[Characteristics of VOCs and Formation Potentials of O3 and SOA in Autumn and Winter in Tongchuan, China].

Volatile organic compounds (VOCs) are the main precursors of tropospheric O3 and secondary organic aerosol (SOA), which can enhance atmospheric oxidation, promote the formation of secondary pollutants, and affect regional air quality and human health. In order to gain insights on VOCs characteristics and their potentials for O3 and SOA formation, the volume fraction of 102 VOCs in autumn and winter in the urban area of Tongchuan were monitored using the TH-300B online monitoring system. The maximum incremental reactivity (MIR) coefficient and the fractional aerosol coefficient (FAC) were used to estimate the ozone formation potential (OFP) and SOA formation potential (SOAFP), respectively. The φ(TVOC, total VOCs) were (50.52±16.81)×10-9 in autumn and (63.21±35.24)×10-9 in winter. The OFPs were 138.43×10-9 in autumn and 137.123×10-9 in winter, and the SOAFPs were 3.098 µg·m-3 and 0.612 µg·m-3, respectively. Alkanes (26.19%) and aromatics (26.04%) were the most abundant species in autumn, and alkanes (48.88%) were the most abundant species in winter. Trans-2-pentene, toluene, and m/p-xylene were the most reactive species in terms of OFPs in autumn, and ethylene, acetylene, and propylene were the top three species contributing to the total OFPs in winter. Toluene, m/p-xylene, and ethylbenzene contributed the most to the total SOAFPs in both of autumn and winter. Traffic emissions were considered as the major source of VOCs in both seasons. VOCs from biomass/coal combustion emissions showed seasonal differences, which were more prominent in winter. The results can provide references for the "one city, one policy" to mitigate regional VOCs pollution and improve ambient air quality.

Scenario analysis of vehicular emission abatement procedures in Xi'an, China.

Vehicular emissions contribute significantly to air pollution, and the number of vehicles in use is continuing to rise. Policymakers thus need to formulate vehicular emission reduction policies to improve urban air-quality. This study used different vehicle control scenarios to predict the associated potential of mitigating carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxide (NOx), particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5), and particulate matter with an aerodynamic diameter less than 10 µm (PM10) in Xi'an China, in 2020 and 2025. One business-as-usual scenario and six control scenarios were established, and vehicular emission inventory was developed according to each scenario. The results revealed that eliminating high-emission vehicles and optimizing after-treatment devices would effectively reduce vehicular emissions. In addition, increasing the number of alternative fuel vehicles, restraining vehicle use, and restraining the growth of the vehicle population would all have certain effects on CO and VOCs emissions, but the effects would not be significant for NOx, PM2.5, and PM10. The results also indicated that if all control measures were stringently applied together, emissions of CO, VOCs, NOx, PM2.5, and PM10 would be reduced by 51.66%, 51.58%, 30.19%,71.12%, and 71.81% in 2020, and 53.55%, 51.44%, 19.09%, 54.88%, and 55.51%, in 2025, respectively.