Effect of Atmospheric Deposition and Weathering on Trace Element Concentrations in Glacial Meltwater at Grand Teton National Park, Wyoming, U.S.A.

ABSTRACT

Glaciers are reservoirs of atmospherically deposited trace elements that are released during melt. Weathering in glacial environments also contributes solutes to proglacial streams. To investigate the relative importance of atmospheric deposition and weathering on trace element chemistry of glacial streams, we sampled supraglacial and proglacial meltwater at two glacierized catchments in Grand Teton National Park, Wyoming, which is located downwind of agricultural/industrial emissions and dust sources. Concentrations of major ions (Mg²⁺, K⁺, Na⁺, Ca²⁺, SO₄ ²⁻), alkalinity, conductivity, and a subset of trace elements (U, Mo, Sr, Rb, Li, Ba) were low in supraglacial meltwater but increased in proglacial streams because of water-rock interactions. In contrast, concentrations of the trace metals Mn, Co, Zn, Pb, Cd, and Hg had relatively high concentrations in supraglacial meltwater and decreased downstream. These metals are not abundant in the local bedrock and thus are likely sourced from atmospheric deposition. Stable isotopes indicated different water sources in July (snowmelt-dominated) and August (ice melt-dominated), but water chemistry was similar during both months, indicating similar composition of recent snowfall and older ice. These findings have implications for evaluating the relative impacts of atmospheric deposition and weathering in glacier- and snow-dominated catchments.

Acknowledgments

This project was supported by a grant from the University of Wyoming—National Park Service (UW-NPS) Research Station. We thank the research station staff for providing gracious hospitality and logistical support during the fieldwork. We also thank staff at Grand Teton National Park for providing research permits and helping coordinate the fieldwork. Students Joel Johansen, Brian Selck, Dylan Dastrup, Desmond O'Brien, and Timothy Goodsell provided field and laboratory assistance. Financial support was also provided by the College of Physical and Mathematical Sciences and the Department of Geological Sciences at Brigham Young University. We thank two anonymous reviewers whose comments greatly improved the manuscript.