Chemical composition of PM2.5 in an urban environment in Chengdu, China: Importance of springtime dust storms and biomass burning

► Major chemical components of PM2.5 were identified in each season. ► Dust storms occasionally affected PM2.5 composition in spring. ► Biomass burning significantly changed PM2.5 composition in late spring to early summer. ► Major sources for PM2.5 include secondary sulfate/nitrate, motor vehicles and road dust, soil dust and others, and biomass burning.