Mass balance techniques for trace gas emissions measurements from soil and plant canopies

Micrometeorological methods for measuring fluxes of gases between the land surface and the atmosphere are non-invasive. In fact, these methods do not interfere with natural environmental processes of gas exchange. Purpose of this study is to adapt the Micrometeorological Mass Difference (MMD) technique to monitor CO2, water vapour and other trace gas fluxes at the small plot level. The technique can be used to measure methane and carbon dioxide emission from landfills, methane production by grazing animals, trace gas emission from waste products and from agricultural soils, photosynthesis and transpiration of plant canopies. A description is given of the apparatus developed at CNR-ISAFOM and data are reported concerning the performance of the flux-measuring device by releasing CO2 at a known rate. This work is the first study aimed at developing non-invasive methodologies to measure NH3, CH4, CO2, and N2O emissions/absorptions in a Mediterranean environment. An evolution of the method, which implies the use of tracers and makes for a much simple field apparatus, was also tested by running CFD numerical simulations and reconstructing scalar concentration in the fields.