Pubs.GISS: Abstract of Fridlind and Jacobson 2000

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Fridlind and Jacobson 2000

Fridlind, A.M., and M.Z. Jacobson, 2000: A study of gas-aerosol equilibrium and aerosol pH in the remote marine boundary layer during the First Aerosol Characterization Experiment (ACE 1). J. Geophys. Res., 105, 17325-17340, doi:10.1029/2000JD900209.

A thermodynamic equilibrium model was applied to study the interactions of gas-phase NH₃, HNO₃, and HCl with size-resolved aerosols and estimate aerosol pH in the remote marine boundary layer during the First Aerosol Characterization Experiment (ACE 1). Analysis of model results and field measurements indicates that accumulation-mode aerosols were probably in equilibrium with NH₃, HNO₃, and HCl simultaneously. The largest coarse-mode aerosols did not appear to be in equilibrium with HNO₃, but may have been in equilibrium with NH₃ and HCl. The estimated pH of accumulation-mode aerosols was 0-2, a function primarily of the amount of sulfate relative to sea salt present in that mode. By contrast, the estimated equilibrium pH of coarse-mode aerosols was 2-5, a function primarily of relative humidity and gas-phase HCl. Prior to exposure to HCl, the estimated pH of fresh sea spray aerosols was 7-9, a function primarily of relative humidity. Sensitivity tests showed that the drying of aerosols during the sampling process may have volatilized up to 30% of NH₄⁺.