Abstract. Antarctic ice core nitrate (NO3-) can provide a unique
record of the atmospheric reactive nitrogen cycle. However, the factors
influencing the deposition and preservation of NO3- 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 NO3-
concentrations in the snow in different environments. Results show that an
increasing trend of NO3- concentrations with distance inland is
present in surface snow, and NO3- is extremely enriched in the
topmost
crystal ice (with a maximum of 16.1 µeq L−1). NO3-
concentration profiles for snow pits vary between coastal and inland sites.
On the coast, the deposited NO3- was largely preserved, and the
archived NO3- fluxes are dominated by snow accumulation. The
relationship between the archived NO3- and snow accumulation
rate can be depicted well by a linear model, suggesting a homogeneity of
atmospheric NO3- levels. It is estimated that dry deposition
contributes 27–44 % of the archived NO3- fluxes, and the dry
deposition velocity and scavenging ratio for NO3- were relatively
constant near the coast. Compared to the coast, the inland snow shows a
relatively weak correlation between archived NO3- and snow
accumulation, and the archived NO3- fluxes were more dependent on concentration. The relationship between NO3- and coexisting ions
(nssSO42-, Na+ and Cl−) was also investigated, and the
results show a correlation between nssSO42- (fine aerosol
particles) and NO3- in surface snow, while the correlation between
NO3- and Na+ (mainly associated with coarse aerosol
particles) is not significant. In inland snow, there were no significant
relationships found between NO3- and the coexisting ions,
suggesting a dominant role of NO3- recycling in determining the
concentrations.
Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica