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Intermediate volatility organic compounds (IVOCs) from mobile sources contribute significantly to secondary organic aerosol (SOA) formation. However, the assessments of IVOC emissions remain considerably uncertain due to the lack of localized measured data and detailed emission source classifications. This study established a comprehensive database of IVOC emission factors (EFs) for mobile sources based on the diversified measured EFs and correlations with hydrocarbons. The provincial-level IVOC emission inventories over China were further established by integrating activity data of various mobile sources. The national mobile source IVOC emissions were 507.5 Gg in 2017. The IVOC emissions of on-road and non-road mobile sources were roughly the same. Trucks and non-road construction machineries were the major contributors to IVOC emissions, accounting for >66 % of the total. The IVOC emission characteristics and spatial distributions from various mobile sources varied significantly with different types and usages. The IVOC emission inventories with detailed classifications can be used to evaluate emission control policies for mobile sources. Incorporating localized measured data would be beneficial for a better understanding for the atmospheric impacts of mobile source IVOC emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Semivolatile/intermediate-volatility organic compounds (S/IVOCs) from mobile sources are essential SOA contributors. However, few studies have comprehensively evaluated the SOA contributions of S/IVOCs by simultaneously comparing different parameterization schemes. This study used three SOA schemes in the CMAQ model with a measurement-based emission inventory to quantify the mobile source S/IVOC-induced SOA (MS-SI-SOA) for 2018 in China. Among different SOA schemes, SOA predicted by the 2D-VBS scheme was in the best agreement with observations, but there were still large deviations in a few regions. Three SOA schemes showed the peak value of annual average MS-SI-SOA was up to 0.6 ± 0.3 μg/m 3 . High concentrations of MS-SI-SOA were detected in autumn, while the notable relative contribution of MS-SI-SOA to total SOA was predicted in the coastal areas in summer, with a regional average contribution up to 20 ± 10% in Shanghai. MS-SI-SOA concentrations varied by up to 2 times among three SOA schemes, mainly due to the discrepancy in SOA precursor emissions and chemical reactions, suggesting that the differences between SOA schemes should also be considered in modeling studies. These findings identify the hotspot areas and periods for MS-SI-SOA, highlighting the importance of S/IVOC emission control in the future upgrading of emission standards.

In this study, real-time measurement of Volatile Organic Compounds (VOCs) was conducted at an urban site in Changzhou, a typical corridor city in the Yangtze River Delta (YRD) region in China, by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) during 2019 China International Import Expo (CIIE) episode. An improved method based on Air Quality Index (AQI) value is applied to identify polluted and clean periods. Diurnal pattern of VOC levels revealed elevated photochemical reactivity during polluted periods. Five VOC sources were identified by Positive Matrix Factorization (PMF) model, including secondary formation (22.71 ± 12.33%), biogenic (21.50% ± 11.76%), solvent usage (20.50 ± 10.07%), vehicle exhaust (18.32 ± 8.32%), and industrial process and fuel usage (16.96 ± 13.21%). The mean contribution of vehicular exhaust was 10.84% higher during the nighttime than the daytime under polluted days. The biogenic source contributed more during clean periods, while the secondary formation presented the opposite. Spatial analysis displayed that the VOC concentration was higher in the S and SSE. In terms of the regional transport, short-distance air masses from the northeast and the south within the YRD region led to high VOC levels and biogenic VOC derived from the ocean might affect the entire region. Stringent emission control policies enforced over the YRD for 2019 CIIE provided an excellent opportunity to determine the source-receptor response. As joint control area, the VOC level of Changzhou exhibited a substantial reduction and the VOC amounts emitted by solvent usage showed the biggest decrease (-58%). The findings of this study highlight the superiority of high time-resolved data in identifying the dynamic variation pattern (with the change of time and wind) of VOC levels and emission intensities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Continuous tightening emission standards (ESs) facilitate the reduction of organic gas emissions from gasoline vehicles. Correspondingly, it is essential to update the emissions and chemical speciation of total organic gases (TOGs), including volatile organic compounds (VOCs), intermediate volatility organic compounds (IVOCs), CH 4 , and unidentified non-methane hydrocarbons (NMHCs) for assessing the formation of ozone and secondary organic aerosol (SOA). In this study, TOG and speciation emissions from 12 in-use light-duty gasoline vehicle (LDGV) exhausts, covering the ESs from China II to China V, were investigated on a chassis dynamometer under the Worldwide Harmonized Light-duty Test Cycle (WLTC) in China. The results showed that the most effectively controlled subgroup in TOG emissions from LDGVs was VOCs, followed by the unidentified NMHCs and IVOCs. The mass fraction of VOCs in TOGs also reduced from 61 ± 9% to 46 ± 18% while the IVOCs gently increased from 2 ± 0.4% to 8 ± 4% along with the more stringent ESs. For the VOC subsets, the removal efficiency of oxygenated VOCs (OVOCs) was lower than those of other VOC subsets in the ESs from China IV to V, suggesting the importance of OVOC emission controls for relatively new LDGVs. The IVOC emissions were mainly subject to the ESs, then driving cycles and fuel use. The formation potentials of ozone and SOA from LDGVs decreased separately 96% and 90% along with the restricted ESs from China II-III to China IV. The major contributor of SOA formation transformed from aromatics in the VOC subsets for China II-III vehicles to IVOCs for China IV/V vehicles, highlighting that IVOC emissions from LDGVs are also needed more attentions to control in future., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Organosulfates (OSs) are an important component of atmospheric organic aerosol (OA) and are widespread in various environments. However, the OSs generated from anthropogenic emissions are poorly understood. In this study, the molecular compositions of OSs from atmospheric PM 2.5 samples collected during a winter measurement campaign (SEISO-Bohai) at Jingtang Harbor were characterized via ultrahigh resolution mass spectrometry (UHRMS). The changes of port OS compositions were observed in episodes of complete haze pollution. As the pollution aggravated, the relative abundances of OSs were apparently increased, and the molecule compositions became more complex, primarily driven by the oxidation and fragmentation processes. Potential OS precursors from traffic emissions were identified based on an optimized "OS precursor map" developed in the previous study. OSs characterized by high molecular weights and low degrees of both unsaturation and oxidization were suggested to mainly derive from secondary reactions of intermediate volatile organic compounds (IVOCs) emitted by traffic sources. These OSs were primarily detected in clean-day samples, followed by decreasing with the pollution process. In addition, our study also finds that ship emissions may further facilitated OS productions under haze pollution conditions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Intermediate-volatility organic compounds (IVOCs) have been found as important sources for secondary organic aerosol (SOA) formation. IVOC emissions from nonroad construction machineries (NRCMs), including two road rollers and three motor graders, were characterized under three operation modes using an improved portable emission measurement system. The fuel-based IVOC emission factors (EFs) of NRCMs varied from 245.85 to 1802.19 mg/kg·fuel, which were comparable at magnitudes to the reported results of an ocean-going ship and on-road diesel vehicles without filters. The discrepancy of IVOC EFs is significant within different operation modes. IVOC EFs under the idling mode were 1.24-3.28 times higher than those under moving/working modes. Unspeciated b -alkanes and cyclic compounds, which were the unresolved components in IVOCs at the molecular level, accounted for approximately 91% of total IVOCs from NRCMs. The SOA production potential analysis shows that IVOCs dominated SOA formation of NRCMs. Our results demonstrate that IVOC emissions from NRCMs are non-negligible. Thus, an accurate estimation of their IVOC emissions would benefit the understanding of SOA formation in the urban atmosphere.