In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 21 ( 2022-11-04), p. 14147-14175
Kurzfassung:
Abstract. A comprehensive chamber investigation of photochemical
secondary organic aerosol (SOA) formation and transformation in mixtures of
anthropogenic (o-cresol) and biogenic (α-pinene and isoprene)
volatile organic compound (VOC) precursors in the presence of NOx and
inorganic seed particles was conducted. To enable direct comparison across
systems, the initial concentration (hence reactivity) of the systems towards
the dominant OH oxidant was adjusted. Comparing experiments conducted in
single-precursor systems at various initial reactivity levels (referenced to
a nominal base case VOC concentration, e.g. halving the initial
concentration for a 1/2 initial reactivity experiment) as well as their
binary and ternary mixtures, we show that the molecular interactions from
the mixing of the precursors can be investigated and discuss challenges in
their interpretation. The observed average SOA particle mass yields (the
organic particle mass produced for a mass of VOC consumed) in descending
order were found for the following systems: α-pinene (32 ± 7 %), α-pinene–o-cresol (28 ± 9 %), α-pinene at 1/2
initial reactivity (21 ± 5 %), α-pinene–isoprene (16 ± 1 %), α-pinene at 1/3 initial reactivity (15 ± 4 %), o-cresol
(13 ± 3 %), α-pinene–o-cresol–isoprene (11 ± 4 %),
o-cresol at 1/2 initial reactivity (11 ± 3 %), o-cresol–isoprene (6 ± 2 %), and isoprene (0 ± 0 %). We find a
clear suppression of the SOA mass yield from α-pinene when it is
mixed with isoprene, whilst no suppression or enhancement of SOA particle
yield from o-cresol was found when it was similarly mixed with isoprene. The
α-pinene–o-cresol system yield appeared to be increased compared to
that calculated based on the additivity, whilst in the α-pinene–o-cresol–isoprene system the measured and predicted yields were comparable.
However, in mixtures in which more than one precursor contributes to the SOA
particle mass it is unclear whether changes in the SOA formation potential
are attributable to physical or chemical interactions, since the reference
basis for the comparison is complex. Online and offline chemical composition
as well as SOA particle volatility, water uptake, and “phase” behaviour
measurements that were used to interpret the SOA formation and behaviour are
introduced and detailed elsewhere.
Materialart:
Online-Ressource
ISSN:
1680-7324
DOI:
10.5194/acp-22-14147-2022
DOI:
10.5194/acp-22-14147-2022-supplement
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2022
ZDB Id:
2092549-9
ZDB Id:
2069847-1
