Inter-comparison of ammonia fluxes obtained using the Relaxed Eddy Accumulation technique
Hensen, A.; Nemitz, E.; Flynn, M.J.; Blatter, A.; Jones, S.K.; Sørensen, L.L.; Hensen, B.; Pryor, S.C.; Jensen, B.; Otjes, R.P.; Cobussen, J.; Loubet, B.; Erisman, J.W.; Gallagher, M.W.; Neftel, A.; Sutton, M.A.. 2009 Inter-comparison of ammonia fluxes obtained using the Relaxed Eddy Accumulation technique. Biogeosciences, 6. 2575-2588. 10.5194/bg-6-2575-2009Full text not available from this repository.
The exchange of Ammonia (NH3) between grassland and the atmosphere was determined using Relaxed Eddy Accumulation (REA) measurements. The use of REA is of special interest for NH3, since the determination of fluxes at one height permits multiple systems to be deployed to quantify vertical flux divergence (either due to effects of chemical production or advection). During the Braunschweig integrated experiment four different continuous-sampling REA systems were operated during a period of about 10 days and were compared against a reference provided by independent application of the Aerodynamic Gradient Method (AGM). The experiment covered episodes before and after both cutting and fertilizing and provided a wide range of fluxes −60–3600 ng NH3 m−2 s−1 for testing the REA systems. The REA systems showed moderate to good correlation with the AGM estimates, with r2 values for the linear regressions between 0.3 and 0.82. For the period immediately after fertilization, the REA systems showed average fluxes 20% to 70% lower than the reference. At periods with low fluxes REA and AGM can agree within a few %. Overall, the results show that the continuous REA technique can now be used to measure NH3 surface exchange fluxes. While REA requires greater analytical precision in NH3 measurement than the AGM, a key advantage of REA is that reference sampling periods can be introduced to remove bias between sampling inlets. However, while the data here indicate differences consistent with advection effects, significant improvements in sampling precision are essential to allow robust determination of flux divergence in future studies. Wet chemical techniques will be developed further since they use the adsorptive and reactive properties of NH3 that impedes development of cheaper optical systems. [abstract from: http://www.biogeosciences.net/6/2575/2009/bg-6-2575-2009.html]
|Programmes:||CEH Topics & Objectives 2009 onwards > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...|
|Additional Information:||Full text available via the Official URL link. Open access journal. Paper published in Biogeosciences 6 (Special Issue): Processes controlling the exchange of ammonia between grassland and the atmosphere (GRAMINAE), edited by K.Pilegaard, J.K. Schjoerring and M.A. Sutton.|
|NORA Subject Terms:||Atmospheric Sciences|
|Date made live:||17 May 2010 11:05|
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