A 50-year record of NOx and SO2 sources in precipitation in the Northern Rocky Mountains,USA |
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Authors: | David L Naftz Paul F Schuster Craig A Johnson |
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Affiliation: | (1) U.S. Geological Survey, 2329 W. Orton Circle, 84119 Salt Lake City, UT, USA;(2) U.S. Geological Survey, 3215 Marine Street, Suite E-127, 80303 Boulder, CO, USA;(3) Denver Federal Center, U.S. Geological Survey, MS 963, 80225 Denver, CO, USA |
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Abstract: | Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ15N, ) and sulfur (δ34S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ34S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington. The remaining δ34S values were similar to the isotopic composition of coal from southern Wyoming. The δ15N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and all fall within the δ15N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S. emissions data from 1950 to the mid-1970s. |
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