| Summary: | With the rapid increase of the vehicle population in the Guanzhong Plain (GZP), the fine particulate matter (PM<sub>2.5</sub>) emitted by vehicles has an impact on regional air quality and public health. The spatial distribution of primary and secondary PM<sub>2.5</sub> concentrations from vehicles in GZP in January and July 2017 was simulated in this study by using the Weather Research and Forecasting (WRF) model and the California Puff (CALPUFF) air quality model. The contributions of vehicle-related emission sources to total PM<sub>2.5</sub> concentrations were also calculated. The results show that although the emissions of primary PM<sub>2.5</sub>, NOx, and SO<sub>2</sub> in July were greater than those in January, the hourly average concentrations of primary and secondary PM<sub>2.5</sub> in January were significantly higher than those in July. The highest concentrations of primary and total PM<sub>2.5</sub> were mostly located in the urban areas of Xi’an and Xianyang in the central region of GZP. The contributions of exhaust emissions, secondary nitrates, brake wear, tire wear, and secondary sulfate to the total PM<sub>2.5</sub> concentrations in GZP were 50.37%, 34.76%, 10.79%, 4.06%, and 0.04% in January and 71.91%, 11.14%, 11.89%, 5.03%, and 0.03% in July, respectively. These results will help us to further control PM<sub>2.5</sub> pollution caused by vehicles.
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