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Stable sulfur isotope ratios and major ions in bulk snowpack samples were monitored at a network of 52 high-elevation sites along and near the Continental Divide from 1993 to 1999. This information was collected to better define atmospheric deposition to remote areas of the Rocky Mountains and to help identify the major source regions of sulfate in winter deposition. Average annual δ34S values at individual sites ranged from +4.0 to +8.2‰ and standard deviations ranged from 0.4 to 1.6‰. The chemical composition of all samples was extremely dilute and slightly acidic; average sulfate concentrations ranged from 2.4 to 12.2 μeq l−1 and pH ranged from 4.82 to 5.70. The range of δ34S values measured in...
Volume-weighted mean concentrations of nitrate (NO3?), ammonium (NH4+), and sulfate (SO42?) in precipitation were compared at high-elevation sites in Colorado from 1992 to 1997 to evaluate emission source areas to the east and west of the Rocky Mountains. Precipitation chemistry was measured by two sampling methods, the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) and snowpack surveys at maximum accumulation. Concentrations of NO3? and SO42? in winter precipitation were greater on the western slope of the Rockies, and concentrations of NO3? and NH4+ in summer precipitation were greater on the eastern slope. Summer concentrations in general were almost twice as high as winter concentrations....