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Although biogenic aerosols play important roles in atmospheric processes and climate change, their contributions to atmospheric particulate matter mass have not received much attention, partly due to the difficulty in identifying key aerosol components and due to the often dominant role of anthropogenic emissions. In order to estimate contributions of biogenic and biomass burning organic aerosols to atmospheric particles, fine particulate matter (PM2.5) samples were collected simultaneously at an urban and a rural site in the North China Plain (NCP), a region with extensive anthropogenic emissions, during summer 2014. Saccharides, including anhydrosugars, monosaccharides, and sugar alcohols, were quantified. Profiles of saccharides in PM2.5 collected at urban and rural sites during the daytime and nighttime, nearby biomass burning, and without significant influence of biomass burning were investigated and compared. Contributions of biomass burning, biogenic aerosol associated with primary biological aerosol particles, and isoprene-derived secondary organic carbon (SOC) to total organic carbon were then estimated based on source-specific saccharide tracers. The results showed that concentrations of nearly all saccharides were higher at the rural site than at the urban site. Levoglucosan was the most abundant saccharide, followed by glycerol and glucose. Mass concentrations of source specific tracers and associated source contribution estimates indicated that the absolute and relative contributions of biomass burning were both much higher compared to fungal spore derived OC and isoprene SOC, with greater contributions observed at the rural site especially during nighttime. Our findings reveal that biogenic and biomass burning sources are non-negligible summertime contributors to atmospheric PM2.5 OC mass both at the rural site (up to 50%) and at the urban site (similar to 20%) in the NCP. (C) 2018 Elsevier B.V. All rights reserved.