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| Titel |
Examining the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol formation during the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee ground site |
| VerfasserIn |
S. H. Budisulistiorini, X. Li, S. T. Bairai, J. Renfro, Y. Liu, Y. J. Liu, K. A. McKinney, S. T. Martin, V. F. McNeill, H. O. T. Pye, A. Nenes, M. E. Neff, E. A. Stone, S. Mueller, C. Knote, S. L. Shaw, Z. Zhang, A. Gold, J. D. Surratt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 15 ; Nr. 15, no. 15 (2015-08-13), S.8871-8888 |
| Datensatznummer |
250119960
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| Publikation (Nr.) |
 copernicus.org/acp-15-8871-2015.pdf |
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| Zusammenfassung |
| A suite of offline and real-time gas- and particle-phase measurements was
deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant and
Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on
isoprene-derived secondary organic aerosol (SOA) formation. High- and
low-time-resolution PM2.5 samples were collected for analysis of known
tracer compounds in isoprene-derived SOA by gas chromatography/electron
ionization-mass spectrometry (GC/EI-MS) and ultra performance liquid
chromatography/diode array detection-electrospray ionization-high-resolution
quadrupole time-of-flight mass spectrometry (UPLC/DAD-ESI-HR-QTOFMS). Source
apportionment of the organic aerosol (OA) was determined by positive matrix
factorization (PMF) analysis of mass spectrometric data acquired on an
Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Campaign average mass
concentrations of the sum of quantified isoprene-derived SOA tracers
contributed to ~ 9 % (up to 28 %) of the total OA mass,
with isoprene-epoxydiol (IEPOX) chemistry accounting for ~ 97 % of the quantified tracers. PMF analysis resolved a factor with a
profile similar to the IEPOX-OA factor resolved in an Atlanta study and was
therefore designated IEPOX-OA. This factor was strongly correlated
(r2 > 0.7) with 2-methyltetrols, C5-alkene triols,
IEPOX-derived organosulfates, and dimers of organosulfates, confirming the
role of IEPOX chemistry as the source. On average, IEPOX-derived SOA tracer
mass was ~ 26 % (up to 49 %) of the IEPOX-OA factor mass,
which accounted for 32 % of the total OA. A low-volatility oxygenated
organic aerosol (LV-OOA) and an oxidized factor with a profile similar to
91Fac observed in areas where emissions are biogenic-dominated were also
resolved by PMF analysis, whereas no primary organic aerosol (POA) sources
could be resolved. These findings were consistent with low levels of primary
pollutants, such as nitric oxide (NO ~ 0.03 ppb), carbon
monoxide (CO ~ 116 ppb), and black carbon (BC ~ 0.2 μg m−3). Particle-phase sulfate is fairly correlated
(r2 ~ 0.3) with both methacrylic acid epoxide
(MAE)/hydroxymethyl-methyl-α-lactone (HMML)- (henceforth called
methacrolein (MACR)-derived SOA tracers) and IEPOX-derived SOA tracers, and
more strongly correlated (r2 ~ 0.6) with the IEPOX-OA
factor, in sum suggesting an important role of sulfate in isoprene SOA
formation. Moderate correlation between the MACR-derived SOA tracer
2-methylglyceric acid with sum of reactive and reservoir nitrogen oxides
(NOy; r2 = 0.38) and nitrate (r2 = 0.45) indicates the
potential influence of anthropogenic emissions through long-range transport.
Despite the lack of a clear association of IEPOX-OA with locally estimated
aerosol acidity and liquid water content (LWC), box model calculations of
IEPOX uptake using the simpleGAMMA model, accounting for the role of acidity
and aerosol water, predicted the abundance of the IEPOX-derived SOA tracers
2-methyltetrols and the corresponding sulfates with good accuracy (r2
~ 0.5 and ~ 0.7, respectively). The modeling and
data combined suggest an anthropogenic influence on isoprene-derived SOA
formation through acid-catalyzed heterogeneous chemistry of IEPOX in the
southeastern US. However, it appears that this process was not limited by
aerosol acidity or LWC at Look Rock during SOAS. Future studies should
further explore the extent to which acidity and LWC as well as aerosol
viscosity and morphology becomes a limiting factor of IEPOX-derived SOA, and
their modulation by anthropogenic emissions. |
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