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Intermediate-volatility organic compounds (IVOCs) emitted from vehicles are generally in the gas phase but may partly partition into particle phase when measured under ambient temperature. To have a complete and accurate picture of IVOC emissions from vehicles, gas- and particle-phase IVOCs from a fleet of gasoline and diesel vehicles were simultaneously characterized by dynamometer testing in Guangzhou, China. The total IVOC emission factors of the diesel vehicles were approximately 16 times those of the gasoline vehicles, and IVOCs were mainly concentrated in the particle phase in the form of the unresolved complex mixture (UCM). The chemical compositions and volatility distributions of the gas-phase IVOCs differed much between gasoline and diesel vehicles, but were similar to those of their respective fuel content. This indicated that vehicle fuel is the main origin for the gas-phase IVOC emissions from vehicles. In comparison, the chemical compositions of the particle-phase IVOCs from gasoline and diesel vehicles were similar and close to lubricating oil content, implying that lubricating oil plays an important role in contributing to particle-phase IVOCs. The highest IVOC fraction in the particle phase occurred from B 16 -B 18 volatility bins, overall accounting for more than half of the particle-phase IVOCs for both the gasoline and diesel vehicles. A conceptual model was developed to articulate the distributions of lubricating oil contents and their evaporation and nucleation/adsorption capabilities in the different volatility bins. The IVOCs-produced secondary organic aerosol (SOA) were 1.4-2.6 and 3.9-11.7 times POAs emitted from the gasoline and diesel vehicles, respectively. The tightening of emission standards had not effectively reduced IVOC emissions and the SOA production until the implementation of China VI emission standard. This underscores the importance of accelerating the promotion of the latest emission standard to alleviate pollution from vehicles in China., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A compilation of new advances made in the research field of laboratory reaction kinetics in China's Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented. These advances are grouped into six broad, interrelated categories, including volatile organic compound (VOC) oxidation, secondary organic aerosol (SOA) formation, new particle formation (NPF) and gas-particle partitioning, ozone chemistry, model parameters, and secondary inorganic aerosol (SIA) formation, highlighting the laboratory work done by Chinese researchers. For smog chamber applications, the current knowledge gained from laboratory studies is reviewed, with emphasis on summarizing the oxidation mechanisms of long-chain alkanes, aromatics, alkenes, aldehydes/ketones in the atmosphere, SOA formation from anthropogenic emission sources, and oxidation of aromatics, isoprene, and limonene, as well as SIA formation. For flow tube applications, atmospheric oxidation mechanisms of toluene and methacrolein, SOA formation from limonene oxidation by ozone, gas-particle partitioning of peroxides, and sulfuric acid-water (H 2 SO 4 -H 2 O) binary nucleation, methanesulfonic acid-water (MSA-H 2 O) binary nucleation, and sulfuric acid-ammonia-water (H 2 SO 4 -NH 3 -H 2 O) ternary nucleation are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Measurements of volatile organic compounds (VOCs) were performed as well as other pollutants in Shanghai in winter. The whole measurements were classified into three types of periods, including particulate pollution episodes (PPE), VOC pollution episodes (VPE), and relatively clean periods based on the pollution characteristics. Of these types, PPE have the highest fine particulate matter (PM 2.5) mass concentrations and second-highest VOC concentrations, mainly impacted by the regional transport of aged air masses from the northwest. VPE generally concern long-lasting high concentrations of VOCs under stagnant atmospheric conditions due to the accumulation of local emissions. Five sources of VOCs were identified by the positive matrix factorization (PMF) model, and furthermore, the analysis of VOCs concentration weighted trajectory (CWT) was employed to investigate the potential source region and even to validate the source identification to some extent. As a result, VOCs in Shanghai in winter were mainly from solvent usage (23.9%), vehicle emissions mixed with some petrochemical emissions (24.7%), natural gas and background (23.6%), combustion-related to regional transport (22.1%), and secondary formation (5.7%). The regional transport, usually with large combustion sources, played more important roles (41.9%) in VOCs during PPE compared to VPE and clean periods. The contribution of local emissions like vehicle exhaust and petrochemical emissions increased during VPE compared to PPE and clean periods. Clean periods have low PM 2.5 and low VOC concentrations, with a large contribution from the regional background. The present study highlighted the regional transport of VOCs should be taken into account for policymakers when making the city scale controlling measures. • Meteorological conditions strongly influenced VOCs characteristics in winter. • PPE and VPE were two kinds of typical pollution episodes in winter. • Regional transport-related combustion from the northwest played important roles during PPE. • Local emissions dominated the increase of VOCs during VPE. [ABSTRACT FROM AUTHOR]

Intensive field measurements were carried out in urban Shanghai between 20th and 30th of May 2017, and the VOC characteristics and sources were investigated with a focus on the relative contributions of local emissions and regional transport, as well as on the potential source regions. The VOC characteristics and sources largely depended on the meteorological conditions, especially wind direction and wind speed. Generally, two kinds of episodes were associated with regional transport. In one scenario, pollutants were transported from areas upwind (north-to-northwest) of Shanghai, specifically the Suzhou-Wuxi-Changzhou and Nantong city clusters and were characterized by combustion emissions and aged air masses. In the other scenario, pollutants were transported from areas upwind (south-to-southeast) of Shanghai, specifically Ningbo-Zhoushan port, and were characterized by industrial emissions and aged air masses. Additionally, an episode associated with air masses from the clean area over the sea provided an opportunity to study the local emissions of VOCs in Shanghai. Vehicle exhaust and chemical industries, especially solvent usage, contributed a majority of the VOCs in urban Shanghai in summer, together accounting for more than 55%. The aromatic fraction of the PAMS in Shanghai was significantly higher than that in other regions in China. Regional transport and secondary formation were also important sources of VOCs, and their contribution ranged from ~15% to ~25% depending on the meteorological conditions, with an hourly maximum contribution as high as 67%. Fuel evaporation, especially leakage emissions, should be addressed in Shanghai. The present study highlights the fact that joint control of VOCs in conjunction with surrounding cities is critical for Shanghai. Image 1 • VOCs in Shanghai show a strong dependence on meteorological conditions. • Aromatic fractions in Shanghai are higher than those in most regions in China. • Solvent use and vehicle exhaust are the two largest emissions of local VOCs. • Regional transport plays an important role in VOC loading in Shanghai. [ABSTRACT FROM AUTHOR]

Abstract New particle formation (NPF) events are important phenomena that generate nanoparticles and even fine particles via gas-to-particle conversion. These events have clear effects on aerosol loading, atmospheric chemistry and global climate. Long-term field measurements were used to characterize aerosol size distributions and to examine the role of atmospheric volatile organic compounds (VOCs) in NPF events in the urban environment of Shanghai. Aitken and accumulation particles are dominant and account for 85–95% of the total particles, whereas coarse particles are negligible. Particles in the four size-models show the same seasonality: highest in winter and lowest in autumn. The mean particle size distributions display different patterns of diurnal fluctuation, including bimodal in spring and winter, tri-modal in autumn, and "banana" shaped in summer due to highly frequent NPF events. The geometric mean diameter (GMD) is often 20–30 nm or 40–60 nm. Overall, NPF events occur on 89 days out of 335 measurement days (26.5%), and the newly formed particles have a mean growth rate of 6.28 nm h−1. Two typical anthropogenic aromatics, benzene and toluene, from traffic emissions closely match the occurrence of NPF events and have a weakly positive correlation with the nucleation particle number concentrations. The enhanced VOCs as precursors of organic vapors may contribute to the growth process of NPF events to some extent (e.g., growth rate) so that newly formed particles can grow into a detectable size. Highlights • Aitken and accumulation particles account for 85–95% of total particles. • Aerosol size distributions display different diurnal patterns. • The NPFs occur on 89 days out of 335 days with the highest frequency in summer. • Two anthropogenic aromatics have correlations with nucleation particle. • Enhanced VOCs may contribute to the growth of newly formed particles. [ABSTRACT FROM AUTHOR]