ELUTION AND TRANSPORT OF CONTAMINANTS FROM METAL-RICH ARTIFICIAL SNOW IN COLORADO

A study of the fate and transport of metals in artificial snow was conducted at the Keystone Resort in Colorado to examine potential effects on soils, shallow groundwater, and streams receiving snowmelt drainage. Keystone uses snowmaking water from the Snake River, which receives metal inputs from upstream abandoned mines. Natural and artificial snow (at different depths), snowmelt water (before contacting soils), surface runoff from ski slopes, surface soils, shallow groundwater, and streams were sampled before, during, and after spring snowmelt and analyzed for major cations/anions, metals (Al, Cd, Cu, Fe, Pb, Mn, Zn), DOC, pH, and specific conductance. Snake River concentrations during snowmaking averaged ~350 (Zn) and 230 (Mn) μg/L, and these metals and Cu were elevated in artificial snow. Snowmelt lysimeter samples showed that Zn, Mn, SO₄ and other ions eluted from snow early in the snowmelt cycle; 44-61% of Zn eluted with the first 30% of meltwater at values ~8 times higher than those in the snowpack. Slowest early melt rates produced the highest concentrations, and the ionic pulse from artificial snow was delayed relative to natural snow. Surface runoff concentrations were lower than direct snowmelt values but also peaked early in the snowmelt. Streams with the highest snowmaking coverage (Camp and Mozart drainages) had Zn and Mn values that met stream standards for aquatic life but were substantially higher than those at reference sites, and concentrations peaked during the rising limb of the snowmelt hydrograph. Soils from slopes and wetlands exposed to artificial snow contained higher Zn and Mn concentrations than reference soils, but spring and wetland soil water in snowmaking drainages did not have higher concentrations than reference shallow groundwater samples. The findings demonstrate that metals eluting from artificial snow can be tracked through many environmental compartments, that metals elution peaked when streamflows were relatively low (rising limb of snowmelt hydrograph), similar to trends at many metal mines, and that concentrations in streams have increased but not exceeded aquatic life protection values. Changes in climatic patterns, upstream water diversions, and the amount of snowmaking could potentially change the results, especially under early snowmelt conditions.