Abstract: Ambient PM₁₀ samples were collected at six sites and ambient PM_2.5 samples were collected at two sites, respectively during the years 2011-2012in Qingdao. The mass concentration, inorganic elements, water solvent ions and carbon species were analyzed to identify the sources of PM₁₀ and PM_2.5. Meanwhile, the concentrations and chemical compositions of PM₁₀ and PM_2.5 were explored and compared. Source categories were identified and the contributions of primary and secondary sources of PM₁₀ and PM_2.5 were determined using a CMB-iteration model, which could directly estimate the SOC concentrations in the ambient receptors without introducing the SOC profile. Simultaneously, statistical methods (enrichment factors and divergence coefficients) were applied to reveal the source characteristics and chemical compositions of particulate materials. The results showed that:the concentrations of PM₁₀ and PM_2.5 significantly changed in different seasons being greatest in spring and winter and lowest in summer and autumn. The enrichment factors of chemical compositions suggested that the elements, Na, Mg, Al, Si, Ca and Fe, dominated in PM₁₀, while SO₄^2-, NO₃^-, EC and OC were rich in PM_2.5. The contributions of resuspended dust, coal combustion dust, construction and cement dust and sea salt were higher in PM₁₀ than in PM_2.5, with the contributions of 28.7%, 17.2%, 7.16% and 4.47%, respectively; while the contributions of secondary sulfate, secondary nitrate, vehicle exhaust and secondary organic carbon were higher in PM_2.5 than in PM₁₀, with contributions of 19.3%, 8.97%, 13.7% and 6.07%, respectively. The divergence coefficients of the chemical components of particulate matter were calculated for the samples of different seasons. The results showed that the chemical components were heterogeneous in spring and autumn and homogeneous in summer and winter.