Measurements of ammonia emissions from spreading of manure using gradient FTIR techniques

Emissions of biogenic trace gases from soils and plants often show strong s patial and temporal variation. Thus, there is a need for the development of area-integrating measurement techniques with good time resolution. The pre sent paper describes area-integrated measurements of ammonia emissions afte r spreading of pig slurry on a wheat field, based on flux-gradient measurem ents using Fourier transform infrared (FTIR) spectroscopy. Two methods are described; the aerodynamic method where the flux is derived from measured m icrometeorological parameters, and a tracer method where the flux is derive d from simultaneous measurements of a tracer gas released over the area und er study. Although not ideal in the actual measurement situation, this latt er method has a potential for use on more local sources with less restricti ons on micrometeorological conditions, and is thus included for validation. A code for modelling of the "footprint" of gradient measurements is also d escribed, and is used to compare the results from the above-mentioned metho ds. (C) 2000 Elsevier Science Ltd. All rights reserved.