Fluxes of nitrates between snow surfaces and the atmosphere in the European high Arctic

Abstract

Abstract. Measurements of atmospheric and snow mixing ratios of nitrates and nitrites and their fluxes above the snow surface were made during two intensive campaigns during spring time 2001 at Ny-Ålesund, Svalbard as part of the EU project "The NItrogen Cycle and Effects on the oxidation of atmospheric trace species at high latitudes" (NICE).At this coastal site close to the unseasonably unfrozen fjord, of the measured nitrogen species, only HNO 3 showed a significant flux on to the snow surface; a mean deposition of −8.7 nmol h −1 m −2 was observed in late April / early May 2001. These fluxes may be due to the reaction of HNO 3 with sea salt, and especially NaCl, or may be simply uptake of HNO 3 by ice, which is alkaline because of the sea salt in our marine environment. During snowfall periods dry deposition of HNO 3 may contribute up to 10% of the N budget in the snow; however, the main source for N is wet deposition in falling snow.The surface snow at Ny-Ålesund showed very complex stratigraphy; the NO − 3 mixing ratio in snow varied between 65 and 520 ng g −1 , the total NO − 3 content of the snowpack was on the order of 2700 ng cm −2 . In comparison the atmospheric boundary layer column showed a NO − 3 content of only 8 ng cm −2 . The limited exchange, however, between the snow and the atmosphere was attributed to low mobility of NO − 3 in the observed snow. Contrary to other Arctic sites (i.e. Alert, Nunavut or Summit, Greenland) deposition of sea salt and crustal aerosols in this marine environment made the surface snow alkaline; snow NO − 3 was associated with heavier cations and was not readily available for physical exchange or photochemical reactions.

Deposition of atmospheric nitrous acid on alkaline snow surfaces

“…The HONO emission fluxes were minute and well below the uncertainty of the methods involved; on only two occasions emission fluxes of up to 20 nmol m À2 h À1 from the snow surface were seen for up to 6 hours length. We will not further discuss the emission fluxes, since we believe that two small events do not warrant extensive discussion, and that the basic photochemical emission mechanism seems to be understood [Beine et al, 2003].…”

“…[10] 3D measurements previously conducted for a 25-day period in late spring at the same heights and over the same surface type at Ny-Å lesund, Svalbard [Beine et al, 2003] allowed to parameterize the vertical wind speed as a function of the friction velocity under near-neutral atmospheric stability. 1 Thus, at MTC, the Monin Obukhov length (L), required to calculate HONO fluxes, was not measured directly but obtained through iterative computation.…”

“…envelope around the chemical measurements to determine the HONO fluxes. The derivation of HONO fluxes from the gradient technique [Sozzi et al, 1998] is fully described by Beine et al [2003]. Because 3D wind speed measurements were not available at the site, the vertical wind speed component was parameterized utilizing a similarity procedure.…”

Modelling the physical multiphase interactions of HNO<sub>3</sub> between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

“…associated with Na + , Ca 2+ or Mg 2+ (Beine et al, 2003). An increase in sea salt aerosol concentration can shift gaseous HNO 3 to particle phase (i.e.…”

Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland

“…The flux-gradient method was used to estimate microbial fluxes from concentrations measured with the Burkard samplers. This methodology has been widely used to measure atmospheric fluxes of different scalars such as hydrogen (Meredith et al, 2014), nitrates and nitrogen compounds (Beine et al, 2003;Griffith and Galle, 2000;Taylor et al, 1999), mercury (Edwards et al, 2005;Fritsche et al, 2008;Lindberg et al, 1995), and particulate matter (Bonifacio et al, 2013;Kjelgaard et al, 2004;Park et al, 2011;Sow et al, 2009). The method follows the Monin-Obukhov similarity theory (Monin and Obukhov, 1954) and therefore assumes that in the atmospheric surface layer the flux of a certain scalar is a function of the gradient of the scalar measured at different heights, the heights themselves (z i ), and a transport velocity that is dependent on atmospheric turbulence and stability (a more detailed description of the methodology is provided in the Supplement).…”