Analysis of air quality in the urban area of Turin: Focus on nitrogen oxides and particulate matter

This thesis uses information collected from five monitoring stations between 2000 and 2022 to present a comprehensive database analysis of the air quality in the urban area of Turin, with a focus on nitrogen oxides and particulate matter. The goal is to demonstrates a methodology for approaching pollutant concentration databases, and assess the impact of regulatory measures on air quality, determining whether introduced environmental policies have influenced the concentrations of nitrogen oxides (NO, NO$_2$, NO$_x$) and particulate matter (PM$_{10}$ and PM$_{2.5}$). The study uses publicly available datasets, that provide detailed daily and hourly measurements of pollutant concentrations from the Sistema Regionale di Rilevamento di ARPA Piemonte (database accessible at \href{https://aria.ambiente.piemonte.it/\#/qualita-aria/dati}{https://aria.ambiente.piemonte.it/\#/qualita-aria/dati}). The work on the database begins with characterizing the different measurement methods employed at each station, assessing their reliability and comparability. A geographical map illustrates the spatial distribution of the stations, complemented by an evaluation of data coverage that highlights measurement variability over time. This analysis gives an overview on when each station began operating and highlights key periods of reliable data collection, providing insights into the functionality and data quality of each station. The raw data were reorganized and cleaned to ensure accuracy, underling inconsistencies and filling data gaps where possible. This process helped to highlight significant trends, gaps, and possible errors in the measurements over the years. In the main part of the thesis, Long-term trends in pollutant levels are analyzed using both simple linear trend analysis and advanced techniques such as STL (Seasonal and Trend decomposition using Loess), which helps firtly to provide a general view of the pollution levels, and secondly to identify trends, seasonal patterns, and irregular changes in the data that are not immediately visible. Additionally, a preliminary exploration of the potential use of the cleaned dataset in the Urban Atmospheric Pollutant Dispersion Model SIRANE, is provided. This stresses its possible future application in studies focused on the area of Turin. The results of this thesis present a comprehensive view of air quality database, providing insight on data reliability and measurement trends and variability, across Turin over the first two decades of the 21st century. The analysis evidence an improvement in air quality condition, with decreasing trends in nitrogen oxides and particulate matter concentrations. This reduction is mainly attributed to the implementation of stringent environmental policies, demonstrating the effectiveness of the regulations introduced by the European Parliament and concretely adapted by the city of Turin. This work not only provides a clear perspective on the historical and current state of urban air quality in Turin but also provides a valuable reference for future air quality comparisons and air pollution management in the metropolitan area.