Research article
A 50-year record of NOx and SO2 sources in precipitation in the Northern Rocky Mountains, USA
1 U.S. Geological Survey, 2329 W. Orton Circle, Salt Lake City, UT 84119, USA
2 U.S. Geological Survey, 3215 Marine Street, Suite E-127, Boulder, CO 80303, USA
3 U.S. Geological Survey, Denver Federal Center, MS 963, Denver, CO 80225, USA
Geochemical Transactions 2011, 12:4 doi:10.1186/1467-4866-12-4
Published: 7 March 2011Abstract
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.
