Studies of pollutants and modeling
A comprehensive study concerning air quality in a specified area is mainly composed by three different synergic stages:
1. In situ monitoring;
2. Analytical and modeling study;
3. Possible Recovery Plan.
Environmental monitoring systems represent the basic instrument for exploratory analysis of the actual state of the territory and for the control of pollution levels.
In this field, however, it is also essential to carry out analytical studies supported by the use of specific mathematical models, in order to fully evaluate the overall pollutant concentrations in the examined area and their diffusion and dilution caused by local meteorological phenomena.
At the end of the study, if needed, it is possible to determine Actions aimed at air quality Restoration to reduce pollutant concentrations below threshold limits.
These procedures define the principal phases of appropriate Air Pollution Recovery Plans.
System modeling plays a key role in order to obtain an adequate level of knowledge of pollution of territory and a good evaluation of its diffusion in neighbouring areas, both at micro and macro-scale level. It also provides information regarding the direct relation between emissions and concentrations, taking into account both the effects of dispersion and transport processes and the effects related to the phenomena of chemical transformation and removal.
In particular, dispersion models are a necessary and useful tool for:
• obtaining concentration maps, even in areas where there are no measurement points, or extending the spatial reliability of measurements;
• getting information regarding the relation between air emissions and concentrations, taking into account the contributions of the different sources;
• assessing the impact of pollutants not completely evaluated by the monitoring system;
• generating ground concentration “maps” able to cover the entire monitored territory;
• predicting critical events;
• studying alternative emission scenarios showing important differences from classical reference models.
Simulation results are obviously characterized by a certain degree of uncertainty due to model composition (caused by the impossibility to give a perfect description of physical phenomena) and input data variability, in particular concerning emissions and meteorological parameters. Finally, a correct implementation of the model requires a strict comparison with on-site measured data thus allowing its verification and calibration.
The purpose of Air Quality Studies is, therefore, to define in detail the levels of pollution in the specific area for various supposed scenarios and, for each one, to give qualitative and quantitative assessments of predicted pollutant concentrations.
Once defined the numerical values of overall concentrations, thanks to on-site data collection data integrated with the Air Quality Study defined by simulation modeling, it is possible to verify whether threshold values established by Regulations are exceeded or not.
On the basis of the acquired information, it is possible to evaluate the mitigation interventions which may be necessary to reduce the impact on air quality produced by the investigated human activities.
The set of required interventions is determined in a final document, called Air Pollution Recovery and Management Plan, drawn up to implement the restoration of the air quality in the territory.
