Title: The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US

Abstract

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 themore » 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.« less

Authors:

Knote, C.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9105-9179"

Hodzic, A. ^[2]; Jimenez, J. L.  ^[3]

• Search DOE PAGES for author "Jimenez, J. L."
• Search DOE PAGES for ORCID "0000-0001-6203-1847"

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+ Show Author Affiliations

1. National Center for Atmospheric Research, Boulder, CO (United States). Atmospheric Chemistry Division; Ludwig Maximilian Univ., Munich (Germany). Meteorology Inst.
2. National Center for Atmospheric Research, Boulder, CO (United States). Atmospheric Chemistry Division
3. Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry

Publication Date:

Tue Jan 06 00:00:00 EST 2015

Research Org.:

National Center for Atmospheric Research (NCAR), Boulder, CO (United States)

Sponsoring Org.:

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 Org.:

National Atmospheric Deposition Program (NADP), Champaign, IL (United States)

OSTI Identifier:

1227788

Alternate Identifier(s):

OSTI ID: 1457228

Grant/Contract Number:  

SC0006711; SC0006035; CARB 11-305; NA13OAR4310063

Resource Type:

Published Article

Journal Name:

Atmospheric Chemistry and Physics (Online)

Additional Journal Information:

Journal Name: Atmospheric Chemistry and Physics (Online) Journal Volume: 15 Journal Issue: 1; Journal ID: ISSN 1680-7324

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY