Source characterization of highly oxidized multifunctional compounds in a boreal forest environment using positive matrix factorization
Other literature type
Rissanen, Matti P.
Canagaratna, Manjula R.
Häme, Silja A. K.
Prévôt, André S. H.
Worsnop, Douglas R.
(issn: 1680-7324, eissn: 1680-7324)
Highly oxidized multifunctional compounds (HOMs) have been demonstrated to
be important for atmospheric secondary organic aerosols (SOA) and new-particle formation (NPF), yet it remains unclear which the main atmospheric
HOM formation pathways are. In this study, a nitrate-ion-based chemical
ionization atmospheric-pressure-interface time-of-flight mass spectrometer
(CI-APi-TOF) was deployed to measure HOMs in the boreal forest in
Hyytiälä, southern Finland. Positive matrix factorization (PMF) was
applied to separate the detected HOM species into several factors, relating
these “factors” to plausible formation pathways. PMF was performed with a
revised error estimation derived from laboratory data, which agrees well
with an estimate based on ambient data. Three factors explained the majority
(> 95 %) of the data variation, but the optimal solution found
six factors, including two nighttime factors, three daytime factors, and a
transport factor. One nighttime factor is almost identical to laboratory
spectra generated from monoterpene ozonolysis, while the second likely
represents monoterpene oxidation initiated by NO<sub>3</sub>. The exact chemical
processes forming the different daytime factors remain unclear, but they all
have clearly distinct diurnal profiles, very likely related to monoterpene
oxidation with a strong influence from NO, presumably through its effect on
peroxy radical (RO<sub>2</sub>) chemistry. Apart from these five “local”
factors, the sixth factor is interpreted as a transport related factor.
These findings improve our understanding of HOM production by confirming
current knowledge and inspiring future research directions and provide new
perspectives on using factorization methods to understand short-lived