Experimental Protocol for the Chemical Analysis of Snow, Firn and Ice Cores

Abstract

The methods used for the chemical analysis of polar snow, firn and ice samples are described, reflecting the high level of care required throughout all the experimental processes, from field sampling to analytical measurement in the laboratory.

Shallow snow or firn samples can be taken directly in pits or trenches whereas deep firn and ice sampling requires drilling devices, generally heavily contaminating the surface of the cores retrieved. A procedure is described for sub-sampling and recoring firn and ice cores in clean rooms to increase the reliability of results. Only the case of major soluble ions (H⁺ Na⁺ K⁺ Mg⁺⁺ Ca⁺⁺ SO₄ = Cl^- and NO₃ ^-) is dealt with, the case of minor constituents needing much more sophisticated methods. The concentrations to be measured are generally in the range 1–100 ppb (ng g^-1). All these ions (except H⁺) can be measured by ion chromatography. Experimental tests conducted in our laboratory are described in detail and the most favorable working conditions for obtaining a balanced ion budget of polar precipitation are selected. These analytical procedures can also be applied to the chemical investigation of snow deposited in winter in mid-latitude mountainous locations.