Spatial variation, temporal evolution, and source direction apportionment of PM, PM, and PM: 3-year assessment in Turin (Po Valley).

As the population of urban areas is increasing continually, analysis of the particulate concentration dynamics in these areas is crucial. Therefore, this study investigated the temporal and spatial variabilities of PM, PM, and PM over the urban area of Turin in the Po Valley, Italy, based on high-resolution data from a monitoring campaign conducted between 2018 and 2021 (including COVID-19 lockdown period). The study also performed a source direction analysis of the urban observation using the conditional bivariate probability function (CBPF). The results showed substantial differences in PM concentration at background (28-30 µg/m), and traffic stations (36 µg/m). PM concentration was highest at traffic stations (24 µg/m). During the day, the highest values occurred at 9:00-11:00 AM, and the lowest concentrations occurred at 4:00-6:00 PM. The concentration peak position changed in a daily bimodal trend with the season. According to the CBPF, the relevant external particulate contributions to the Turin area are from the direction of the Po Valley (N-NE) and the typical direction of Saharan dust transport (S-SW). The present study contributes to scientific understanding by providing information on one of the main European pollutant hot spots and discussing the trends of emerging pollutants, like PM.