Characterization of saccharides in size-fractionated ambient particulate matter and aerosol sources: the contribution of primary biological aerosol particles (PBAPs) and soil to ambient particulate matter.

Size-fractionated (equivalent to ambient PM2.5 and PM10) local soil, plant, and spore samples were collected in the Sonoran Desert near Phoenix, AZ and measured for saccharide content with the goal of characterizing ambient particulate matter sources including soil and primary biological aerosol particles (PBAPs) from plants and fungi. Different saccharide compositions were observed among soil, plant, and spore samples and between PM2.5 and PM10 fractions. The total measured nonlevoglucosan saccharide content relative to PM mass in ambient aerosols collected in a Phoenix suburb (Higley) was much higher compared to the local soil samples but much lower compared to the PBAP. The enrichment of saccharides from two saccharide-dominated PM source factors resolved by a positive matrix factorization model is also higher than the saccharide content in the size-fractionated local soil samples, but lower than that measured in the size-segregated PBAP samples. This indicates that ambient concentration of particulate saccharides at Higley was dominated by contributions from PBAPs directly injected into the atmosphere from plants and spores rather than from soil and associated biota. Our results also suggest the contribution to the fine size fraction of ambient PM from the primary biologically derived sources may be greater than previously acknowledged.