Interaction of HNO₃ with water‐ice surfaces at temperatures of the free troposphere

Abstract

Abstract. The uptake of gas-phase HNO3 by water-ice films has been measured in a low-temperature, coated-wall flow tube under conditions where water-ice, and not a hydrate of nitric acid, is thermodynamically stable. It is observed that there-is uptake of HNO3 on the order of l•3x10 TM molecules per cm 2 of ice film on a short timescale, and a somewhat smaller uptake on a much longer timescale of 10's of minutes. The short timescale uptake is insensitive to the nitric acid partial pressure, varying by not more than a factor of two over a 20-fold variation in the partial pressure of HNO3 from 1.3 x 10 '7 to 3.1 x 10 '6 tort. This implies that the ice surface is saturated with HNO3 at these partial pressures. Also, the uptake is somewhat dependent on temperature over the range 208 to 248 K, with the largest uptake at the lowest temperarares. The uptake is largely irreversible, with only 20 • 25 % of the adsorbed HNO3 desorbing from the film when the exposure to gas-phase HNO3 is stopped. These experiments suggest that adsorption to cirrus cloud surfaces may be an important scavenging process of HNO3 in the troposphere.

Uptake of nitric acid by sub‐micron‐sized ice particles

“…However, it is only recently that the first quantitative studies of the scavenging ability of ice under tropospheric conditions were performed, by observing the loss of gas phase nitric acid onto thin films formed either by freezing liquid water [Abbatt, 1997] •Now at Department of Chemistry, University of Chicago, Chicago, IL, 60637.…”

Microbial Cell Retention in a Melting High Arctic Snowpack, Svalbard

“…When a snowflake grows in the atmosphere, or precipitates, it can absorb gases, aerosols, and supercooled droplets (Colbeck, 1981;Abbatt, 1997;Kuhn, 2001;Hoog et al, 2007). The large surface area of snowflakes leads to an efficient scavenging and removal of atmospheric pollutants (Chang, 1984;Barrie, 1991;Lei and Wania, 2004), which then end up in the snow cover.…”

Surface Snow, Firn and Ice Core Composition in Polar Areas in Relation to Atmospheric Aerosol and Gas Concentrations: Critical Aspects

“…Dominé and Thibert [52] suggested that HNO 3 is incorporated in ice growing by deposition of layers of a given thickness whose composition is determined by condensation kinetics. Solid diffusion is not a viable explanation for the large uptake of HNO 3 , due to its low diffusion coefficient and solubility in ice [69].…”