Refined Source Apportionment of Atmospheric PM2.5 in a Typical City in Northwest China

ABSTRACT 

The Xixian New District (XXND), established in 2014, is the seventh national-level new district in China, but research on air pollution there has been limited. This study focused on the characteristics and sources of PM_2.5 in XXND from 2017 to 2018. The average annual PM_2.5 mass was 67 μg m^-3; loadings were high in winter and low in summer. Organic carbon (18.2%), nitrate (17.0%), and sulfate (13.1%) were the main chemical components of PM_2.5. A refined statistical assessment of sources was conducted using the CAS-HERM receptor model, and it showed that primary sources accounted for ~58.5% of the PM_2.5 annual mass, of which dust accounted for 23.3% (road, construction, and soil dust accounted for 11.4%, 8.0% and 3.9%, respectively) while motor vehicles contributed 10.1% (diesels 8.7% and gasoline vehicles 1.4%). Secondary sources for sulfates, nitrates, and organic aerosols accounted for ~41.5% of the PM_2.5 mass. A complementary analysis using the WRF-CHEM model showed that regional transport accounted for 60.8% of the PM_2.5 during the winter high-pollution period, which also implies the importance of secondary aerosols.