Ministerial Decree no. 261 of 01/10/2002 "Regulation containing thetechnical directives for the preliminary assessment of ambient air quality, thecriteria for the preparation of the plan and programs referred to in articles 8and 9 of Legislative Decree 4 August 1999 , n. 351" identifies thedispersion models as a useful tool for:
- "To obtain concentration camps also in portions of territory where there are no measurement points, or to extend the spatial representativeness of the measure itself;
- To obtain information on the relationships between emissions and inputs (source and receptor matrixes), thus discriminating between the contributions of the various sources;
- Evaluate the impact of unmeasured pollutants from the monitoring network;
- Study hypothetical scenarios of alternative emissions compared to the current or past framework ".
Odor dispersion modeling allows to quantify the osmogenic impact of the plant on the surrounding territory and is based on olfactometric data, meteorological data and territory orography. It provides a precise indication of the olfactory impact caused by a plant in the surrounding areas.The main steps in the construction of a dispersion model are:
- Identification of the emission sources;
- Acquisition of meteorological data (for example from ARPA control units), orography and land use;
- Simulation of the odors and / or pollutants fallout;
The use of dispersion modeling to evaluate the olfactory impact at sensitive receptors is recommended by the Guidelines of the Lombardy Region "Guidelines for the characterization and authorization of gaseous emissions into the atmosphere of odoriferous impact activities" issued with Deliberazione Giunta Regional of February 15th 2012 - n. IX / 3018, which act as a reference at the national level.
The dispersion models are, today, the only tool that allows to make"predictive" assessments on the potential fallout of pollutants andsmells on the territory, before the realization of the plant itself.
Themain applications of dispersion modeling are:
- Forecasting assessments of the impact of atmosphericemissions of odors and pollutants for authorization purposes (AIA, VIA ...);
- Evaluation of the impact of atmospheric emissions starting from the resultsobtained through olfactometric sampling carried out on the emission sourcesalutazioni.
