Chemical composition of major VOC emission sources in the Seoul atmosphere

Ambient volatile organic compounds in the Seoul metropolitan area of South Korea: Chemical reactivity, risks and source apportionment

The chemical reactivity, contribution of emission sources, and risk assessment of volatile organic compounds (VOCs) in the atmosphere of the Seoul metropolitan area (SMA) were analyzed. Datasets collected from 6 photochemical assessment monitoring stations (PAMS) of SMA from 2018 to 2021 were used. Alkenes and aromatics contributed significantly to ozone formation relative to the emission concentrations, and aromatics accounted for most of the secondary organic aerosols (SOA) formation in the SMA. The contributions of ozone and SOA formation were found to be notably higher at measurement stations in residential areas such as Guwol (GW) and Sosabon (SS) compared to other measurement stations. From the results of an emission source analysis, it was confirmed that anthropogenic sources such as combustion sources, vehicle exhaust, fuel evaporation, and solvent use had a significant effect at all measurement stations. Assessing the health risk, non-carcinogenic compounds were at acceptable level at all measurement stations. On the other hand, carcinogenic compounds were approaching risk level (10-4), thereby demanding immediate attention. The level of exposure to carcinogenic compounds increased by age group, and male was more vulnerable than female. It was found that SS had the highest level of exposure to carcinogens in the atmosphere of the population ages 60 or older. The health threat of the SMA population is expected due to direct exposure from inhalation of ambient toxic compounds and indirect exposure from ozone and PM2.5 formations through oxidation of VOCs. This study emphasizes the importance of addressing specific emission sources within the metropolitan area and developing comprehensive regional strategies to mitigate VOCs.

Source apportionment of consumed volatile organic compounds in the atmosphere

Conventional source apportionments of ambient volatile organic compounds (VOCs) have been based on observed and initial concentrations after photochemical correction. However, these results have not been related to ozone (O3) and secondary organic aerosol (SOA) formation. Thus, the apportioned contributions could not effectively support secondary pollution control development. Source apportionment of the VOCs consumed in forming O3 and SOA is needed. A consumed VOC source apportionment approach was developed and applied to hourly speciated VOCs data from June to August 2022 measured in Laoshan, Qingdao. Biogenic emissions (56.3%), vehicle emissions (17.2%), and gasoline evaporation (9.37%) were the main sources of consumed VOCs. High consumed VOCs from biogenic emissions mainly occurred during transport from parks to the southwest and northwest of study site. During the O3 pollution period, biogenic emissions (46.3%), vehicle emissions (24.2%), and gasoline evaporation (14.3%) provided the largest contributions to the consumed VOCs. However, biogenic emissions contribution increased to 57.1% during the non-O3 pollution period, and vehicle emissions and gasoline evaporation decreased to 16.5% and 9.01%, respectively. Biogenic emissions and the mixed source of combustion sources and solvent use contributed the most to O3 and SOA formation potentials during the O3 pollution period, respectively.

Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics

The oxidation of aromatics contributes significantly to the formation of atmospheric aerosol. Using toluene as an example, we demonstrate the existence of a molecular rearrangement channel in the oxidation mechanism. Based on both flow reactor experiments and quantum chemical calculations, we show that the bicyclic peroxy radicals (BPRs) formed in OH-initiated aromatic oxidation are much less stable than previously thought, and in the case of the toluene derived ipso-BPRs, lead to aerosol-forming low-volatility products with up to 9 oxygen atoms on sub-second timescales. Similar results are predicted for ipso-BPRs formed from many other aromatic compounds. This reaction class is likely a key route for atmospheric aerosol formation, and including the molecular rearrangement of BPRs may be vital for accurate chemical modeling of the atmosphere.

VOC and trace gas measurements and ozone chemistry over the Chesapeake Bay during OWLETS-2, 2018

The Ozone Water-Land Environmental Transition Study, 2018 (OWLETS-2) measured total non-methane hydrocarbons (TNMHC) and EPA PAMS Volatile Organic Compounds (VOCs) on an island site in the northern Chesapeake Bay 2.1 and 3.4 times greater in concentration, respectively, than simultaneous measurements at a land site just 13 km away across the land-water interface. Many PAMS VOCs had larger concentrations at the island site despite lower NEI emissions over the water, but most of the difference comprised species generally consistent with gasoline vapor or exhaust. Sharp chemical differences were observed between the island and mainland and the immediate air ~300 m above the water surface observed by airplane. Ozone formation potential over land was driven by propene and isoprene but toluene and hexane were dominant over the water with little isoprene observed. VOC concentrations over the water were noted to increase diurnally with an inverse pattern to land resulting in increasing NO_x sensitivity over the water. Total reactive nitrogen was lower over the water than the nearby land site, but reservoir compounds (NO_z) were greater. Ozone production rates were generally slow (~5 ppb hr^-1) both at the surface and aloft over the water, even during periods of high ozone (>70 ppbv) at the water surface. However, specific events showed rapid ozone production >40 ppb hr^-1 at the water's surface during situations with high VOCs and sufficient NO_x. VOC and photochemistry patterns at the island site were driven by marine sources south of the island, implicating marine traffic, and indicate ozone abatement strategies over land may not be similarly applicable to ozone over the water.Implications: Measured chemical properties and patterns driven primarily by marine traffic sources over water during ozone conducive conditions were starkly different to immediately adjacent land sites, implying ozone abatement strategies over land may not be similarly applicable to ozone over the water.

Pollution mechanisms and photochemical effects of atmospheric HCHO in a coastal city of southeast China

Formaldehyde (HCHO) is a vital reactive carbonyl compound, which plays an important role in the photochemical process and atmospheric oxidation capacity. However, the current studies on the quantification of HCHO impacts on atmospheric photochemistry in southeast coastal areas of China with an obvious upward trend of ozone remain scarce and unclear, thus limiting the full understanding of formation mechanism and control strategy of photochemical pollution. Here, systematic field campaigns were conducted at a typical coastal urban site with good air quality to reveal HCHO mechanism and effects on O₃ pollution mechanism during spring and autumn, when photochemical pollution events still frequently appeared. Positive Matrix Factorization model results showed that secondary photochemical formation made the largest contributions to HCHO (69 %) in this study. Based on the photochemical model, the HCHO loss rates in autumn were significantly higher than those in spring (P < 0.05), indicating that strong photochemical conditions constrain high HCHO levels in certain situations. HCHO mechanism increased the ROx concentrations by 36 %, and increased net O₃ production rates by 31 %, manifesting that the reduction of HCHO and its precursors' emissions would effectively mitigate O₃ pollution. Therefore, the pollution characteristics and photochemical effects of HCHO provided significant guidance for future photochemical pollution control in relatively clean areas.

Observation-based sources evolution of non-methane hydrocarbons (NMHCs) in a megacity of China

Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China, in contrast to the fact that an increase in emissions of non-methane hydrocarbons (NMHCs) has been reported. This study employed seven years continuous NMHCs measurements and the related activities data of Shanghai, a megacity in China, to explore evolution of emissions and effectiveness of air pollution control measures. The mixing ratio of NMHCs showed no statistical interannual changes, of which their compositions exhibited marked changes. This resulted in a decreasing trend of ozone formation potential by 3.8%/year (p < 0.05, the same below), which should be beneficial to ozone pollution mitigation as its production in Shanghai is in the NMHCs-limited regime. Observed alkanes, aromatics and acetylene changed by +3.7%/year, -5.9%/year and -7.4%/year, respectively, and alkenes showed no apparent trend. NMHCs sources were apportioned by a positive matrix factorization model. Accordingly, vehicular emissions (-5.9%/year) and petrochemical industry emissions (-7.1%/year) decreased significantly, but the decrease slowed down; significant reduction in solvent usage (-9.0%/year) appeared after 2010; however, emissions of natural gas (+12.6%/year) and fuel evaporation (with an increasing fraction) became more important. The inconsistency between observations and inventories was found in interannual trend and speciation as well as source contributions, emphasizing the need for further validation in NMHCs emission inventory. Our study confirms the effectiveness of measures targeting mobile and centralized emissions from industrial sources and reveals a need focusing on fugitive emissions, which provided new insights into future air policies in polluted region.

New Insights for Tracking Global and Local Trends in Exposure to Air Pollutants

Over six million people die prematurely each year from exposure to air pollution. Current air quality metrics insufficiently monitor exposure to air pollutants. This gap hinders the ability of decisionmakers to address the public health impacts of air pollution. To spur new emissions control policies and ensure implemented solutions realize meaningful gains in environmental health, we develop a framework of public-health-focused air quality indicators that quantifies over 200 countries' trends in exposure to particulate matter, ozone, nitrogen oxides, sulfur dioxide, carbon monoxide, and volatile organic compounds. We couple population density to ground-level pollutant concentrations to derive population-weighted exposure metrics that quantify the pollutant levels experienced by the average resident in each country. Our analyses demonstrate that most residents in 171 countries experience pollutant levels exceeding international health guidelines. In addition, we find a negative correlation between temporal trends in ozone and nitrogen oxide concentrations, which─when qualitatively interpreted with a simple atmospheric chemistry box model─can help describe the apparent tradeoff between the mitigation of these two pollutants on local scales. These novel indicators and their applications enable regulators to identify their most critical pollutant exposure trends and allow countries to track the performance of their emission control policies over time.

Refueling emission of volatile organic compounds from China 6 gasoline vehicles

Vehicular refueling emission is a potential source of urban atmospheric volatile organic compounds (VOCs) that is not well understood and controlled. China 6 vehicles have been equipped with the onboard refueling vapor recovery (ORVR) system to cut down refueling emissions, while the emission characteristics and reduction effectiveness are rarely reported. In this study, we conducted laboratory tests to measure the refueling emissions from ten China 6 vehicles and three China 5 vehicles (refueling-emission-uncontrolled, REU) and developed an inventory in a typical middle-sized Chinese city (Langfang) to explore the emission reduction resulted from relevant policies. Compared with headspace vapor and refueling vapor from REU vehicles, the emission profiles for China 6 vehicles are consist of considerably higher proportions of small alkanes and alkenes (C2-C3) and lower proportions of C6-C8 hydrocarbons. Such differences indicate that the headspace vapor profiles are incapable of representing the refueling emission for China 6 vehicles. The market-share-weighting emission factors (EFs) of total hydrocarbons (THCs) and total VOCs for China 6 vehicles are 11.2 mg/L and 6.4 mg/L, respectively, corresponding to control efficiency of approximately 98.8% compared with the REU vehicles. Based on the real-world EFs and the fuel consumption in Langfang, a refueling emission inventory with high spatiotemporal resolution is developed. The total refueling emission of THCs in Langfang is approximately 190.6 tons in 2018 and will likely decline to 25.0 tons in 2035. The implementation of the ORVR will contribute to 90% of the refueling emission reduction in 2035.

Cancer risk assessment for exposure to hazardous volatile organic compounds in Calgary, Canada

Oil and natural gas (O&G) extraction operations emit hazardous volatile organic compounds (VOCs) in quantities that have adverse effects on human health. Our current understanding of the exposure risks associated with upstream O&G exploitations remains limited, and very few quantitative on-site remediation strategies have been proposed. To this end, we assessed the health risks associated with the emission of hazardous VOCs and presented a set of remediation goals for the city of Calgary, which is a major center of the Canadian oil industry. Results from probabilistic risk assessment (PRA) suggested that although VOCs had a negligible impact on chronic non-cancer-associated risk, inhalation-associated cancer risk remained a significant concern. Carbon tetrachloride, benzene, and 1,3-butadiene were the dominant VOCs, representing 88% of the integrated inhalation cancer risk (= 7.8 × 10^-5); background, solid fuel combustion, and O&G extraction were among the primary sources that posed the greatest threat to human health. Results of a Monte Carlo simulation revealed that the probability of developing cancer due to inhalation of hazardous VOCs was ∼13.1% on clean air days and 45.9% on days with significant levels of air pollution. Preliminary remediation goals (PRGs) included reductions of 24.2-65.1% and 11.4-50.9% targeting priority VOCs and their sources, respectively. Taken together, our findings suggest that stringent control of the sources of VOCs, particularly fossil fuel combustion, is an urgent priority. PRA coupled with PRGs provides informative risk assessments and suggests quantitative remediation strategies that can be applied toward improved management of hazardous pollutants.

Modeling VOC adsorption in lab- and industrial-scale fluidized bed adsorbers: Effect of operating parameters and heel build-up

Scale-up and optimization of fluidized beds are challenging due to the difficulty in accounting for the interrelated effect of various phenomena, which are typically described by empirical and/or semi-empirical equations. In this study, a two-phase model was introduced to simulate the adsorption of VOCs on beaded activated carbon (BAC) in a lab-scale fluidized bed adsorber. The model assumes the presence of a bubble phase free from adsorbent particles, and an emulsion phase composed of the adsorbent particles and interstitial gas. The versatility of the proposed model was then evaluated using data from an industrial scale adsorber with different operating conditions, adsorbent properties, and bed geometry. The response of the model to the operating conditions (adsorbent feed rate, air flow rate and initial concentration) showed better agreement with the experimental lab-scale data when the emulsion gas in two-phase model was considered in plug flow than in perfectly-mixed flow (R² = 0.96 compared to 0.91). To simulate the performance of BACs with different service lifetimes (degree of exhaustion as a result of heel developed inside their pores), the main characteristics of the BACs (pore diameter, porosity, and adsorption capacity) were first correlated to their apparent densities. The model could accurately predict the experimental lab-scale VOC concentrations in each stage (R² = 0.92) as well as overall removal efficiencies (R² = 0.99) for BACs ranging from virgin to fully-spent. Finally, the model was used to predict the performance of an industrial-scale fluidized bed adsorber for VOC removal at different operating conditions and apparent densities. Predicted and measured VOC removal efficiencies were in good agreement (R² = 0.94). Although the model was verified for adsorption of VOCs on BAC, the modeling approach presented in this study could be used for describing adsorption in different adsorbate-adsorbent systems in multistage counter-current fluidized bed adsorbers.

Optimization of a volatile organic compound control strategy in an oil industry center in Canada by evaluating ozone and secondary organic aerosol formation potential

Volatile organic compounds (VOCs) play a vital role in the formation of photochemical smog and haze in large urban environments. Previous source apportionment studies have focused on the contribution of different sources to VOC concentration with a view to pinpointing the major culprits for effective emission mitigation. However, different VOC sources may have different ozone (O₃) and secondary organic aerosol (SOA) formation potentials. From a control perspective, it would be more rational to consider the role of individual VOC sources in secondary pollution; therefore, here, we propose a tiered source identification method that considers the formation potentials of O₃ and SOA, which we applied in Calgary, Alberta, a site under the influence of multiple competing VOC sources. The pollution characteristics, secondary pollutant formation potential, and geographical origin of VOC sources were investigated over a five-year period. Seven major sources were identified using the positive matrix factorization (PMF) model, among which vehicle exhausts and solid fuel combustion were the dominant VOC sources responsible for O₃ (60%) and SOA (63%) formation. Combustion of both liquid fuel (gasoline and diesel) and solid fuel (wood and coal) has exceeded the contribution of oil and gas production and become the top contributor to O₃ and aerosol pollution in Calgary. This finding is consistent with the significant reduction (32.2-99.8%) in oil and gas production in Calgary over the period of 2013-2017. The source apportionment results show that the primary VOC source has shifted from conventional oil and gas extraction to a mixture of vehicle exhausts and oil and gas extraction, indicating the effectiveness of emission control measures taken in the energy sectors. Moreover, regionally transported VOCs from combustion sources in southeastern British Columbia have greatly increased the VOC level and secondary pollutant formation in Calgary. To effectively alleviate secondary pollution problems, the performance of joint pollution control measures has been suggested by the governments of both Alberta and British Columbia. These findings reveal that the tiered source identification strategy combining the traditional receptor model with socioeconomic factors, emission inventory, and source region analysis is a robust and promising tool for the interpretation of source apportionment results and optimization of secondary pollution control.

Characteristics of roadside volatile organic compounds in an urban area dominated by gasoline vehicles, a case study in Hanoi

Volatile organic compounds (VOCs) are important air pollution issues because of their potential health effects, and the contribution to ground ozone and secondary particulate matter. In this study, 53 VOC species near nine roads in Hanoi were monitored by sampling and analyzed by GC-FID four times per day on weekdays and in the morning on the weekend, from December 2014 to January 2015. In parallel with VOC sampling, vehicle number was counted, and meteorological conditions were recorded. A large share of motorbikes was found, accounted for 82% of overall for all period, and 88% in rush hours. The average TVOC concentration was 305.1 ppb; while those of BTEX were 12.8/27.4/4.8/15.9/6.0 ppb for benzene/toluene/ethylbenzene/m,p-xylenes/o-xylene, respectively. Isopentane was the most abundant species of VOCs. A significant carcinogenic risk of benzene species was found. Ozone formation potential (OFP) of VOCs was of 1752.7 ppb. Levels of VOC species reflected well the transportation volume. Strong correlations between motorbike number related parameters and ethylbenzene were found. High correlations were also found among ethylbenzene and almost all other VOC species. It implied that the majority of VOCs near road emitted from the same source, which is motorbikes. The calculation using emission factors from COPERT 5 model with conditions of fleets in Hanoi showed that VOCs from motorbikes contributed to more than 90% of the VOC level.

Quantifying source contributions of volatile organic compounds under hydraulic fracking moratorium

Volatile organic compounds (VOCs) are precursors for ozone (O₃) and secondary particulate matter, which contribute to asthma and cardiovascular diseases. With the technology development of hydraulic fracking, the United States experienced a shale gas boom in the last decade while the public raised concerns about the potential health impacts of co-emitted VOCs and other airborne pollutants. National Energy Technology Laboratory conducted stationary trailer-based ambient monitoring to study the sources of VOCs in Maryland, where the state enacted a moratorium on unconventional natural gas extraction. The campaign had two periods, May to August 2014 (summer) and November 2014 to February 2015 (winter). Ethane was the most abundant VOC, averaging 12.3 ppb (SD = 15.7 ppb) in summer and 21.7 ppb (SD = 21.6 ppb) in winter. The seasonal variation of VOCs indicated different source strengths. The sampling region was in the nitrogen oxides (NO_x) limited regime for O₃ production, and the O₃ concentrations were sensitive to VOC/NO_x ratios in the early mornings. We derived a six-factor profile using positive matrix factorization: motor vehicles, industrial, biogenics, coal burning, fugitive and evaporative, and ozone secondary. The fugitive and evaporative factor explained 44.5% of total VOCs, and the motor vehicles factor followed second with 15.5%. Oil and gas activities had a considerable impact on the abundance of VOCs in this region.

Impact of industrial activities on atmospheric volatile organic compounds in Sihwa-Banwol, the largest industrial area in South Korea

The impact of industrial activities on atmospheric volatile organic compounds (VOCs) in the Sihwa-Banwol complexes, i.e., the largest industrial area in Korea, was investigated. More than 60 VOCs were determined from 850 samples collected from four sites in and around the complexes through a 2-year monitoring campaign from 2005 to 2007. The VOCs of particular concern found in the area were benzene, toluene, ethylbenzene, xylenes, trichloroethylene, and formaldehyde, given their toxicity, concentration, and detection frequency. Toluene was the most abundant one. The VOC concentration rankings were consistent with their emission rankings. Most VOCs had higher concentrations at the industrial sites than at residential sites, indicating a significant impact of industrial emissions. The ambient levels of benzene and formaldehyde were additionally affected by vehicular emissions and secondary formation, respectively. Overall, the VOC levels increased in winter and at night, because of the local weather conditions. In contrast, the formaldehyde concentration increased in summer, owing to its secondary formation in the atmosphere. The ambient VOC levels in Sihwa-Banwol were higher than those in other parts of Korea. Additionally, the cumulative cancer risks posed by the toxic VOCs exceeded a tolerable risk level of 1 × 10^-4 in not only the industrial areas but also the residential areas. The sum of the non-cancer risks in both areas significantly exceeded the threshold criterion of 1. The large amounts of aromatic compounds emitted from the industrial complexes are believed to play a crucial role in the elevated levels of surface ozone in the Seoul metropolitan area during the summer season. Therefore, comprehensive measures for controlling the VOC emissions in the Sihwa-Banwol area need to be prioritized to reduce the health risks for residents of not only this area but also the capital Seoul and its surrounding areas.

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 NO_x in NO_x 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.

Spatiotemporal Variations and Health Implications of Hazardous Air Pollutants in Ulsan, a Multi-Industrial City in Korea

We measured a wide range of hazardous air pollutants (HAPs) simultaneously at five sites over four seasons in 2009–2010 in Ulsan, the largest industrial city in Korea. Target analytes included volatile organic compounds (VOCs), carbonyls, polycyclic aromatic hydrocarbons (PAHs), phthalates, and heavy metals (HMs). The objectives of this study were to evaluate the occurrence and spatiotemporal distributions of HAPs, and to identify important HAPs based on health risk assessment. Industrial emissions affected ambient levels of VOCs and HMs, as demonstrated by spatial distribution analysis. However, concentrations of PAHs and phthalates were relatively uniform at all sites. VOCs and HMs exhibited little seasonal variation, while formaldehyde increased in the summer due to its secondary formation. PAHs exhibited notable seasonal variation; higher in cold seasons and lower in warm seasons. Cumulative cancer risks imposed by 35 HAPs were 4.7 × 10−4 and 1.7 × 10−4 in industrial and residential areas, respectively. The top five major cancer risk drivers appeared to be formaldehyde, benzene, benzo[a]pyrene, As, and Co. The sums of hazard quotients (HQ) derived by 47 HAPs were 10.0 (industrial) and 2.4 (residential). As the individual species, only two HAPs exceeded the HQ of 1, which are As (3.1) and Pb (2.1) in the industrial area. This study demonstrated the importance of a comprehensive monitoring and health risk assessment to prioritize potentially toxic pollutants in the ambient air of a large industrial city.

Understanding the sources and spatiotemporal characteristics of VOCs in the Chengdu Plain, China, through measurement and emission inventory

In order to evaluate the volatile organic compounds (VOCs) pollution characteristics in Chengdu and to identify their sources, ambient air sample collection and measurement were conducted at 28 sampling sites covering all districts/counties of Chengdu from May 2016 to January 2017. Meanwhile, a county-level anthropogenic speciated VOCs emission inventory was established by "bottom-up" method for 2016. Then, a comparison was made between the VOCs emissions, spatial variations, and source structures derived from the measurement and emission inventory. Ambient measurements showed that the annual average mixing ratios of VOCs in Chengdu were 57.54 ppbv (12.36 to 456.04 ppbv), of which mainly dominated by alkanes (38.8%) and OVOCs (22.0%). The ambient VOCs in Chengdu have distinct spatiotemporal characteristics, with a high concentration in January at the middle-northern part of the city and a low concentration in September at the southwestern part. The spatial distribution of VOCs estimated by the emission inventory was in good agreement with ambient measurements. Comparison of individual VOCs emissions indicated that the emissions of non-methane hydrocarbon species agreed within ±100% between the two methods. Both positive matrix factorization (PMF) model results and emission inventory showed that vehicle emissions were the major contributor of anthropogenic VOCs in Chengdu (31% and 37%), followed by solvent utilization (26% and 27%) and industrial processes (23% and 30%). The large discrepancies were found between the relative contribution of combustion sources, and the PMF resolved more contributions (20%) than the emission inventory (6%). Overall, this study demonstrates that measurement results and emission inventory were in a good agreement. However, to improve the reliability of the emission inventory, we suggest significant revision on source profiles of oxygenated volatile organic compounds (OVOCs) and halocarbons, as well as more detailed investigation should be made in terms of energy consumption in household.

Ambient volatile organic compounds (VOCs) in two coastal cities in western Canada: Spatiotemporal variation, source apportionment, and health risk assessment

Ambient volatile organic compounds (VOCs) in urban areas is of great interest due to their important roles in the atmospheric photochemistry as well as their potential adverse effects on public health. Limited information is available on the spatiotemporal variation, sources, and health risks of VOCs in the coastal cities of Canada, where the population density is much higher than inland areas. In this study, we investigated ambient VOCs levels, their potential sources and associated health risks in two coastal cities in Metro Vancouver during 2012-2016. Levels of the total measured VOCs were relatively higher in an industrial region in Port Moody (56.7 μg/m³) than an urban area of Burnaby south (38.0 μg/m³). A clear seasonality was observed for VOCs species with significantly higher levels in winter than in summer except for isoprene. Alkanes were the most dominant compounds at both sites accounting for up to 59.4% of the total measured VOCs, followed by halocarbons, aromatics, and alkenes. Industrial-related emissions (30.5%) and traffic-related emissions (35.8%) were the major sources contributing to ambient VOCs in Port Moody and Burnaby south, respectively, as calculated by the positive matrix factorization (PMF) model. A hybrid health risk assessment strategy using deterministic and stochastic approaches revealed that non-cancer risks of ambient VOCs exposure were all below the safe level of 1 at both cities, while the cumulative cancer risks of toxic VOCs exposure in Port Moody (9.2 × 10^-5) and Burnaby south (7.6 × 10^-5) were significantly higher than the provincial acceptable risk level (1.0 × 10^-5). Surprisingly, the probabilities for cumulative cancer risks of VOCs exceeding the US EPA tolerable risk level (1.0 × 10^-4) were 33.7% and 18.6% in Port Moody and Burnaby south, respectively. From a risk management perspective, greater emphasis on the reduction of emissions of carbon tetrachloride, benzene, and 1,3-butadiene is highly recommended in both cities of Metro Vancouver.

Soil toxicants that potentially affect children's health

Soil pollution is a global phenomenon, and children are uniquely susceptible to the wide range of toxicants that persist in topsoil. Given their increased exposure through mouthing activities, increased body surface area, likelihood of breathing air closer to soil, and immature immune and elimination systems, it is essential to understand the mechanisms of children's exposure and the potential health effects of toxicants found in soil. Here we describe the sources and toxicological profiles of a range of inorganic and organic soil contaminants, including arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), benzene, toluene, ethylbenzene and xylenes, chlorinated dibenzo-p-dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), per and polyfluoroalkyl substances (PFAS), as well as agricultural and domestic sources of pollution. The aim of this article is to increase awareness regarding the risks and health impacts of contaminated soil, and to encourage further research and efforts aimed at mitigating children's exposure.

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).

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VOCs from refueling, hot soak, diurnal, and permeation tests were analyzed.

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Species profiles of the different emission processes were divided from the test process.

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A monthly comprehensive profile of evaporative emission in Beijing was estimated.

Photocatalytic Abatement of Volatile Organic Compounds by TiO2 Nanoparticles Doped with Either Phosphorous or Zirconium

The aim of this work is to study the activity of novel TiO2-based photocatalysts doped with either phosphorus or zirconium under a UV-Vis source. A set of mesoporous catalysts was prepared by the direct synthesis: TiO2_A and TiO2_B (titanium oxide synthesized by two different procedures), P-TiO2 and Zr-TiO2 (binary oxides with either nonmetal or metal into the TiO2 framework). Complementary characterizations (N2 physisorption at 77 K, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, X-ray Photoelectron Spectroscopy (XPS), and (DR)UV-Vis spectroscopy) were used to investigate the physicochemical properties of the prepared catalysts. Then, the photocatalysts were tested for the oxidation of propylene and ethylene under UV-Vis light. As a result, the most promising catalyst for both the propylene and ethylene oxidation reactions was the P-TiO2 (propylene conversion = 27.8% and ethylene conversion = 13%, TOS = 3 h), thus confirming the beneficial effect of P-doping into the TiO2 framework on the photocatalytic activity.

Quantifying Urban Spatial Variations of Anthropogenic VOC Concentrations and Source Contributions with a Mobile Sampling Platform

Volatile organic compounds (VOCs) are important atmospheric constituents because they contribute to formation of ozone and secondary aerosols, and because some VOCs are toxic air pollutants. We measured concentrations of a suite of anthropogenic VOCs during summer and winter at 70 locations representing different microenvironments around Pittsburgh, PA. The sampling sites were classified both by land use (e.g., high versus low traffic) and grouped based on geographic similarity and proximity. There was roughly a factor of two variation in both total VOC and single-ring aromatic VOC concentrations across the site groups. Concentrations were roughly 25% higher in winter than summer. Source apportionment with positive matrix factorization reveals that the major VOC sources are gasoline vehicles, solvent evaporation, diesel vehicles, and two factors attributed to industrial emissions. While we expected to observe significant spatial variability in the source impacts across the sampling domain, we instead found that source impacts were relatively homogeneous.

Source apportionment of VOCs and their impact on air quality and health in the megacity of Seoul

The source apportionment of volatile organic compounds (VOCs) was examined using receptor models (positive matrix factorization and chemical mass balance) and a chemical transport model (CTM). The receptor model-based analysis was performed using the datasets collected from four different sites from the megacity of Seoul during the years 2013-2015. The contributions of VOC emission sources to ozone (O₃) and PM_2.5 concentrations and the subsequent health effects in the study area were also assessed during a photochemically active period (June 2015) using a three-dimensional CTM, Community Multi-scale Air Quality (CMAQ), and the Environmental Benefits Mapping and Analysis Program (BenMAP). The solvent use and the on-road mobile emission sources were found to exert dominant controls on the VOC levels observed in the target city. VOCs transported from regions outside of Seoul accounted for a significant proportion (up to approximately 35%) of ambient VOC levels during the study period. The solvent use accounted for 3.4% of the ambient O₃ concentrations during the day (daily mean of 2.6%) and made insignificant contributions to PM_2.5 (<1%) during the simulation period. Biogenic VOC made insignificant contributions to O₃ (<1%) and a small contribution to PM_2.5 during the day (5.6% with a daily mean of 2.4%). The number of premature deaths attributed indirectly (O₃ and PM_2.5 formations via the oxidation of VOCs) to solvent use is expected to be significant.

Global tropospheric effects of aromatic chemistry with the SAPRC-11 mechanism implemented in GEOS-Chem version 9-02

The Goddard Earth Observing System with chemistry (GEOS-Chem) model has been updated with the Statewide Air Pollution Research Center version 11 (SAPRC-11) aromatics chemical mechanism, with the purpose of evaluating global and regional effects of the most abundant aromatics (benzene, toluene, xylenes) on the chemical species important for tropospheric oxidation capacity. The model evaluation based on surface and aircraft observations indicates good agreement for aromatics and ozone. A comparison between scenarios in GEOS-Chem with simplified aromatic chemistry (as in the standard setup, with no ozone formation from related peroxy radicals or recycling of NOx) and with the SAPRC-11 scheme reveals relatively slight changes in ozone, the hydroxyl radical, and nitrogen oxides on a global mean basis (1 %-4 %), although remarkable regional differences (5 %-20 %) exist near the source regions. NO x decreases over the source regions and increases in the remote troposphere, due mainly to more efficient transport of peroxyacetyl nitrate (PAN), which is increased with the SAPRC aromatic chemistry. Model ozone mixing ratios with the updated aromatic chemistry increase by up to 5 ppb (more than 10 %), especially in industrially polluted regions. The ozone change is partly due to the direct influence of aromatic oxidation products on ozone production rates, and in part to the altered spatial distribution of NOx that enhances the tropospheric ozone production efficiency. Improved representation of aromatics is important to simulate the tropospheric oxidation.

Sources Profiles of Volatile Organic Compounds (VOCs) Measured in a Typical Industrial Process in Wuhan, Central China

Industrial emission is an important source of ambient volatile organic compounds (VOCs) in Wuhan City, Hubei Province, China. We collected 53 VOC samples from petrochemical, surface coating, electronic manufacturing, and gasoline evaporation using stainless canisters to develop localized source profiles. Concentrations of 86 VOC species, including hydrocarbons, halocarbons, and oxygenated VOCs, were quantified by a gas chromatography–flame ionization detection/mass spectrometry system. Alkanes were the major constituents observed in the source profile from the petrochemical industry. Aromatics (79.5~81.4%) were the largest group in auto-painting factories, while oxygenated VOCs (82.0%) and heavy alkanes (68.7%) were dominant in gravure printing and offset printing factories, respectively. Acetone was the largest contributor and the most frequently monitored species in printed circuit board (PCB) manufacturing, while VOC species emitted from integrated chip (IC) were characterized by high contents of isopropanol (56.4–98.3%) and acetone (30.8%). Chemical compositions from vapor of gasoline 92#, 93#, and 98# were almost identical. Alkanes were the dominant VOC group, with i-pentane being the most abundant species (31.4–37.7%), followed by n-butane and n-pentane. However, high loadings of heavier alkanes were observed in the profile of diesel evaporation.

Ambient volatile organic compounds (VOCs) in communities of the Athabasca oil sands region: Sources and screening health risk assessment

An investigation of ambient levels and sources of volatile organic compounds (VOCs) and associated public health risks was carried out at two northern Alberta oil sands communities (Fort McKay and Fort McMurray located < 25 km and >30 km from oil sands development, respectively) for the period January 2010-March 2015. Levels of total detected VOCs were comparatively similar at both communities (Fort McKay: geometric mean = 22.8 μg/m³, interquartile range, IQR = 13.8-41 μg/m³); (Fort McMurray: geometric mean = 23.3 μg/m³, IQR = 12.0-41 μg/m³). In general, methanol (24%-50%), alkanes (26%-32%) and acetaldehyde (23%-30%) were the predominant VOCs followed by acetone (20%-24%) and aromatics (∼9%). Mean and maximum ambient concentrations of selected hazardous VOCs were compared to health risk screening criteria used by United States regulatory agencies. The Positive matrix factorization (PMF) model was used to identify and apportion VOC sources at Fort McKay and Fort McMurray. Five sources were identified at Fort McKay, where four sources (oil sands fugitives, liquid/unburned fuel, ethylbenzene/xylene-rich and petroleum processing) were oil sands related emissions and contributed to 70% of total VOCs. At Fort McMurray six sources were identified, where local sources other than oil sands development were also observed. Contribution of aged air mass/regional transport including biomass burning emissions was ∼30% of total VOCs at both communities. Source-specific carcinogenic and non-carcinogenic risk values were also calculated and were below acceptable and safe levels of risk, except for aged air mass/regional transport (at both communities), and ethylbenzene/xylene-rich (only at Fort McMurray).

Airborne volatile aromatic hydrocarbons at an urban monitoring station in Korea from 2013 to 2015

The concentrations of C₆-C₁₀ volatile aromatic hydrocarbons (AHCs) in air were measured at an urban air quality monitoring station in Jong-Ro, Seoul, Korea, between 2013 and 2015. Their temporal patterns (e.g., diurnal, intraweek, daily) were assessed individually and collectively as groups of benzene, toluene, ethylbenzene, styrene, and xylene (BTESX); total aliphatic hydrocarbon (TALHC: C₂-C₁₂); total aromatic hydrocarbon (TARHC: C₆-C₁₀); and total hydrocarbon (THC: C₂-C₁₂). The highest mean AHC concentrations over the 3-year study (in ppb (v/v)) were observed for toluene (6.0 ± 4.3), followed by the xylenes (1.5 ± 1.3), ethylbenzene (0.85 ± 0.93), benzene (0.73 ± 0.77), and styrene (0.16 ± 0.30) nL/L. The mean ppbC ((v/v), nL∙atm∙C/nL∙atm) values for BTESX, TALHC, TARHC, and THC were 65.8, 113, 77.7, and 191 ppbC, respectively. For most AHC species (e.g., toluene, styrene, and BTESX), only weak seasonal trends were observed in contrast to temporally varying species like nitric oxide (NO) (e.g., 26.3 ppb (January-February) vs. 8.5 ppb (July-August) during weekdays in 2013). Furthermore, toluene and NO concentrations were much higher (up to a factor 3) on weekdays than on Sunday for most weeks. This might reflect reduced anthropogenic activities on Sunday.

Ambient volatile organic compounds pollution in China

Owing to rapid economic and industrial development, China has been suffering from degraded air quality and visibility. Volatile organic compounds (VOCs) are important precursors to the formation of ground-level ozone and hence photochemical smog. Some VOCs adversely affect human health. Therefore, VOCs have recently elicited public concern and given new impetus to scientific interest. China is now implementing a series of polices to control VOCs pollution. The key to formulating policy is understanding the ambient VOCs pollution status. This paper mainly analyzes the species, levels, sources, and spatial distributions of VOCs in ambient air. The results show that the concentrations of ambient VOCs in China are much higher than those of developed countries such as the United States and Japan, especial benzene, which exceeds available standards. At the same time, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of various VOCs are calculated. Aromatics and alkenes have much higher OFPs, while aromatics have higher SOAFP. The OFPs of ambient VOCs in the cities of Beijing, Guangzhou and Changchun are very high, and the SOAFP of ambient VOCs in the cities of Hangzhou, Guangzhou and Changchun are higher.

VOC emission rates over London and South East England obtained by airborne eddy covariance

Volatile organic compounds (VOCs) originate from a variety of sources, and play an intrinsic role in influencing air quality. Some VOCs, including benzene, are carcinogens and so directly affect human health, while others, such as isoprene, are very reactive in the atmosphere and play an important role in the formation of secondary pollutants such as ozone and particles. Here we report spatially-resolved measurements of the surface-to-atmosphere fluxes of VOCs across London and SE England made in 2013 and 2014. High-frequency 3-D wind velocities and VOC volume mixing ratios (made by proton transfer reaction – mass spectrometry) were obtained from a low-flying aircraft and used to calculate fluxes using the technique of eddy covariance. A footprint model was then used to quantify the flux contribution from the ground surface at spatial resolution of 100 m, averaged to 1 km. Measured fluxes of benzene over Greater London showed positive agreement with the UK’s National Atmospheric Emissions Inventory, with the highest fluxes originating from central London. Comparison of MTBE and toluene fluxes suggest that petroleum evaporation is an important emission source of toluene in central London. Outside London, increased isoprene emissions were observed over wooded areas, at rates greater than those predicted by a UK regional application of the European Monitoring and Evaluation Programme model (EMEP4UK). This work demonstrates the applicability of the airborne eddy covariance method to the determination of anthropogenic and biogenic VOC fluxes and the possibility of validating emission inventories through measurements.

Twelve-year trends in ambient concentrations of volatile organic compounds in a community of the Alberta Oil Sands Region, Canada

Environmental exposure to volatile organic compounds (VOCs) in ambient air is one of a number of concerns that the First Nation Community of Fort McKay, Alberta has related to development of Canada's oil sands. An in-depth investigation of trends in ambient air VOC levels in Fort McKay was undertaken to better understand the role and possible significance of emissions from Alberta's oil sands development. A non-parametric trend detection method was used to investigate trends in emissions and ambient VOC concentrations over a 12-year (2001-2012) period. Relationships between ambient VOC concentrations and production indicators of oil sands operations around Fort McKay were also examined. A weak upward trend (significant at 90% confidence level) was found for ambient concentrations of total VOCs based on sixteen detected species with an annual increase of 0.64μg/m(3) (7.2%) per year (7.7μg/m(3) increase per decade). Indicators of production (i.e., annual bitumen production and mined oil sands quantities) were correlated with ambient total VOC concentrations. Only one of 29 VOC species evaluated (1-butene) showed a statistically significant upward trend (p=0.05). Observed geometric (arithmetic) mean and maximum ambient concentrations of selected VOCs of public health concern for most recent three years of the study period (2010-2012) were below chronic and acute health risk screening criteria of the U.S. Agency for Toxic Substances and Disease Registry and U.S. Environmental Protection Agency. Thirty-two VOCs are recommended for tracking in future air quality investigations in the community to better understand whether changes are occurring over time in relation to oil sands development activities and to inform policy makers about whether or not these changes warrant additional attention.

Volatile organic compounds (VOCs) in surface coating materials: Their compositions and potential as an alternative fuel

A sampling system was designed to determine the composition ratios of VOCs emitted from 31 surface coating materials (SCMs). Representative architectural, automotive, and marine SCMs in Korea were investigated. Toluene, ethylbenzene, and xylene were the predominant VOCs. The VOC levels (wt%) from automotive SCMs were significantly higher than those from architectural and marine paints. It was found that target SCMs comprised mainly VOCs with 6-10 carbon atoms in molecules, which could be adsorbed by activated carbon. The saturated activated carbon which had already adsorbed toluene, ethylbenzene, and m-xylene was combusted. The saturated activated carbon was more combustible than new activated carbon because it comprised inflammable VOCs. Therefore, it could be an alternative fuel when using in a "fuelization system". To use the activated carbon as a fuel, a control technology of VOCs from a coating process was also designed and introduced.

Forecasting of VOC emissions from traffic and industry using classification and regression multivariate methods

In this study, advanced multivariate methods were applied for VOC source apportionment and subsequent short-term forecast of industrial- and vehicle exhaust-related contributions in Belgrade urban area (Serbia). The VOC concentrations were measured using PTR-MS, together with inorganic gaseous pollutants (NOx, NO, NO2, SO2, and CO), PM10, and meteorological parameters. US EPA Positive Matrix Factorization and Unmix receptor models were applied to the obtained dataset both resolving six source profiles. For the purpose of forecasting industrial- and vehicle exhaust-related source contributions, different multivariate methods were employed in two separate cases, relying on meteorological data, and on meteorological data and concentrations of inorganic gaseous pollutants, respectively. The results indicate that Boosted Decision Trees and Multi-Layer Perceptrons were the best performing methods. According to the results, forecasting accuracy was high (lowest relative error of only 6%), in particular when the forecast was based on both meteorological parameters and concentrations of inorganic gaseous pollutants.

Investigation of carbonyl compound sources at a rural site in the Yangtze River Delta region of China

Carbonyl compounds are important intermediates in atmospheric photochemistry, but their primary sources are still not understood well. In this work, carbonyls, hydrocarbons, and alkyl nitrates were continuously measured during November 2011 at a rural site in the Yangtze River Delta region of China. Mixing ratios of carbonyls and hydrocarbons showed large fluctuations during the entire measurement. The average level for total measured volatile organic compounds during the pollution episode from 25th to 27th November, 2011 was 91.6 ppb, about 7 times the value for the clean period of 7th-8th, November, 2011. To preliminarily identify toluene sources at this site, the emission ratio of toluene to benzene (T/B) during the pollution episode was determined based on photochemical ages derived from the relationship of alkyl nitrates to their parent alkanes. The calculated T/B was 5.8 ppb/ppb, significantly higher than the values of 0.2-1.7 ppb/ppb for vehicular exhaust and other combustion sources, indicating the dominant influence of industrial emissions on ambient toluene. The contributions of industrial sources to ambient carbonyls were then calculated using a multiple linear regression fit model that used toluene and alkyl nitrates as respective tracers for industrial emission and secondary production. During the pollution episode, 18.5%, 69.0%, and 52.9% of measured formaldehyde, acetaldehyde, and acetone were considered to be attributable to industrial emissions. The emission ratios relative to toluene for formaldehyde, acetaldehyde, and acetone were determined to be 0.10, 0.20 and 0.40 ppb/ppb, respectively. More research on industrial carbonyl emission characteristics is needed to understand carbonyl sources better.

Sources of C₂-C₄ alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region

Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control.

Speciation of non-methane hydrocarbons (NMHCs) from anthropogenic sources in Beirut, Lebanon

The chemical composition of emissions from the different anthropogenic sources of non-methane hydrocarbons (NMHC) is essential for modeling and source apportionment studies. The speciated profiles of major NMHC sources in Lebanon, including road transport, gasoline vapor, power generation, and solvent use were established. Field sampling have been carried out by canisters in 2012. Around 67 NMHC (C2 to C9) were identified and quantified by using a gas chromatograph equipped with a flame ionization detector. Typical features of the roadway emissions included high percentages of isopentane, butane, toluene, xylenes, ethylene, and ethyne. Gasoline evaporation profiles included high percentage of the C4-C5 saturated hydrocarbons reaching 59 %. The main compounds of the power generator emissions are related to combustion. Toluene and C8-C9 aromatics were the most abundant species in emissions from paint applications. Finally, the impact of the use of region-specific source profile is tackled regarding the implication on air quality.

Benzene homologues in environmental matrixes from a pesticide chemical region in China: Occurrence, health risk and management

The contamination status and health risks of benzene, toluene, ethylbenzene and xylene (BTEX) in air, soil, dust and groundwater were evaluated in a pesticide chemical region located in Hebei province, China. The concentrations of BTEX in air ranged from 7.80 to 238ug/m(3) and those in soil and dust ranged from lower than limit of detection (LOD) to 32,360ng/g dw, and those in groundwater varied from 2.68 to 98.6ug/L. Generally, the levels of BTEX in multimedia matrixes were all below the standards established in China. Health risk assessment was performed based on the monitoring data via inhalation, dermal contact and ingestion pathways and hazard quotient (HQ) was calculated to be on the order of 10(-7), below 10(-6), and Hazard index (HI) levels of BTEX were lower than 1.0. However, both HQ and HI ascended with an increase in work experience/exposure. Integrated risk management was proposed to eliminate BTEX pollution and to protect occupational health of workers in those industries.

Temporal variation of volatile organic compounds and their major emission sources in Seoul, Korea

This study examines the characteristics of volatile organic compounds (VOCs) and their major emission sources at the Bulgwang site in Seoul, Korea. The annual levels of VOCs (96.2-121.1 ppb C) have shown a decreasing trend from 2004 to 2008. The most abundant component in Seoul was toluene, which accounted for over 23.5 % of the total VOCs on the parts per billion on a carbon basis, and the portions of alkanes with two to six carbons constituted the largest major lumped group, ranging from 40.1 to 48.4 % (45.3 ± 3.7 %) of the total VOCs. Major components of the solvent (toluene, m/p-xylene, o-xylene, and ethylbenzene) showed high in daytime and summer and low in nighttime and winter due mainly to the variation of the ambient temperature. The species mostly emitted from gasoline vapor (i/n-butane, i/n-pentane, n-hexane, and 2-methylpentane) and vehicular exhaust (ethylene, acetylene, and benzene) showed bimodal peaks in the diurnal variation around the commuting hours because of the high traffic volume. For the 14 out of 15 highest concentration species, the weekend effect was only evident on Sundays because of the stepwise implementation of the 5-day work-week system. Principal components analysis (PCA) was applied in order to identify the sources of the 15 highest concentration VOCs and, as a result, three principal components such as gasoline vapor (48.9 %), vehicular exhaust (17.9 %), and evaporation of solvents (9.8 %) were obtained to explain a total of 76.6 % of the data variance. Most influential contributing sources at the sampling site were traffic-related ones although the use of solvent was the dominant emission source based on the official emission inventory.

C5-C12 volatile organic compounds at roadside, residential, and background locations in Ankara, Turkey: temporal and spatial variations and sources

Concentrations of 91 volatile organic compounds (VOCs) ranging from C5 to C12 were measured at three sites in Ankara, the capital of Turkey, in the summer of 2003 and winter of 2004. Samples were collected at roadside, residential and background stations at consecutive 4-hr intervals over a 24-hr period for six weeks in each season. Air samples were collected onto cartridges packed with Tenax TA and Carbopack B resins and analyzed by thermal desorption, followed by gas chromatography coupled to a mass selective detector (GC/MSD). Time resolved data provided information on ambient levels, temporal and spatial variations and sources of VOCs in Ankara. Toluene is the most abundant compound at all sites with and average concentration of 13.1 ?g m(-3). The mean concentrations of benzene are 12.6, 5.2, and 2.4 ?g m(-3) during winter at roadside, residential and background stations, respectively. Diurnal variation in the data together with toluene to benzene concentration ratio (T:B) that is close to 2.0 indicated the influence of traffic related emissions at residential and roadside stations during winter season. Higher T:B ratio observed at residential and background stations during summer period and correlation analysis indicated additional VOC sources. Temporal variations and low m,p-xylene to ethylbenzene ratio (mpX:E) indicated that transported air mass is the major VOC source influencing VOC concentrations measured at the background station.

Industrial sector-based volatile organic compound (VOC) source profiles measured in manufacturing facilities in the Pearl River Delta, China

Industrial sector-based VOC source profiles are reported for the Pearl River Delta (PRD) region, China, based source samples (stack emissions and fugitive emissions) analyzed from sources operating under normal conditions. The industrial sectors considered are printing (letterpress, offset and gravure printing processes), wood furniture coating, shoemaking, paint manufacturing and metal surface coating. More than 250 VOC species were detected following US EPA methods TO-14 and TO-15. The results indicated that benzene and toluene were the major species associated with letterpress printing, while ethyl acetate and isopropyl alcohol were the most abundant compounds of other two printing processes. Acetone and 2-butanone were the major species observed in the shoemaking sector. The source profile patterns were found to be similar for the paint manufacturing, wood furniture coating, and metal surface coating sectors, with aromatics being the most abundant group and oxygenated VOCs (OVOCs) as the second largest contributor in the profiles. While OVOCs were one of the most significant VOC groups detected in these five industrial sectors in the PRD region, they have not been reported in most other source profile studies. Such comparisons with other studies show that there are differences in source profiles for different regions or countries, indicating the importance of developing local source profiles.

Source attributions of hazardous aromatic hydrocarbons in urban, suburban and rural areas in the Pearl River Delta (PRD) region

Aromatic hydrocarbons (AHs) are both hazardous air pollutants and important precursors to ozone and secondary organic aerosols. Here we investigated 14 C6-C9 AHs at one urban, one suburban and two rural sites in the Pearl River Delta region during November-December 2009. The ratios of individual aromatics to acetylene were compared among these contrasting sites to indicate their difference in source contributions from solvent use and vehicle emissions. Ratios of toluene to benzene (T/B) in urban (1.8) and suburban (1.6) were near that of vehicle emissions. Higher T/B of 2.5 at the rural site downwind the industry zones reflected substantial contribution of solvent use while T/B of 0.8 at the upwind rural site reflected the impact of biomass burning. Source apportionment by positive matrix factorization (PMF) revealed that solvent use, vehicle exhaust and biomass burning altogether accounted for 89-94% of observed AHs. Vehicle exhaust was the major source for benzene with a share of 43-70% and biomass burning in particular contributed 30% to benzene in the upwind rural site; toluene, C8-aromatics and C9-aromatics, however, were mainly from solvent use, with contribution percentages of 47-59%, 52-59% and 41-64%, respectively.

Evaluation of the optimum volatile organic compounds control strategy considering the formation of ozone and secondary organic aerosol in Seoul, Korea

The characteristics of volatile organic compounds (VOCs) and their annual trends in Seoul, Korea were investigated, with their optimal control strategy suggested. The annual concentration of VOCs (96.2-121.1 ppbC) has shown a decreasing trend from 2004 to 2008, suggesting the control strategy via the "Special Measures for Metropolitan Air Quality Improvement," which was implemented in 2005, has been successful. The contributions of individual VOC to the production of ambient ozone and secondary organic aerosol (SOA) are discussed to assess the adequacy of current control strategies. The contribution of aromatics (C6-C10) to the production of ozone accounted for 38.7-46.3 % of the total ozone production, followed by low carbon alkanes (C2-C6) (27.0-35.9 %). The total SOA formation potential of VOCs was found to range from 2.5 to 3.5 μg m(-3), mainly as a result of aromatics (C6-C10) (over 85 %). Considering the contributions from ozone and SOA production, it was concluded that solvent use was the most important emission source, followed by vehicle exhaust emissions. Thus, the current emission control strategy focused on these two emission sources is appropriate to reduce the VOCs related pollution level of the Seoul Metropolitan Region. Still, an additional control strategy, such as controlling the emissions from meat cooking, which is an emission source of high carbon alkanes (C7-C10), needs to be considered to further reduce the VOCs related pollution level in Seoul.

Characterizations of volatile organic compounds during high ozone episodes in Beijing, China

Air samples were collected in Beijing from June through August 2008, and concentrations of volatile organic compounds (VOCs) in those samples are here discussed. This sampling was performed to increase understanding of the distributions of their compositions, illustrate the overall characteristics of different classes of VOCs, assess the ages of air masses, and apportion sources of VOCs using principal compound analysis/absolute principal component scores (PCA/APCS). During the sampling periods, the relative abundance of the four classes of VOCs as determined by the concentration-based method was different from that determined by the reactivity approach. Alkanes were found to be most abundant (44.3-50.1%) by the concentration-based method, but aromatic compounds were most abundant (38.2-44.5%) by the reactivity approach. Aromatics and alkenes contributed most (73-84%) to the ozone formation potential. Toluene was the most abundant compound (11.8-12.7%) during every sampling period. When the maximum incremental reactivity approach was used, propene, toluene, m,p-xylene, 1-butene, and 1,2,4-trimethylbenzene were the five most abundant compounds during two sampling periods. X/B, T/B, and E/B ratios in this study were lower than those found in other cities, possibly due to the aging of the air mass at this site. Four components were extracted from application of PCA to the data. It was found that the contribution of vehicle exhaust to total VOCs accounted for 53% of VOCs, while emissions due to the solvent use contributed 33% of the total VOCs. Industrial sources contributed 3% and biogenic sources contributed 11%. The results showed that vehicle exhausts (i.e., unburned vehicle emissions + vehicle internal engine combustion) were dominant in VOC emissions during the experimental period. The solvent use made the second most significant contribution to ambient VOCs.

VOC composition of current motor vehicle fuels and vapors, and collinearity analyses for receptor modeling

The formulation of motor vehicle fuels can alter the magnitude and composition of evaporative and exhaust emissions occurring throughout the fuel cycle. Information regarding the volatile organic compound (VOC) composition of motor fuels other than gasoline is scarce, especially for bioethanol and biodiesel blends. This study examines the liquid and vapor (headspace) composition of four contemporary and commercially available fuels: gasoline (<10% ethanol), E85 (85% ethanol and 15% gasoline), ultra-low sulfur diesel (ULSD), and B20 (20% soy-biodiesel and 80% ULSD). The composition of gasoline and E85 in both neat fuel and headspace vapor was dominated by aromatics and n-heptane. Despite its low gasoline content, E85 vapor contained higher concentrations of several VOCs than those in gasoline vapor, likely due to adjustments in its formulation. Temperature changes produced greater changes in the partial pressures of 17 VOCs in E85 than in gasoline, and large shifts in the VOC composition. B20 and ULSD were dominated by C(9) to C(16)n-alkanes and low levels of the aromatics, and the two fuels had similar headspace vapor composition and concentrations. While the headspace composition predicted using vapor-liquid equilibrium theory was closely correlated to measurements, E85 vapor concentrations were underpredicted. Based on variance decomposition analyses, gasoline and diesel fuels and their vapors VOC were distinct, but B20 and ULSD fuels and vapors were highly collinear. These results can be used to estimate fuel related emissions and exposures, particularly in receptor models that apportion emission sources, and the collinearity analysis suggests that gasoline- and diesel-related emissions can be distinguished.

Environmental risk assessment and concentration trend of atmospheric volatile organic compounds in Hyogo Prefecture, Japan

PURPOSE

The purpose of this study was to evaluate the influences of volatile organic compounds (VOCs) emissions on hazardousness and photochemical reactivity and to propose efficient VOCs abatement strategies.

METHODS

The atmospheric concentrations of 101 components of VOCs were measured at six sites which comprehend four urban areas, a roadside area, and an industrial area in Hyogo Prefecture. VOCs influence on hazardousness and photochemical reactivity were evaluated using VOCs measured data and the index on the health effect evaluation and ozone formation potential. The substances that require emissions reduction were selected from the evaluation results. The state and characteristics of environmental pollution were considered from the concentration trends of the selected substances.

RESULTS

In industrial area, n-hexadecane, styrene, vinyl chloride monomer, and 1,2-dichloroethane showed a high concentration. In roadside area, n-hexane, n-undecane, n-dodecane, tetrachloroethylene, formaldehyde, acetaldehyde, and 1-butanol showed a high concentration. The excess cancer incidences for formaldehyde exceeded 10(-5) of the level of concern for carcinogenic effect at all sites. Toluene had a high percentage of ozone production. The interannual and seasonal trends of toluene concentrations were different at a regional level and the formaldehyde concentrations in summer were significantly higher than those in winter at the urban sites.

CONCLUSIONS

The results show the need to prepare the emission reduction plan for the major sources such as vehicle exhaust, solvent use, and industrial processes to diminish the concentration of toluene that contributes significantly to the formation of photochemical oxidant.

Characterization of volatile organic compounds in the urban area of Beijing from 2000 to 2007

Beijing is one of the most polluted cities in the world. In this study, the long-term and continuous measurements of volatile organic compounds (VOCs) in the urban area of Beijing, specifically at Beijing 325 m Meteorological Tower, were conducted from 2000 to 2007. The annual record of VOC trends exhibited in two different phases was separated in 2003. Records show that VOC concentrations increased from 2000 to 2003 due to the abrupt increase in vehicle number. Contrarily, since 2003, there had been a decrease in VOCs concentrations as the policy on gasoline and air pollution was implemented. Toluene, benzene, and i-pentane are the chemicals that abound in and are directly related to vehicle activity, such as in vehicle exhaust and gasoline evaporation. Furthermore, records indicate that there had been seasonal variation in VOCs levels in that VOCs level in summer is higher than that in winter. As such, temperature is considered to significantly contribute to VOCs in Beijing. Records also show that VOCs level was high in the morning and during rush hours in the evening. In contrast, VOCs level was low during midday due to photochemical destruction with OH radical and dilution effect. In this study, a particular benzene to toluene ratio range (0.4-1.0) was used as the indicator of air propelled by vehicular exhaust. We also applied the correlation coefficients between BTEX and i-pentane to evaluate evaporation influence to ambient BTEX in the Beijing urban area.

Personal, indoor, and outdoor exposure to VOCs in the immediate vicinity of a local airport

This study measures the effect of emissions from an airport on the air quality of surrounding neighborhoods. The ambient concentrations of benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) were measured using passive samplers at 15 households located close to the airport (indoor, outdoor, and personal), at the end of airport runways and an out-of-neighborhood location. Measurements occurred over a 48-h period during summer 2006 and winter 2006-2007. The average concentrations were 0.84, 3.21, 0.30, 0.99, and 0.34 μg/m3 at the airport runways and 0.84, 3.76, 0.39, 1.22, and 0.39 μg/m3 in the neighborhood for benzene, toluene, ethylbenzene, m-, p-, and o-xylene. The average neighborhood concentrations were not significantly different to those measured at the airport runways and were higher than the out-of-neighborhood location (0.48, 1.09, 0.15, 0.78, and 0.43 μg/m3, each BTEX). B/T ratios were used as a tracer for emission sources and the average B/T ratio at the airport and outdoors were 0.20 and 0.23 for the summer and 0.40 and 0.42 for the winter, suggesting that both areas are affected by the same emission source. Personal exposure was closely related to levels in the indoor environment where subjects spent most of their time. Indoor/outdoor (I/O) ratios for BTEX ranged from 1.13 to 2.60 and 1.41 to 3.02 for summer and winter. The seasonal differences in I/O ratios reflected residential ventilation patterns, resulting in increased indoor concentrations of volatile organic compounds during winter.

Indoor-outdoor distribution and risk assessment of volatile organic compounds in the atmosphere of industrial and urban areas

Volatile organic compounds (VOCs), which play an important part indoors and outdoors, comprise differing compound groups such as n-alkanes, cycloalkanes, aromatic and chlorinated hydrocarbons and terpenes. In the current study, samples were analyzed from indoor (schools and houses, n = 92) and outdoor (n = 33) air in urban, industrial, semirural and residential areas from the region of La Plata (Argentine) to consider VOC exposure in different types of environments. VOCs were sampled for 1 month during winter for 3 years, with passive 3M monitors. Samples were extracted with CS(2) and analyzed by GC/MS detectors. The results show significant differences in concentration and distribution between indoor and outdoor samples, depending on the study area. Most VOCs predominantly originated indoors in urban, semirural and residential areas, whereas an important outdoor influence in the industrial area was observed. In all areas alkanes and aromatic compounds dominated, even though a different chemical distribution was seen. Traffic burden was determined as the major source of outdoor VOC with a benzene/toluene ratio close to 0.5. Indoors, C9-C11 alkanes, toluene and xylenes dominated, caused by human activities. In contrast, in the industrial area higher concentrations of hexane, heptane and benzene occurred outdoors and affected the indoor air significantly. The lifetime cancer risk (LCR) associated to the benzene exposure was calculated for children from the different study areas. For all groups the study showed a LCR value greater than 1 x 10(-6) related to the benzene exposure indoors as well outdoors. A value two magnitudes higher was detected indoors in the industrial area, what demonstrates the high risk for children living in this area of La Plata.