Persistent nitrate in alpine waters with changing atmospheric deposition and warming trends

Environmental Science and Technology
By: , and 



Nitrate concentrations in high-elevation lakes of the Colorado Front Range remain elevated despite declining trends in atmospherically deposited nitrate since 2000. The current source of this elevated nitrate in surface waters remains elusive, given shifts in additional nitrogen sources via glacial inputs and atmospheric ammonium deposition. We present the complete isotopic composition of nitrate (δ15N, δ18O, and Δ17O) from a suite of nitrate-bearing source waters collected during the summers of 2017–2018 from two alpine ecosystems to constrain the provenance of elevated nitrate in surface waters during the summer open-water season. The results indicate a consistent contribution of uncycled atmospheric nitrate throughout the summer (13–23%) to alpine lakes, despite seasonal changes in source water inputs. The balance of nitrate (as high as 87% in late summer) is likely from nitrate production within the catchment via nitrification of reduced nitrogen sources (e.g., thawed soil organic matter and ammonium deposition) and released with rock glacier meltwater. The role of microbially produced nitrate has become increasingly important over time based on historical surface water samples from the mid-90s to present, a trend coincident with increasing ammonium deposition to alpine systems.

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Publication type Article
Publication Subtype Journal Article
Title Persistent nitrate in alpine waters with changing atmospheric deposition and warming trends
Series title Environmental Science and Technology
DOI 10.1021/acs.est.1c02515
Volume 55
Issue 21
Year Published 2021
Language English
Publisher American Chemical Society Publications
Contributing office(s) Fort Collins Science Center
Description 11 p.
First page 14946
Last page 14956
Country United States
State Colorado
Other Geospatial Front Range
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