Unprocessed atmospheric nitrate in waters of the Northern Forest Region in the USA and Canada

Environmental Science and Technology
By: , and 

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Abstract

Little is known about the regional extent and variability of nitrate from atmospheric deposition that is transported to streams without biological processing in forests. We measured water chemistry and isotopic tracers (δ18O and δ15N) of nitrate sources across the Northern Forest Region of the U.S. and Canada and reanalyzed data from other studies to determine when, where, and how unprocessed atmospheric nitrate was transported in catchments. These inputs were more widespread and numerous than commonly recognized, but with high spatial and temporal variability. Only 6 of 32 streams had high fractions (>20%) of unprocessed atmospheric nitrate during baseflow. Seventeen had high fractions during stormflow or snowmelt, which corresponded to large fractions in near-surface soil waters or groundwaters, but not deep groundwater. The remaining 10 streams occasionally had some (<20%) unprocessed atmospheric nitrate during stormflow or baseflow. Large, sporadic events may continue to be cryptic due to atmospheric deposition variation among storms and a near complete lack of monitoring for these events. A general lack of observance may bias perceptions of occurrence; sustained monitoring of chronic nitrogen pollution effects on forests with nitrate source apportionments may offer insights needed to advance the science as well as assess regulatory and management schemes.

Publication type Article
Publication Subtype Journal Article
Title Unprocessed atmospheric nitrate in waters of the Northern Forest Region in the USA and Canada
Series title Environmental Science and Technology
DOI 10.1021/acs.est.9b01276
Volume 53
Issue 7
Year Published 2019
Language English
Publisher American Chemical Society
Contributing office(s) New England Water Science Center
Description 14 p.
First page 3620
Last page 3633
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