The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US
[1];
[3]
- National Center for Atmospheric Research, Boulder, CO (United States). Atmospheric Chemistry Division; Ludwig Maximilian Univ., Munich (Germany). Meteorology Inst.
- National Center for Atmospheric Research, Boulder, CO (United States). Atmospheric Chemistry Division
- Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry
In this work, 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.
- Research Organization:
- National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF); California Air Resources Board (CARB), Sacramento, CA (United States); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
- Contributing Organization:
- National Atmospheric Deposition Program (NADP), Champaign, IL (United States)
- Grant/Contract Number:
- SC0006711; SC0006035; CARB 11-305; NA13OAR4310063
- OSTI ID:
- 1227788
- Alternate ID(s):
- OSTI ID: 1457228
- Journal Information:
- Atmospheric Chemistry and Physics (Online), Journal Name: Atmospheric Chemistry and Physics (Online) Vol. 15 Journal Issue: 1; ISSN 1680-7324
- Publisher:
- Copernicus Publications, EGUCopyright Statement
- Country of Publication:
- Germany
- Language:
- English
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