Abstract. Kraków is routinely affected by very high air pollution
levels, especially during the winter months. Although a lot of effort has
been made to characterize ambient aerosol, there is a lack of online
and long-term measurements of non-refractory aerosol. Our measurements at
the AGH University of Science and Technology provide the online long-term chemical composition of ambient
submicron particulate matter (PM1) between January 2018 and April 2019.
Here we report the chemical characterization of non-refractory submicron
aerosol and source apportionment of the organic fraction by positive matrix
factorization (PMF). In contrast to other long-term source apportionment
studies, we let a small PMF window roll over the dataset instead of
performing PMF over the full dataset or on separate seasons. In this way,
the seasonal variation in the source profiles can be captured. The
uncertainties in the PMF solutions are addressed by the bootstrap resampling
strategy and the random a-value approach for constrained factors. We observe clear seasonal patterns in the concentration and composition of
PM1, with high concentrations during the winter months and lower
concentrations during the summer months. Organics are the dominant species
throughout the campaign. Five organic aerosol (OA) factors are resolved, of
which three are of a primary nature (hydrocarbon-like OA (HOA), biomass
burning OA (BBOA) and coal combustion OA (CCOA)) and two are of a secondary
nature (more oxidized oxygenated OA (MO-OOA) and less oxidized oxygenated OA
(LO-OOA)). While HOA contributes on average 8.6 % ± 2.3 %
throughout the campaign, the solid-fuel-combustion-related BBOA and CCOA
show a clear seasonal trend with average contributions of 10.4 % ± 2.7 % and 14.1 %, ±2.1 %, respectively. Not only BBOA but
also CCOA is associated with residential heating because of the pronounced
yearly cycle where the highest contributions are observed during wintertime.
Throughout the campaign, the OOA can be separated into MO-OOA and LO-OOA
with average contributions of 38.4 % ± 8.4 % and 28.5 % ± 11.2 %, respectively.