Nitrate deposition to the Alaskan snowpack

Snowpack samples were collected from interior and arctic Alaska during March 1988 and analysed for pH, conductivity, NO₃⁻, SO₄²⁻ and other constituents. The mean snowpack NO₃⁻ and SO₄²⁻ concentrations in the interior Alaska snowpack were found to be 160 and 179 mg g⁻¹, respectively. The interior snowpack was observed to have concentrations and deposition fluxes of NO₃⁻ which are approximately 1.5 and 1–3 times, respectively, those observed in Greenland.

In the arctic samples, collected in the Sagavanirktok River Valley, wind-deposited loess substantially increases both pH and SO₄²⁻ concentrations in the snowpack. Snowpack nitrate in these samples is unaffected by the windborne loess and had a mean NO₃⁻ concentration of 688 ng g ⁻¹. The NO₃⁻ deposition flux in the Arctic is approximately two times that found in the interior snowpack.

The most plausible explanation for the elevated NO₃⁻ deposition flux is that the snowpack deposition is strongly influenced by the presence of the “arctic front”, a meteorological boundary which acts to contain the polluted, arctic air mass. Alternatively, local NO_x emissions on Alaska's arctic coast or substantial changes in the scavenging efficiencies may also influence the observe north-south gradient in NO₃⁻ concentrations in the snowpack.