Eddy Covariance Flux Measurements of NH3 and NOy with a Dual-Channel Thermal Converter

Surface-atmosphere exchange of reactive nitrogen (N
r
) plays a major role in the nutrient availability or loss of (semi-) natural and agricultural ecosystems. We present a fast response dual-channel converter for the eddy covariance flux measurement of oxidized and reduced N
r
compounds. The system was tested over a managed pasture system and during release experiments with an artificial emission source. The measured concentrations showed good agreement with the sum of independent specific measurements of NO, NO2 and NH3. Generally, emissions of reduced N
r
(attributed to NH3) were much larger than deposition of NO
y
for the pasture field. A slurry spreading by trailing hose in late winter showed moderate but significant NH3 emissions lasting for about eight days.