Index Geophysics

Parameterization of N2O5 reaction probabilities on the surface of particles containing ammonium, sulfate, and nitrate

A parameterization was developed for the heterogeneous reaction probability (<i>γ</i>) of N₂O₅ as a function of temperature, relative humidity (RH), particle composition, and phase state, for use in advanced air quality models. The reaction probabilities on aqueous NH₄HSO₄, (NH₄)₂SO₄, and NH₄NO₃ were modeled statistically using data and uncertainty values compiled from seven different laboratory studies. A separate regression model was fit to laboratory data for dry NH₄HSO₄ and (NH₄)₂SO₄ particles, yielding lower <i>γ</i> values than the corresponding aqueous parameterizations. The regression equations reproduced 80% of the laboratory data within a factor of two and 63% within a factor of 1.5. A fixed value was selected for <i>γ</i> on ice-containing particles based on a review of the literature. The combined parameterization was applied under atmospheric conditions representative of the eastern United States using 3-dimensional fields of temperature, RH, sulfate, nitrate, and ammonium. The resulting spatial distributions of <i>γ</i> were contrasted with three other parameterizations that have been applied in air quality models in the past and with atmospheric observational determinations of <i>γ</i>. Our equations lay the foundation for future research that will parameterize the suppression of <i>γ</i> when inorganic ammoniated particles are mixed or coated with organic material. Our analyses draw attention to a major uncertainty in the available laboratory data at high RH and highlight a critical need for future laboratory measurements of <i>γ</i> at low temperature and high RH to improve model simulations of N₂O₅ hydrolysis during wintertime conditions.

Davis, J. M.

Bhave, P. V.

Foley, K. M.

2018-01-15

Text

application/pdf

10.5194/acp-8-5295-2008

https://acp.copernicus.org/articles/8/5295/2008/

eISSN: 1680-7324

eng