Size-Resolved Identification, Characterization, and Quantification of Primary Biological Organic Aerosol at a European Rural Site

Primary biological organic aerosols
(PBOA) represent a major component of the coarse organic matter (OMCOARSE, aerodynamic diameter > 2.5 μm). Although this
fraction affects human health and the climate, its quantification
and chemical characterization currently remain elusive. We present
the first quantification of the entire PBOACOARSE mass and its main
sources by analyzing size-segregated filter samples collected during
the summer and winter at the rural site of Payerne (Switzerland),
representing a continental Europe background environment. The size-segregated
water-soluble OM was analyzed by a newly developed offline aerosol
mass spectrometric technique (AMS). Collected spectra were analyzed
by three-dimensional positive matrix factorization (3D-PMF), showing
that PBOA represented the main OMCOARSE source during summer
and its contribution to PM10 was comparable to that of
secondary organic aerosol. We found substantial cellulose contributions
to OMCOARSE, which in combination with gas chromatography
mass spectrometry molecular markers quantification, underlined the
predominance of plant debris. Quantitative polymerase chain reaction
(qPCR) analysis instead revealed that the sum of bacterial and fungal
spores mass represented only a minor OMCOARSE fraction
(<0.1%). X-ray photoelectron spectroscopic (XPS) analysis of C
and N binding energies throughout the size fractions revealed an organic
N increase in the PM10 compared to PM1 consistent
with AMS observations.