Critical Analysis of the Results of a Network System for Nitrogen Dioxide Monitoring

Data relative to the nitrogen dioxide concentrations of seventeen fixed monitoring stations in three provinces in Po Valley in Northern Italy are analysed. NO2 is considered to be one of the most harmful air pollutants, mainly due to vehicle traffic in urban environments. According to the EU directives, different categories of monitoring sites are identified as being representative of different situations. The main objective of this study was to check the agreement of the classification of monitoring sites with the chemical measurements of the actual atmospheric NO2 pollution. The analysis considered the whole year of 2022 and even included the consideration of single months; the aim was to identify seasonal effects. The data were treated using different chemometric techniques, and the results obtained from significance tests were consistent with those of cluster analyses. In particular, both approaches to the treatment of the chemical data indicate that the level of NO2 pollution may be significantly different from one station to another, even within the same category, and may produce results that are more similar to those of different categories, both inside the same province and in different provinces. Beyond local interest, this work also acts as a case study, attempting to offer a path for a common approach to effective reproducible monitoring procedures toward shared environmental sustainability.