The submicron particulate matter(PM1)and fine particulate matter(PM2.5)are very impor-tant due to their greater adverse impacts on the natural environment and human health.In this study,the daily PM1 and PM2.5 samples were collected during early summer 2018 at a sub-urban site in the urban-industrial port city of Tianjin,China.The collected sam-ples were analyzed for the carbonaceous fractions,inorganic ions,elemental species,and specific marker sugar species.The chemical characterization of PM1 and PM2.5 was based on their concentrations,compositions,and characteristic ratios(PM1/PM2.5,AE/CE,NO3-/SO42-,OC/EC,SOC/OC,OM/TCA,K+/EC,levoglucosan/K+,V/Cu,and V/Ni).The average concen-trations of PM1 and PM2.5 were 32.4 pg/m3 and 53.3 pg/m3,and PM1 constituted 63％of PM2.5 on average.The source apportionment of PM1 and PM2.5 by positive matrix factoriza-tion(PMF)model indicated the main sources of secondary aerosols(25％and 34％),biomass burning(17％and 20％),traffic emission(20％and 14％),and coal combustion(17％and 14％).The biomass burning factor involved agricultural fertilization and waste incineration.The biomass burning and primary biogenic contributions were determined by specific marker sugar species.The anthropogenic sources(combustion,secondary particle formation,etc)contributed significantly to PM1 and PM2.5,and the natural sources were more evident in PM2.5.This work significantly contributes to the chemical characterization and source ap-portionment of PM1 and PM2.5 in near-port cities influenced by the diverse sources.