LAUSR

Abstract Handan is a heavily polluted city in the northern China. From 6 to December 31, 2015, PM1.0 and PM2.5 samples were synchronously collected for 23.5 h of each day at an urban site in Handan, to study the chemical composition and sources of aerosols present during wintertime in North China Plain (NCP). The average mass concentrations of PM1.0 and PM2.5 in Handan were as high as 189.2 μg/m3 and 252.4 μg/m3, while the average PM1.0/PM2.5 ratio was relatively low (74.6%) compared with the results in megacities. Overall, the chemical characteristics of PM1.0 and PM2.5 were quite similar during the campaign. During pollution episodes, SNA (sulphate, nitrate, and ammonium) ions were found dramatically increased, while the fraction of organic carbon (OC) and elemental carbon (EC) decreased in both PM1.0 and PM2.5. As a result of reduced photochemical reactions, the weights of secondary organic carbon (SOC) in PM1.0 and PM2.5 decreased during the pollution episode. Besides, liquid water content (LWC) were found effective for SNA formation. The positive matrix factorization (PMF) model identified similar sources distributions for PM1.0 and PM2.5, and the top three contributors were coal combustion, secondary inorganic aerosols, and industrial emissions. Moreover, the potential source contribution function (PSCF) demonstrated that regional sources in southern Handan might be crucial contributors to haze pollution in Handan.