Snow-to-air exchanges of mercury in an Arctic seasonal snow pack in Ny-Ã lesund, Svalbard

In the snow pack which is seasonal and about 40 cm depth above permafrost, Hg is involved in both production and incorporation processes. The incorporation was evaluated to ∼5-40 pg m2 h. Outside of AMDE periods, Hg flux from the snow surface to the atmosphere was the consequence of GEM production in the air of snow and was about ∼15-50 ng m−2 h−1, with a contribution of deeper snow layers evaluated to ∼0.3-6.5 ng m−2 h−1. The major part of GEM production is then mainly a surface phenomenon. The internal production of GEM was largely increasing when snow temperatures were close to melting, indicating a chemical process occurring in the quasi-liquid layer at the surface of snow grains.