Abstract. This work investigates the individual and combined effects of temperature
and volatile organic compound precursor concentrations on the chemical
composition of particles formed in the dark ozonolysis of α-pinene.
All experiments were conducted in a 5 m3 Teflon chamber at an initial
ozone concentration of 100 ppb and initial α-pinene concentrations
of 10 and 50 ppb, respectively; at constant temperatures of 20, 0, or −15 ∘C; and at changing
temperatures (ramps) from −15 to 20 and from 20
to −15 ∘C. The chemical composition of the
particles was probed using a high-resolution time-of-flight aerosol mass
spectrometer (HR-ToF-AMS). A four-factor solution of a positive matrix factorization (PMF) analysis of
the combined HR-ToF-AMS data is presented. The PMF analysis and the
elemental composition analysis of individual experiments show that secondary
organic aerosol particles with the highest oxidation level are formed from
the lowest initial α-pinene concentration (10 ppb) and at the
highest temperature (20 ∘C). A higher initial α-pinene
concentration (50 ppb) and/or lower temperature (0 or −15 ∘C) results in a lower oxidation level of the molecules contained in
the particles. With respect to the carbon oxidation state, particles formed at 0 ∘C are more comparable to particles formed at −15 ∘C
than to those formed at 20 ∘C. A remarkable observation is that
changes in temperature during particle formation result in only minor
changes in the elemental composition of the particles. Thus, the temperature at
which aerosol particle formation is induced seems to be a critical
parameter for the particle elemental composition. Comparison of the HR-ToF-AMS-derived estimates of the content of organic
acids in the particles based on m/z 44 in the mass spectra show good
agreement with results from off-line molecular analysis of particle filter
samples collected from the same experiments. Higher temperatures are
associated with a decrease in the absolute mass concentrations of organic
acids (R-COOH) and organic acid functionalities (-COOH), while the organic
acid functionalities account for an increasing fraction of the measured
particle mass.
Kilometer-level glyoxal retrieval via satellite for anthropogenic volatile organic compound emission source and secondary organic aerosol formation identification
