Chemical characteristics and source apportionment of ambient PM_1.0 and PM_2.5 in a polluted city in North China plain

Handan is a heavily polluted city in the northern China. From 6 to December 31, 2015, PM_1.0 and PM_2.5 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 PM_1.0 and PM_2.5 in Handan were as high as 189.2 μg/m³ and 252.4 μg/m³, while the average PM_1.0/PM_2.5 ratio was relatively low (74.6%) compared with the results in megacities. Overall, the chemical characteristics of PM_1.0 and PM_2.5 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 PM_1.0 and PM_2.5. As a result of reduced photochemical reactions, the weights of secondary organic carbon (SOC) in PM_1.0 and PM_2.5 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 PM_1.0 and PM_2.5, 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.