Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica
Antarctic ice core nitrate (NO<sub>3</sub><sup>−</sup>) can provide a unique record of the atmospheric reactive nitrogen cycle. However, the factors influencing the deposition and preservation of NO<sub>3</sub><sup>−</sup> at the ice sheet surface m...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-04-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/12/1177/2018/tc-12-1177-2018.pdf |
| Summary: | Antarctic ice core nitrate (NO<sub>3</sub><sup>−</sup>) can provide a unique
record of the atmospheric reactive nitrogen cycle. However, the factors
influencing the deposition and preservation of NO<sub>3</sub><sup>−</sup> at the ice
sheet surface must first be understood. Therefore, an intensive program of
snow and atmospheric sampling was made on a traverse from the coast to the
ice sheet summit, Dome A, East Antarctica. Snow samples in this observation
include 120 surface snow samples (top ∼ 3 cm), 20 snow pits
with depths of 150 to 300 cm, and 6 crystal ice samples (the topmost needle-like layer on Dome A plateau). The main purpose of this investigation is to
characterize the distribution pattern and preservation of NO<sub>3</sub><sup>−</sup>
concentrations in the snow in different environments. Results show that an
increasing trend of NO<sub>3</sub><sup>−</sup> concentrations with distance inland is
present in surface snow, and NO<sub>3</sub><sup>−</sup> is extremely enriched in the
topmost
crystal ice (with a maximum of 16.1 µeq L<sup>−1</sup>). NO<sub>3</sub><sup>−</sup>
concentration profiles for snow pits vary between coastal and inland sites.
On the coast, the deposited NO<sub>3</sub><sup>−</sup> was largely preserved, and the
archived NO<sub>3</sub><sup>−</sup> fluxes are dominated by snow accumulation. The
relationship between the archived NO<sub>3</sub><sup>−</sup> and snow accumulation
rate can be depicted well by a linear model, suggesting a homogeneity of
atmospheric NO<sub>3</sub><sup>−</sup> levels. It is estimated that dry deposition
contributes 27–44 % of the archived NO<sub>3</sub><sup>−</sup> fluxes, and the dry
deposition velocity and scavenging ratio for NO<sub>3</sub><sup>−</sup> were relatively
constant near the coast. Compared to the coast, the inland snow shows a
relatively weak correlation between archived NO<sub>3</sub><sup>−</sup> and snow
accumulation, and the archived NO<sub>3</sub><sup>−</sup> fluxes were more dependent on concentration. The relationship between NO<sub>3</sub><sup>−</sup> and coexisting ions
(nssSO<sub>4</sub><sup>2−</sup>, Na<sup>+</sup> and Cl<sup>−</sup>) was also investigated, and the
results show a correlation between nssSO<sub>4</sub><sup>2−</sup> (fine aerosol
particles) and NO<sub>3</sub><sup>−</sup> in surface snow, while the correlation between
NO<sub>3</sub><sup>−</sup> and Na<sup>+</sup> (mainly associated with coarse aerosol
particles) is not significant. In inland snow, there were no significant
relationships found between NO<sub>3</sub><sup>−</sup> and the coexisting ions,
suggesting a dominant role of NO<sub>3</sub><sup>−</sup> recycling in determining the
concentrations. |
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| ISSN: | 1994-0416 1994-0424 |