60 μg/m3 in the 2019 experiment. Alkanes, alkenes, halogenated hydrocarbons, alkynes, aromatic hydrocarbons and oxygen volatile organic compounds (OVOCs) accounted for 63.18%, 13.24%, 9.04%, 6.03%, 5.35% and 3.16%, respectively. Compared with the experiment in 2018, the concentration of m/p-xylene and benzene in the roadside environment showed a significant decrease. Five VOCs sources were identified, including gasoline vehicle exhaust emissions (27.46%), diesel vehicle exhaust emissions (23.70%), evaporative emission (22.67%), LPG/CNG vehicle emission (13.86%) and solvent usage (12.30%). The PMF analysis results of 2018 and 2019 showed that the contribution of gasoline vehicle exhaust emissions decreased by 8%, but the contribution rate of evaporative emissions increased by 6%. The implementation of ethanol-gasoline can reduce VOCs emissions from vehicle exhaust, however, the evaporative emissions of VOCs will increase. Evaporative emission from vehicles should be strictly controlled in the future.

Stationary monitoring and source apportionment of VOCs in a chemical industrial park by combining rapid direct-inlet MSs with a GC-FID/MS

Fast and comprehensive monitoring of VOCs, required for air quality management in large-scale chemical industrial parks in China, cannot be accomplished by stationary measurements using conventional GC-FID or GC–MS alone due to their low temporal resolutions and limited detectable ranges. Novel direct-inlet mass spectrometry (DI-MS) has been widely applied for real-time monitoring of VOCs. To verify its applicability in industrial settings, high mass-resolution proton-transfer-reaction time-of-flight MS (HMR-PTR-TOFMS), single-photon ionization time-of-flight MS (SPI-TOFMS), together with online GC-FID/MS were simultaneously deployed at the boundary of one of the largest chemical industrial parks in eastern China. Aromatics, acetonitrile, acetic acid, ethyl acetate, aliphatic hydrocarbons, 1,2-dichloroethane, and acetone were detected as the main pollutants. These three instruments detected 12 common species, among which ethyl acetate, toluene, C8-aromatics, and methyl ethyl ketone showed similar time series and levels. Acetone, benzene, chlorobenzene, styrene, and C9-aromatics showed only similar time series. The HMR-PTR-TOFMS uniquely detected 14 species, mainly oxidized VOCs, nitriles, and amines, which greatly helps acknowledge the pollutants in the chemical industrial area. Positive matrix factorization, using the HMR-PTR-TOFMS and GC-FID/MS datasets, was used to identify eight sources. Four of the identified sources were mainly detected by the HMR-PTR-TOFMS, with pollutants mainly comprised of nitriles, amines, carbonyls, and organic acids, most of which were hazardous and/or odorous. These four sources accounted for 41.5% and 33.2% of the total VOCs and ozone formation potential, respectively. The complementary nature of GC-FID/MS and HMR-PTR-TOFMS in VOC source apportionment in industrial settings is of great practical use for advanced VOCs abatement. Thus, the high mass resolution DI-MSs are suggested to be a supplementary measurement for fence-line monitoring. Although with a relatively short period attempt, this study has wide implications for the fence-line stationary observational modes and source apportion methods combining with traditional observations.

Indoor air quality of 5,000 households and its determinants. Part A: Particulate matter (PM2.5 and PM10–2.5) concentrations in the Japan Environment and Children's Study

Exposure to particulate matter (PM) is one of the important risk factors for morbidity and mortality. Although PM concentrations have been assessed using air quality monitoring stations or modelling, few studies have measured indoor PM in large-scale birth cohorts. The Japan Environment and Children's Study (JECS) measured indoor and outdoor air quality in approximately 5000 households when the participating children were aged 1.5 and 3 years. PM was collected using portable pumps for 7 days (total of 24 h), inside and outside each home. Prediction models for indoor PM concentrations were built using data collected at age 1.5 years and post-validated against data collected at age 3 years. Median indoor/outdoor PM2.5 and PM10–2.5 concentrations at age 1.5 years [3 years] were 12.9/12.7 [12.5/11.3] μg/m3 and 5.0/6.3 [5.1/6.1] μg/m3, respectively. Random forest regression analysis found that the major predictors of indoor PM2.5 were indoor PM10–2.5, outdoor PM2.5, indoor smoking, observable smoke and indoor/outdoor temperature. Indoor PM2.5, outdoor PM10–2.5, indoor humidity and opening room windows were important predictors of indoor PM10–2.5 concentrations. Indoor benzene, acetaldehyde, ozone and nitrogen dioxide concentrations were also found to predict indoor PM2.5 and PM10–2.5 concentrations, possibly due to the formation of secondary organic aerosols. These findings demonstrate the importance of reducing outdoor PM concentrations, avoiding indoor smoking, using air cleaner in applicable and diminishing sources of VOCs that could form secondary organic aerosols, and the resulting models can be used to predict indoor PM concentrations for the rest of the JECS cohort.

Estimation of Contribution by Pollutant Source of VOCs in Industrial Complexes of Gwangju Using Receptor Model (PMF)

Estimation of Contribution by Pollutant Source of VOCs in Industrial Complexes of Gwangju Using Receptor Model (PMF)

Spatiotemporal variation, sources, and secondary transformation potential of volatile organic compounds in Xi'an, China

Abstract. As critical precursors of ozone (O3) and secondary organic aerosols, volatile organic compounds (VOCs) play a vital role in air quality, human health, and climate change. In this study, a campaign of comprehensive field observations and VOC grid sampling was conducted in Xi'an, China, from 20 June to 20 July 2019 to identify the spatiotemporal concentration levels, sources, and secondary transformation potential of VOCs. During the observation period, the average VOC concentrations at the Chanba (CB), Di Huan Suo (DHS), Qinling (QL), and gridded sampling sites were 27.8 ± 8.9, 33.8 ± 10.5, 15.5 ± 5.8, and 29.1 ± 8.4 ppb, respectively. Vehicle exhaust was the primary source of VOC emissions in Xi'an, and the contributions of vehicle exhaust to VOCs at the CB, DHS, and QL sites were 41.3 %, 30.6 %, and 23.6 %–41.4 %, respectively. While industrial emissions were the second-largest source of VOCs in urban areas, contributions from aging sources were high in rural areas. High potential source contribution function values primarily appeared in eastern and southern Xi'an near the sampling site, which indicates that Xi'an exhibits a strong local VOC source. Moreover, alkenes, aromatics, and oxygenated VOCs played a dominant role in secondary transformation, which is a major concern in reducing O3 pollution in Xi'an.

Atmospheric VOC measurements at a High Arctic site: characteristics and source apportionment

Abstract. There are few long-term datasets of volatile organic compounds (VOCs) in the High Arctic. Furthermore, knowledge about their source regions remains lacking. To address this matter, we report a multiseason dataset of highly time-resolved VOC measurements in the High Arctic from April to October 2018. We have utilized a combination of measurement and modeling techniques to characterize the mixing ratios, temporal patterns, and sources of VOCs at the Villum Research Station at Station Nord in northeastern Greenland. Atmospheric VOCs were measured using proton-transfer-reaction time-of-flight mass spectrometry. Ten ions were selected for source apportionment with the positive matrix factorization (PMF) receptor model. A four-factor solution to the PMF model was deemed optimal. The factors identified were biomass burning, marine cryosphere, background, and Arctic haze. The biomass burning factor described the variation of acetonitrile and benzene and peaked during August and September. The marine cryosphere factor was comprised of carboxylic acids (formic, acetic, and C3H6O2) as well as dimethyl sulfide (DMS). This factor displayed peak contributions during periods of snow and sea ice melt. A potential source contribution function (PSCF) showed that the source regions for this factor were the coasts around southeastern and northeastern Greenland. The background factor was temporally ubiquitous, with a slight decrease in the summer. This factor was not driven by any individual chemical species. The Arctic haze factor was dominated by benzene with contributions from oxygenated VOCs. This factor exhibited a maximum in the spring and minima during the summer and autumn. This temporal pattern and species profile are indicative of anthropogenic sources in the midlatitudes. This study provides seasonal characteristics and sources of VOCs and can help elucidate the processes affecting the atmospheric chemistry and biogeochemical feedback mechanisms in the High Arctic.

General discussion: Aerosol formation and growth; VOC sources and secondary organic aerosols.

General discussion: Aerosol formation and growth; VOC sources and secondary organic aerosols.

RESILIENT: A robust statistical method for estimating multiple VOC sources from limited field measurements

Air pollution due to haphazard industrialization has become a major concern in developing countries. Yet, enforcement of related norms remains problematic because violators cannot easily be pinpointed among closely situated industrial units. Accordingly, it has become imperative to equip regulatory authorities with an economical yet accurate tool that quickly locates emission sources and estimates emission rates. Against this backdrop, we propose RESILIENT, a method for Robust Estimation of Source Information from LImited field measuremENTs, which exhibits significant statistical robustness and accuracy even when the data are collected using a low-cost error-prone sensor. In our field experiment, where ground truth was unavailable, the sources estimated to be inactive based on the complete set of measurements were found inactive (up to three decimal places of accuracy) at least 72% of the time even when estimated using just 54% of random measurements. In that setting, rate estimates of active sources were also found to be statistically robust. For direct validation of RESILIENT, we considered a separate public dataset involving 10 tracer experiments, and obtained a significant correlation coefficient of 0.89 between estimated and recorded emission rates, and that of 0.99 between predicted and measured concentration levels at sensor locations.

Process-based VOCs source profiles and contributions to ozone formation and carcinogenic risk in a typical chemical synthesis pharmaceutical industry in China

The chemical synthesis pharmaceutical industry plays an important role in VOCs emissions from industrial sources, which has caused increasing concern. In this study, the process-based pollution characteristics of VOCs from the chemical synthesis pharmaceutical industry were investigated in the Yangtze River Delta, China. A total of 16 samples were collected from 12 process units (including 5 production lines and 2 postprocessing units) and 2 factory boundary sites. 116 VOCs species were analyzed and sorted into 6 classes, including alkanes, alkenes, acetylene, aromatics, halocarbons and oxygenated VOCs (OVOCs). The concentration of stack VOCs was 3.37 × 104 μg·m−3, while the concentration of fugitive VOCs from other process units ranged from 827 μg·m−3 to 2.11 × 104 μg·m−3. Aromatics, halocarbons and OVOCs accounted for a relatively high proportion in all process units. Process-based source profiles of each process unit were compiled. Generally, toluene, dichloromethane, ethanol, methanol and acetone were the most abundant species in all process units. Furthermore, the process-based ozone formation potentials (OFPs) and carcinogenic risk potentials (CRPs) were calculated, suggesting that toluene, methanol, ethanol and m/p-xylene should be preferentially controlled to reduce the OFPs, while acetaldehyde and chloroform were the priority control species to reduce the CRPs. Further discussion showed that ambient VOCs pollution at the factory boundary was affected by both stack and fugitive sources from the production process. The source profiles built in this study are necessary addition to the current profiles and are a good reference to study VOCs emission characteristics from the perspective of the process procedure. The results obtained from this work provide a guidance for effective VOCs abatement strategies and further lay a foundation for related research on VOCs in the chemical synthesis pharmaceutical industry.

A high-resolution spatial and temporal on-road vehicle emission inventory in an Iranian metropolitan area, Isfahan, based on detailed hourly traffic data

The present study is primarily aimed to establish a detailed exhaustive emission inventory of urban motor vehicles in a medium-sized city, i.e. Isfahan. The International Vehicle Emission (IVE) model was utilized to estimate the motor vehicle Emission Factors (EFs) in different areas of Isfahan. IVE was adjusted using the results obtained by on-board real-world EF measurements. A high resolution 1 km × 1 km vehicle emission inventory for the year 2018 was then developed in a bottom-up approach. The method was employed based on the influencing factors such as the collected hourly-data on road network, traffic flow, vehicle driving cycles, and the vehicle population in Isfahan. Moreover, the variations of EFs with vehicle speed were investigated for different vehicle categories to assess the emission rates through Isfahan transportation fleet. The results showed that EFs of all pollutants emitted from vehicle exhausts usually decrease with vehicle speed. Also, gasoline vehicles have larger CO and VOCs EFs than the others, whereas vehicles fueled by diesel have the largest NOx, SOx, and PM10 EFs. The established emission inventory revealed that the annual amount of CO, VOCs, NOx, SOx, and PM10 emitted from Isfahan on-road mobile sources in 2018 are 267.6, 12.6, 20.3, 0.3, and 2.3 kt, respectively. The gasoline vehicles including cars and motorcycles were the main sources of CO, VOCs, and SOx, whereas the heavy-duty vehicles and buses equipped with diesel engines were the main sources of NOx and PM10. The hourly variations of EFs ensure an acceptable consistency with the hourly variation of the traffic flow at different areas. Moreover, the high-resolution spatial distribution of vehicle emission inventory represented that emissions were concentrated on the downtown, esp. on underdeveloped historical area of the city, where the most of the governmental and administrative departments are concentrated.

Source apportionment of hourly-resolved ambient volatile organic compounds: Influence of temporal resolution

High temporal-resolution VOC concentration data can provide detailed and important temporal variations of VOC species and emission sources, which is not possible when using coarse temporal-resolution data. In this study, we utilized the positive matrix factorization (PMF) model to conduct source apportionment of hourly concentrations of nineteen VOC species and CO measured at the Mong Kok air quality monitoring station, operated by the Hong Kong Environmental Protection Department, from January 2013 to December 2014. The PMF analysis of the hourly dataset (PMF_Hourly) identified five sources, including liquefied petroleum gas (LPG) (contribution of 45%), gasoline exhaust (21%), combustion (20%), biogenic emission (9%), and paint solvents (6%). The diurnal patterns of VOC emissions from identified sources are likely to be affected by the strength of emissions, variation of the planetary boundary layer height, and photochemical reactions. In addition, the PMF analyses of hourly and 24-hour averaged data of the hourly-resolved data (PMF_Hourly and PMF_Daily) were generally comparable, but the time series of VOC emissions from PMF_Hourly could not be well captured by PMF_Daily for two local VOC sources of gasoline exhaust and LPG. This study highlights the benefit of high temporal-resolution measurement data in apportioning VOC sources, hence providing critical information on VOC emission sources (e.g., diurnal variations) for controlling VOC emissions effectively.

Source-resolved attribution of ground-level ozone formation potential from VOC emissions in Metropolitan Vancouver, BC

The common regulatory approach for managing ground-level ozone (O3) formation is based upon reducing the emission of total VOC in VOC limited regions, and the emission of NOx in NOx limited regions. However, the characteristic VOC species emitted from different sources are of different ozone formation potentials (OFP). Without an in-depth understanding of the relative OFP contributions from specific sources, the effectiveness of the existing approach for controlling ground-level O3 at the regional scale is limited. This study collected and analyzed five years (2012–2016) of monitoring data for 56 most photochemically reactive VOC species at Port Moody, an industrial city in Metro Vancouver, Canada that has experienced elevated O3 levels in its ambience. Source-specific contributions to OFP were quantified for major VOC emitters to deliberate the underlying causes of elevated O3 recently observed in this populated region.Six sources were identified using the positive matrix factorization (PMF) model, consisting of fuel production and combustion, fuel evaporation, vehicle exhaust, industrial coatings/solvents, petrochemical source, and other industrial emission. Although the top three contributors to total VOCs are fuel production and combustion (34.5%), fuel evaporation (21.4%), and vehicle exhaust (20.6%), the top three contributors to OFP are fuel production and combustion (27.1%), vehicle exhaust (23.7%), and industrial coatings/solvents (17.2%). Additionally, potential source contribution function (PSCF) analysis was conducted to generate the geographical distribution of VOC and OFP sources in different seasons. The results revealed that, in the Metro Vancouver area, the OFP hotspots have been significantly different from the VOC emission hotspots. In general, regional sources, especially those located in the northeastern direction of Metro Vancouver, have greater influence on the VOCs levels. However, OFP has been predominantly affected by transportation and industrial sources at the local scale. Therefore, to formulate effective strategies for reducing ground-level O3, the seasonal and spatial variations of major OFP sources should be assessed by the regulatory authorities.

An investigation into the role of VOCs in SOA and ozone production in Beijing, China

In recent years, PM2.5 and O3 pollutions are prevalent in the atmosphere in Beijing. The study on pollution characteristics of VOC, which are important precursors of O3 and secondary organic aerosols (SOA) contributing PM2.5, is of great significance for providing a reference to guide its reduction policy formulation. Herein, the seasonal variation of atmospheric VOCs and meteorological conditions at the sampling frequency of 1 time per hour were continuously measured from March 2016 to January 2017 in Beijing. Using the collected data combined with multiple models, the role of VOCs in SOA and O3 production was investigated. Alkanes were the most abundant species, contributing 54.1–64.7% of the total VOC concentration for four seasons, followed by aromatics, alkenes and acetylene. The SOA potential (SOAP) was highest in winter at 2885.1 μg m−3, followed by autumn, spring and summer. Aromatics were the main contributors to SOAP, accounting for ~98.2% of the total SOAP during the entire observation period. The empirical kinetic modeling approach results showed that O3 production featured the VOC-limited regime in Beijing. Alkenes and aromatics were major contributors to O3 formation potential (OFP), accounting for 33.1–45.6% and 27.2–45.2%, respectively, particularly ethylene and m,p-xylene. Positive matrix factorization results indicated that motor vehicle exhaust was still the largest local source of VOCs, but its proportion was considerably reduced. The potential source contribution function results revealed that regional transport sources of VOC pollution in Beijing mainly came from the northwest and southern areas. Thus, to control PM2.5 and O3 pollution in Beijing, the restriction of alkenes and aromatics emission, accompanied by regional cooperation combined with local control, is essential.

Discrimination and geo-spatial mapping of atmospheric VOC sources using full scan direct mass spectral data collected from a moving vehicle.

Volatile and semi-volatile organic compounds (S/VOCs) are ubiquitous in the environment, come from a wide variety of anthropogenic and biogenic sources, and are important determinants of environmental and human health due to their impacts on air quality. They can be continuously measured by direct mass spectrometry techniques without chromatographic separation by membrane introduction mass spectrometry (MIMS) and proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). We report the operation of these instruments in a moving vehicle, producing full scan mass spectral data to fingerprint ambient S/VOC mixtures with high temporal and spatial resolution. We describe two field campaigns in which chemometric techniques are applied to the full scan MIMS and PTR-ToF-MS data collected with a mobile mass spectrometry lab. Principal Component Analysis (PCA) has been successfully employed in a supervised analysis to discriminate VOC samples collected near known VOC sources including internal combustion engines, sawmill operations, composting facilities, and pulp mills. A Gaussian mixture model and a density-based spatial clustering of application with noise (DBSCAN) algorithm have been used to identify sample clusters within the full time series dataset collected and we present geospatial maps to visualize the distribution of VOC sources measured by PTR-ToF-MS.

VOCs evaporative emissions from vehicles in China: Species characteristics of different emission processes

Vehicle evaporation is an essential source of VOCs in cities but is not well understood in China. Reported emission factors from previous studies are not enough for understanding the atmospheric chemical process of vehicular evaporative VOCs. In this work, a serious of detailed VOCs speciation profiles are developed based on test processes and emission processes. A mass balance method was used to divide different emission processes during diurnal tests. The results show that headspace vapor of gasoline cannot represent the real-world vehicle evaporation because of the significant differences in VOCs speciation profiles, especially for aromatics. To further distinguish emissions from evaporation and exhaust, only the ratios of MTBE/benzene and MTBE/toluene can serve as indicators when considering species from all evaporative processes. Besides, emissions from different sources change significantly with the seasons. To solve these problems, we developed a monthly comprehensive evaporation speciation profile. The individual profiles at the emission processes are weighted by the emission of the in-use vehicle fleet in Beijing to derive the comprehensive speciation profile of evaporative VOCs. Ozone formation potential (OFP) and secondary organic aerosol potential (SOAP) were used to evaluate the environmental impact. For SOAP, 100 ​g evaporative emissions are equal to 6.05–12.71 ​g toluene in different months, much higher than that given using headspace vapors, especially in winter (7.2 times higher in December). These findings would improve our understanding of the evaporative VOCs emissions in China and their environmental impacts (e.g., O3 and SOA formation).

Estimation of Anthropogenic VOC Source Area around Tokyo Bay: Results from the VOC Concentration Changes in Relation to Wind Direction

Estimation of Anthropogenic VOC Source Area around Tokyo Bay: Results from the VOC Concentration Changes in Relation to Wind Direction