Major Ion Content of Aerosols from Denali Base Camp during Summer 2013

Abstract:

Aerosol samples were collected on Teflon filters at a site up-glacier from Denali Base Camp (2380 m) in Denali National Park, Alaska during May and June of 2013 using an autonomous aerosol sampler powered by solar panels and batteries. The samples were analyzed for major ions via ion chromatography. Surface and fresh snow samples were also collected over the same time period and analyzed for major ions. Ion concentrations in the aerosol samples are completely dominated by NH₄⁺ (mean concentration of 6.6 nmol/m3) and SO₄⁼ (mean concentration of 4.0 nmol/m3). Overall, the ion burden in aerosol samples from Denali Base Camp was much lower compared to aerosol samples collected from the Denali National Park and Trapper Creek IMPROVE sites over the same time period.

In contrast to the aerosol chemistry, the snow chemistry is more balanced, with NH₄⁺, Ca²⁺, and Na⁺ dominating the cation concentrations and NO₃^-, Cl^-, and SO₄⁼ dominating the anion concentrations. The higher levels of Ca²⁺, Na⁺, and Cl^- in the snow (relative to NH₄⁺ and SO₄⁼) compared to relative concentrations in the aerosol samples suggest that dry deposition of sea salt and dust are important contributors to the major ion signals preserved in the snow. This has important ramifications for improving our understanding of the reconstruction of North Pacific climate variability and change from glaciochemical records currently being developed from the 208 m ice cores recovered from the Mt. Hunter plateau (3900 m) during the summer of 2013.