Analisi di relazioni empiriche per la conversione delle concentrazioni medie annue di NOx in NO2 nell area urbana di Torino

Generally, both data measured in the air quality stations and numerical model simulations refer to NOX concentration. However, the national and international regulations fix limits for NO2 concentration, thus, to make comparisons with the regulation limits, it is necessary to convert NOX concentration into NO2 concentration. The relationships allowing such a conversion are empirical and are determined on the basis of statistical analyses of measured data and, hence, depend upon on orographic and climatic characteristics of the studied sites. In this work we firstly aimed at verifying the agreement between relationships known in the literature with data gathered by the air quality network of Turin Province. Following the regulations we considered the annual concentration mean and the 99.8 percentile. We found a significant disagreement with measured data. Consequently, our work proceeded to estimate new values of the same empirical conversion relationships, through statistical regressions on the available data, obtaining a noticeable improvement.