In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 18, No. 16 ( 2018-08-16), p. 11663-11682
Abstract:
Abstract. Nighttime reaction of nitrate radicals (NO3) with biogenic volatile
organic compounds (BVOC) has been proposed as a potentially important but
also highly uncertain source of secondary organic aerosol (SOA). The
southeastern United States has both high BVOC and nitrogen oxide
(NOx) emissions, resulting in a large model-predicted
NO3-BVOC source of SOA. Coal-fired power plants in this region
constitute substantial NOx emissions point sources into a
nighttime atmosphere characterized by high regionally widespread
concentrations of isoprene. In this paper, we exploit nighttime aircraft
observations of these power plant plumes, in which NO3 radicals
rapidly remove isoprene, to obtain field-based estimates of the secondary
organic aerosol yield from NO3 + isoprene. Observed in-plume
increases in nitrate aerosol are consistent with organic nitrate aerosol
production from NO3 + isoprene, and these are used to determine
molar SOA yields, for which the average over nine plumes is 9 % (±5 %). Corresponding mass yields depend on the assumed molecular formula
for isoprene-NO3-SOA, but the average over nine plumes is 27 %
(±14 %), on average larger than those previously measured in chamber
studies (12 %–14 % mass yield as ΔOA ∕ ΔVOC after
oxidation of both double bonds). Yields are larger for longer plume ages.
This suggests that ambient aging processes lead more effectively to
condensable material than typical chamber conditions allow. We discuss
potential mechanistic explanations for this difference, including longer
ambient peroxy radical lifetimes and heterogeneous reactions of
NO3-isoprene gas phase products. More in-depth studies are needed to
better understand the aerosol yield and oxidation mechanism of NO3
radical + isoprene, a coupled anthropogenic–biogenic source of SOA that
may be regionally significant.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-18-11663-2018
DOI:
10.5194/acp-18-11663-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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