Ion elution through shallow homogeneous snow

Abstract

Controlled melting of snowpacks in the laboratory demonstrates the importance of the initial distribution of chemical species within the pack (mesoscale) and within the snow grains (microscale) to the timing and relative concentrations of meltwater released from the base of the pack. Acid and salt tracers were applied to homogeneous snow in order to investigate these effects. Species deposited near the top of the pack eluted out considerably before those more uniformly distributed with depth. Also, about 80% of the salts dosed at the top of a 0.4‐m pack were removed in the first 20% of the meltwater, versus 70% of a salt dosed at middepth. Both the top and middepth tracers were present in the first fractions of meltwater draining from the pack, however, indicating that there is partial mixing of percolating meltwater with solutes in an immobile surface phase on grains deeper in the pack. Concentration of species on the outside of grains by seasonal metamorphism and on the outside of multigrain particles and clusters during melt freeze will enhance their early removal. Different ions that were present in the snow with the same mesoscale and microscale conditions prior to melt came out at the same relative concentrations; i.e., they did not exhibit preferential elution.