Transport and Chemodynamics of Organic Micropollutants and Ions during Snowmelt

Abstract

By means of laboratory experiments and field measurements we investigated the chemodynamics and transport behaviour of organic micropollutants and inorganic ions in melting snowpacks. Dissolved substances (e.g. ions) were released from the snowpack by convection and diffusion within the melt water. Substances which were adsorbed onto particles (e.g. PAH) were not desorbed to a significant degree. Moving particles were generally filtered out within the snowpack and, therefore, adsorbed substances were hardly leached by this way of transport. Frequent melt-freeze cycles and a deep snowpack lead to an enrichment of dissolved substances in the first melt water fractions and of substances adsorbed onto particles in the final fractions. A different macroscopic and microscopic spatial variation of ions within the snowpack results in different elution patterns during the snow melt. Since the PAH are predominantly adsorbed onto particles, approximately 90% of all PAH of a snow column were eluted with the last 20% of water during the snow melt. PAH with a high partition coefficient kow (e.g. benzo(a) pyrene, benzo(ghi)perylene) exhibited a stronger enrichment than fluoranthene with comparatively lower kow. Since the HCH isomers occur in dissolved as well as in adsorbed phase because of their low kow in melting snow, we observe an enrichment of the dissolved phase within the first fractions of melt water and of the adsorbed phase within the final fractions of melt water.