Atmosphere–snow interaction by a comparison between aerosol and uppermost snow-layers composition at Dome C, East Antarctica

Abstract

The study of aerosol composition and air–snow exchange processes is relevant to the reconstruction of past atmosphere composition from ice cores. For this purpose, aerosol samples, superficial snow layers and firn samples from snow pits were collected at Dome Concordia station, East Antarctica, during the 2000/01 summer field season. The aerosol was collected in a ‘coarse’ and a ‘fine’ fraction, roughly separated from each other by a stacked filter system (5.0 and 0.4 μm). Atomic Force Microscopy (AFM) direct measurements on the fine fraction showed that 72% of surface size distribution ranges from 1.0 x 105 to 1.2 x 106 nm2. Assuming a spherical model, the volume size distribution of particles smaller than 5.0 μm shows a mode in the radius range 0.2–0.6 μm. Ion chromatographic (IC) measurements of selected chemical components allowed calculation of the ionic balance of the two size fractions. The fine fraction is dominant, representing 86% of the total ionic budget, and it is characterized by high content of sulphate and acidity. Principal component analysis (PCA) identified sea-spray and biogenic aerosol sources and showed some particulars of the transport and depositional processes of some chemical components (Ca2+, MSA, nssSO42–). Comparative analysis of aerosol, surface hoar and superficial snow showed differences in chemical composition: nitrate and chloride exhibit very high concentrations in the uppermost snow layers and in the surface hoar, and low values in the aerosol. This evidence demonstrates that nitrate and chloride are mainly in gas phase at Dome C and they can be caught on the snow and hoar surface through dry deposition and adsorption processes.

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

“…At a given temperature, k eff H increases by an order of magnitude between pH 5 and 6.5 (Fig. B3a), the typical range of pH in natural snow (Udisti et al, 2004). While at a given pH, k eff H decreases by 2 orders of magnitude between −40 and 0 • C (Fig.…”

“…B3b). Note that the range of pH measured by Udisti et al (2004) is the pH of the melted sample, which might be different from the pH of the liquid fraction of the snow grain not observable by current measurement techniques.…”

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

“…Udisti et al [7] collected atmospheric aerosol, superficial snow layers and firn samples from snow pits at Dome Concordia station during the 2000/2001 summer field season. Comparative analysis of aerosol, surface hoar and surface snow showed differences in chemical composition.…”

“…concentrations in snow and in air are sometimes related and sometimes not [7] [9] [16] [17] [19] [20]. Published papers frequently compared ion concentration (soluble and/or insoluble) in snow and aerosol, neglecting to discuss the fact that snow could also scavenge chemical compounds in the gas phase.…”

Aerosol and snow transfer processes: An investigation on the behavior of water-soluble organic compounds and ionic species

“…At Dome C on the Antarctic plateau, it was demonstrated that nitrate and chloride can be caught by the surface snow through dry deposition and adsorption processes (Udisti et al, 2004). The interactions of carboxylic acid at the air-snow interface has been studied in the Arctic (Narukawa et al, 2002), and underlined the compositional difference between aerosol and snow samples.…”