Size-segregated atmospheric aerosol particles collected at a suburban site in Qingdao during January and March, 2016 were used to investigate size distributions of ten trace elements in mass concentration as well as their size-dependent solubility in relation to atmospheric acid processes. In general, size distributions of the total mass concentrations of the trace elements exhibited a uni-modal pattern. For example, Fe, Al, Ba and Sr, which are expected to mainly originate from crustal sources, mostly existed in the coarse particles (2.1~7.0μm), and the part mass accounted for 50%~60% of their total mass concentrations. Cd, As, Zn and Pb, which are expected to have strong anthropogenic contributors, were mainly distributed in the range of 0.43~2.1μm where the part mass accounted for 60%~70% of their total concentrations. However, there were no size trend for the total mass of Mn and Ni. The size distributions of water-soluble trace elements in mass concentration also exhibited a unimodal pattern. ~70% of water-soluble Fe, Al, Ba, Sr and Mn are distributed in the broad size range of 0.43~4.7μm, and nearly 80% of soluble Cd, As, Zn and Pb in mass concentration existed in the fine particles at 0.43~2.1μm. No size trend was found for the soluble Ni. The solubility of the trace elements was higher in fine particles than in coarse particles and this is particularly true for those derived from crustal sources. Moreover, the size distributions of the aerosol in-situ pH and the correlations between the pH and the elements' solubility implied that acidification processes in the atmosphere played a key role in determining the size-dependent solubility of the trace elements.