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United States Department of Agriculture

Agricultural Research Service

Title: Dissolved Gas Analysis for Assessing Nitrate Fate N in a Riparian Wetland

Authors
item Mookherji, Swati
item McCarty, Gregory

Submitted to: Riparian Ecology and Management in Multiland Use Watersheds Meetings
Publication Type: Abstract Only
Publication Acceptance Date: December 21, 2000
Publication Date: N/A

Technical Abstract: The ability of riparian wetland ecosystems to remove groundwater nitrate is well established but the inability to directly measure the fate of nitrate in groundwater makes it difficult to routinely monitor denitrification within these ecosystems. The wetland system under study is associated with a first-order stream next to an agricultural field where groundwater nitrate flows laterally towards a forested riparian buffer. Transects of nested monitoring piezometers were installed in upwelling regions of the wetland with influx of groundwater nitrate. The use of dissolved gas analysis was evaluated for direct assessment of nitrate reduction in groundwater. Detection of denitrification in groundwater involves measurement of dissolved N gases (N20 and N2) with determination of the excess N2 formed by nitrate reduction. This method uses argon (Ar) content in water as a natural conservative tracer for assessing background content of N2 caused by a previous air-water equilibrium. The technique fo groundwater sampling and preservation for later gas analysis in the laboratory is relatively simple and provides a routine, rapid means for surveying groundwater systems for denitrification. This method is sufficiently sensitive to permit detection of small attenuation changes in nitrate reduction to N gas in natural groundwater.

Last Modified: 9/20/2014
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