Abstract

In the polar regions, the usual OH radical formation pathway (ozone photolysis and reaction of O(1D) with H2O ) is limited by the low water vapour concentration. However, gases emitted from the snowpack can be pre-cursors of HOx radicals and ozone, thereby controlling the oxidising capacity of the lower atmosphere above remote snow-covered regions. One such gas is nitrous acid (HONO) which is photolyzed to produce OH. Previous studies of HONO in the polar boundary layer and snowpack interstitial air suggest a photolytic snowpack source but the exact mechanism for HONO production is poorly understood; photochemical models of HONO sources and sinks often cannot be reconciled with the measured HONO concentrations. We investigated the net HONO flux density above snow in the Clean Air Sector at Halley VI Research Station in coastal Antarctica during austral summer 2021-22. Amount fraction measurements of HONO in ambient air will be presented, as well as measurements of the HONO flux density between the snow and atmosphere. The potential snowpack reactions driving this HONO release, and the implications of these measurements for the HOx budget, will be discussed. These findings help further our understanding of the atmospheric budget of reactive nitrogen and highlight the significant effects snow surfaces can have on the atmospheric chemistry in the boundary layer above.

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Topic: CAS Seminar: Amelia Bond, 6 June (2:00 PM) Time: Jun 6, 2023 02:00 PM London

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