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| Titel |
The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US |
| VerfasserIn |
C. Knote, A. Hodzic, J. L. Jimenez |
| 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. 1 ; Nr. 15, no. 1 (2015-01-06), S.1-18 |
| Datensatznummer |
250119282
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| Publikation (Nr.) |
 copernicus.org/acp-15-1-2015.pdf |
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| Zusammenfassung |
| The effect of dry and wet deposition of semi-volatile organic
compounds (SVOCs) in the gas phase on the concentrations of secondary
organic aerosol (SOA) is reassessed using recently derived water
solubility information. The water solubility of SVOCs was
implemented as a function of their volatility distribution within
the WRF-Chem regional chemistry transport model, and simulations
were carried out over the continental United States for the year
2010. Results show that including dry and wet removal of gas-phase
SVOCs reduces annual average surface concentrations of anthropogenic
and biogenic SOA by 48 and 63% respectively over the
continental US. Dry deposition of gas-phase SVOCs is found to be more
effective than wet deposition in reducing SOA concentrations
(−40 vs. −8% for anthropogenics, and −52
vs. −11% for biogenics). Reductions for biogenic SOA are
found to be higher due to the higher water solubility of biogenic
SVOCs. The majority of the total mass of SVOC + SOA is actually
deposited via the gas phase (61% for anthropogenics and 76%
for biogenics). Results are sensitive to assumptions
made in the dry deposition scheme, but gas-phase deposition of SVOCs remains
crucial even under conservative estimates. Considering reactivity of gas-phase
SVOCs in the dry deposition scheme was found to be negligible. Further
sensitivity studies where we reduce the volatility of organic matter
show that consideration of gas-phase
SVOC removal still reduces average SOA concentrations by 31% on
average. We consider this a lower bound for the effect of gas-phase
SVOC removal on SOA concentrations. A saturation
effect is observed for Henry's law constants above
108 M atm−1, suggesting an upper bound of
reductions in surface level SOA concentrations by 60% through
removal of gas-phase SVOCs.
Other models that do not consider dry and wet removal of gas-phase SVOCs would
hence overestimate SOA concentrations by roughly 50%. Assumptions
about the water solubility of SVOCs made in some current modeling
systems (H* = H* (CH3COOH);
H* = 105 M atm−1; H* = H* (HNO3))
still lead to an overestimation of
35%/25%/10% compared to our best estimate. |
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