Article

Surprisingly small HONO emissions from snow surfaces at Browning Pass, Antarctica

Atmospheric Chemistry and Physics 01/2006; DOI: 10.5194/acp-6-2569-2006
Source: DOAJ

ABSTRACT Measured Fluxes of nitrous acid at Browning Pass, Antarctica were very low, despite conditions that are generally understood as favorable for HONO emissions, including: acidic snow surfaces, an abundance of NO3- anions in the snow surface, and abundant UV light for NO3- photolysis. Photochemical modeling suggests noon time HONO fluxes of 5–10 nmol m-2 h-1; the measured fluxes, however, were close to zero throughout the campaign. The location and state of NO3- in snow is crucial to its reactivity. The analysis of soluble mineral ions in snow reveals that the NO3- ion is probably present in aged snows as NaNO3. This is peculiar to our study site, and we suggest that this may affect the photochemical reactivity of NO3-, by preventing the release of products, or providing a reactive medium for newly formed HONO. In fresh snow, the NO3- ion is probably present as dissolved or adsorbed HNO3 and yet, no HONO emissions were observed. We speculate that HONO formation from NO3- photolysis may involve electron transfer reactions of NO2 from photosensitized organics and that fresh snows at our site had insufficient concentrations of adequate organic compounds to favor this reaction.

0 Bookmarks
 · 
71 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An unknown fraction of mercury that is deposited onto the cryosphere is emitted back to the atmosphere. Since mercury that enters the meltwater may be converted to highly toxic bioaccumulating methylmercury, it is important to understand the physical and chemical processes that control the ultimate fate of mercury in the cryosphere. In this study, we review deposition mechanisms as well as processes whereby mercury is lost from surface snow. We then discuss redox reactions involving cryospheric mercury. We address the conditions under which reduction and oxidation occur, the stabilizing effect of halides, and the reducibility of reactive gaseous mercury versus mercury associated with particles. We discuss physical processes including the aging of the snowpack, the penetration of insolation through the cryosphere, the vertical motion of gaseous elemental mercury molecules through the cryosphere, the melting of snowpacks, and the loss of mercury from snowpacks during snowmelt both to the atmosphere and with the meltwater's ionic pulse. These physicochemical processes are universally applicable. Variations in the behavior of cryospheric mercury between open high-latitude, open high-altitude, and forested regions, which are caused by differing environmental conditions, are also discussed. Finally, we review observed concentrations of mercury in surface snow, seasonal snowpacks, meltwater, and long-term cryospheric records. The information presented here can be used to develop a parameterization of the behavior of cryospheric mercury that is dynamically linked to environmental variables.
    Journal of Geophysical Research 01/2011; 116. · 3.17 Impact Factor
  • Source
    11/2011: pages 4 1–4 58; , ISBN: 978-82-7971-071-4
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Photochemical reactions in snow can have an important impact on the composition of the atmosphere over snow-covered areas as well as on the composition of the snow itself. One of the major photochemical processes is the photolysis of nitrate leading to the formation of volatile nitrogen compounds. We report nitrite concentrations determined together with nitrate and hydrogen peroxide in surface snow collected at the coastal site of Barrow, Alaska. The results demonstrate that nitrite likely plays a significant role as a precursor for reactive hydroxyl radicals as well as volatile nitrogen oxides in the snow. Pollution events leading to high concentrations of nitrous acid in the atmosphere contributed to an observed increase in nitrite in the surface snow layer during nighttime. Observed daytime nitrite concentrations are much higher than values predicted from steady-state concentrations based on photolysis of nitrate and nitrite indicating that we do not fully understand the production of nitrite and nitrous acid in snow. The discrepancy between observed and expected nitrite concentrations is probably due to a combination of factors, including an incomplete understanding of the reactive environment and chemical processes in snow, and a lack of consideration of the vertical structure of snow.
    Environmental Science & Technology 11/2013; · 5.26 Impact Factor

Full-text (2 Sources)

View
22 Downloads
Available from
May 15, 2014