DEVELOPMENT OF A SIMULATION TOOL TO EVALUATE THE APPLICABILITY OF THE GRADIENT METHOD FOR THE ESTIMATION OF ODOUR EMISSION FLUXES

Micrometeorological methods are commonly used in agro-meteorology for the estimation of biogenic emissions. Despite being often mentioned, their practical application for indirect estimation of odour emission rates is extremely rare. Among the existing methods, this work focused on the Gradient Method and the main objective was to identify the technical characteristics required for analysers to be used for the estimation of odour fluxes. This valuation was carried out through the implementation of a flexible simulation tool which, by using reference odour fluxes and real meteorological data measured during the year 2015 by an ultrasonic anemometer (Tor Vergata, Rome), made it possible to recreate the functioning of a measuring device, and thus to assess a priori the possibility of applying these methods. For this purpose, the absolute concentration and concentration difference at the measurement point were determined in order to assess the limits of detection and resolution required by the odour analyser. The results showed that for an odour flux of 1 ou E /m 2 /s, if 50 ou E /m 3 is taken as the lower resolution limit for odour concentration measurements, the percent data that could hypothetically result above this limit would be 33.3% if considering two measurement heights of 0.5 and 3.5 , and 44.3% if considering two measurement heights of 0.5 . Similar considerations can be made based on analysis of the absolute concentration measured at the two sampling heights. Moreover, the influence of atmospheric stability on the data above the background odour has been investigated: the measurement of the concentration gradient as well as of the absolute concentration, regardless of the chosen measurement heights, is only feasible under the conditions described by categories D and F. In conclusion, the gradient method represents an attractive and potentially applicable alternative for estimating odour emissions, since the developed simulation tool has demonstrated to be suitable to evaluate the conditions of applicability of the method as a function of specific emission and meteorological conditions. However, the effective direct applicability to the odour concentration requires further study and experimental campaigns.