Road Salt Influence on Pollutant Releases from Melting Urban Snow

A snow-melting experiment was performed to study the effects of road salt on the melting of urban snow from a snow wind-row (pile) along a road in central Luleå, Sweden. Two snow piles were formed in the laboratory, with and without road salt added, and melted under similar conditions. All meltwater was collected and analyzed. The purpose of the experiment was to study the influence of the use of de-icing salt on meltwater quality and the release of pollutants from urban snow. The study indicated that the use of road salt may increase the dissolved metal phase in the urban snow meltwater. Also, the salt seems to have the largest effect at the beginning of the melting period when chloride is leaving the snow pile. Of total chloride, 90% was transported with the first 20 % of the meltwater. Concentrations of the particulate-bound metals showed a fairly constant rate of release at the start of melt, but increased rapidly towards the end of the melting period, and this was more pronounced in the case of snow containing high chloride concentrations. Overall, a larger transport of solids was found for the pile with salt due to faster melting. Significantly larger masses of suspended solids and two heavy metals (Cu and Zn) were released with the meltwater from the pile with salt in comparison with the no-salt pile. The rest of the suspended solids and heavy metals stayed in the solid residue remaining at the end of the experiment