A chemical comparison of snows from Mt Ruapehu, New Zealand and the Polar Plateau, East Antarctica

Abstract

The chemistry of surface, snowpit and ice core samples from Mt Ruapehu, New Zealand, was compared to surface snow samples from Mt Egmont-Taranaki, New Zealand, and to snowpit samples from the Polar Plateau, East Antarctica. Na⁺, K⁺, Ca²⁺, and Mg²⁺ were determined by atomic absorbtion spectrophotometry, and the anion contribution of Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, and SO₄²⁻ was determined by ion chromatography using a Dionex QIC II. Marine aerosols dominate in Antarctic snow, with significant enrichment of Ca from crustal sources, consistent with the location at the head of the Dry Valleys. On Mt Ruapehu, a marine background with superimposed volcanically derived concentrations of SO₄²⁻ is present in precipitation, with enrichment of all ions with phreatomagmatic and major phreatic activity, and enrichment of Ca²⁺ and SO₄²⁻ associated with minor phreatic activity. Na⁺ and Cl⁻ concentrations are significantly increased during southerly and westerly winds, but are also increased by volcanic activity. All New Zealand samples are enriched in K⁺ relative to bulk sea water, consistent with a crustal input. On Ruapehu, the dominant mechanisms of concentration are dry deposition and adsorbtion of gases for the volcanic components, and in-cloud scavenging of the marine components; while in Antarctica, the coastal region is dominated by scavenging and the Plateau is dominated by dry deposition and adsorbtion of gases.