Deposition of mineral dust aerosol into open oceans significantly impacts marine biogeochemistry and primary production, and the deposition rates can be constrained using widely measured dissolved aluminum (Al) in surface seawater as a tracer. However, aerosol Al solubility, a critical parameter used in this method, remains highly uncertain. This work investigated seasonal variations of aerosol Al solubility for supermicron and submicron particles at two locations (Xi’an and Qingdao) in northern China. Aerosol Al solubility was found to be very low at Xi’an and much higher at Qingdao. Furthermore, seasonal variability of Al solubility, its correlation with relative abundance of sulfate and nitrate, and its dependence on relative humidity (RH), are all different at the two locations. We suggest that all the features observed for aerosol Al solubility at the two locations can be well explained by the effects of atmospheric chemical processing. Mineral dust transported to Xi’an (an inland city in Northwest China) was still not significantly aged and thus chemical processing had little effects on aerosol Al solubility. After arriving at Qingdao (a coastal city in the Northwest Pacific), mineral dust was substantially aged by chemical processing, leading to substantial enhancement in aerosol Al solubility. Our work further reveals that aerosol liquid water and acidity play vital roles in the dissolution of aerosol Al by atmospheric chemical processing. We suggest that spatial variation of aerosol Al solubility should be taken into account so that oceanic dust deposition can be better constrained using dissolved Al concentrations in surface seawater.