Il particolato atmosferico nell'area urbana di Ancona: distribuzione dimensionale e valutazione delle sorgenti di metalli pesanti e nitro-IPA

Air pollution, and particulate matter (PM) in particular, is one of the main environmental challenges of modern urban areas. This study focuses on the analysis of the chemical composition and size distribution of PM in the urban area of Ancona, a city located along the central Adriatic coast, strongly influenced by maritime traffic and industrial activities. In recent decades, scientific research has highlighted the significant impacts of PM on public health and the environment, making it necessary to have an in-depth understanding of its sources and characteristics. Atmospheric particulate matter is a complex mixture of solid and liquid particles suspended in the air, ranging in size from a few nanometers to tens of micrometers. PM sources can be both natural and anthropogenic. Particles can be emitted directly (primary PM) or formed through gas-particle conversion reactions (secondary PM). This research aims to analyze in detail the chemical composition of PM, with particular attention to heavy metals and nitroderivatives of polycyclic aromatic hydrocarbons (nitro-PAHs), in an urban context characterized by significant polluting pressures. During the research, two atmospheric particulate matter sampling campaigns were conducted: the first between July 2021 and March 2022 and the second from June to September 2022. The campaigns involved the use of cascade impactors to collect PM10 fractions, allowing for a detailed analysis of particle size and chemical composition. The collected samples were analyzed in the laboratory using differential filter weighing and advanced analytical techniques to determine the concentration of heavy metals and nitro-PAHs. The results obtained highlighted the strong impact of port activities and maritime traffic on the air quality in Ancona. During the weekends when the port was operational, significant increases in PM10 concentrations were recorded, indicating a clear correlation between port activities and atmospheric pollution. Chemical analyses revealed high concentrations of heavy metals such as aluminum, iron, manganese, arsenic, cadmium, chromium, copper, mercury, nickel, lead and vanadium. These metals are known for their toxic effects on human health, aggravating respiratory and cardiovascular conditions. Furthermore, nitro-PAHs, organic compounds derived from the oxidation of polycyclic aromatic hydrocarbons, were analyzed for their potential toxicity. The results showed that the concentrations of nitro-PAHs were below the limits of quantification, suggesting that further studies are needed to better understand their presence and their impact on public health. The size distribution of PM10 showed a bimodal structure, with one accumulation mode in the 0.1-1.0 µm range and one coarse mode in the 1.0-10.0 µm range. This distribution highlights the need to specifically monitor the different size classes of particles to identify and quantify anthropogenic emission sources. The data obtained suggests that PM10 is equally distributed between the two modes, with a significant impact on air quality and public health. The research also examined the seasonal variations in PM10 concentrations, dividing the sampling period into two macro-ranges: the cruise period and the winter lay-up period (WLP) of cruise ships. The results showed an unusual seasonal trend, with higher PM10 concentrations in the summer season than in the fall, contrary to what has been observed in other studies. This phenomenon suggests that pollution sources could vary significantly based on the season and port activity. Principal component analysis (PCA) was applied to discern seasonal contributions and the various sources of pollution. The results showed that the major constituent elements, such as Al and Fe, are mainly associated with natural and industrial sources, while metals such as Cu, Cd, As, Pb and Ni show strong correlations with anthropic activities, particularly those related to vehicular traffic and port operations. In conclusion, this study offers an important understanding of the chemical composition, size distribution and sources of atmospheric particulate matter in the urban area of Ancona. The results obtained have significant implications for air quality planning and management, suggesting the urgency of implementing mitigation strategies to address the challenges related to air pollution. Continuous and in-depth monitoring of air pollutants is essential to ensure a healthier and more sustainable environment for future generations. The research emphasizes the importance of targeted intervention strategies, based on scientific data, to improve air quality and protect public health in highly polluted urban contexts such as Ancona.