Particulate matter is widely known as a significant air pollutant due to its proven detrimental impact on human health. Furthermore, ultrafine particles (UFPs) are those with diameters smaller than 100 nm, which can cause numerous serious health effects. Thus, identifying the sources of UFPs is essential for formulating effective mitigation strategies. Quantifying the contributions of particle sources can be performed by measuring particle number size distributions (PNSDs) for specific size ranges. This study was conducted in the city of Belgrade, the capital of Serbia, and one of the largest cities in the Balkans peninsula, which, within the European framework, belongs to a region and urban area characterized by high levels of atmospheric particulate matter pollution. In addition, there is a lack of studies addressing UFP levels and their sources in Serbia, including Belgrade. Several criteria pollutants were measured, together with the UFPs and equivalent black carbon (BC) at the urban background site in the city of Belgrade, Serbia, for the period from February to August 2024. The particle sources were analyzed using Positive Matrix Factorization (PMF) of PNSDs along with equivalent BC, PM10, PM2.5, O3, SO2, NO, NO2 and NOx. Seven source types were identified, characterized, and quantified, including two traffic sources (separated into traffic 1 and traffic 2), mixed traffic, an urban diffuse source, nucleation and nucleation growth sources, and a biomass burning source. Traffic-related sources were found to have the most significant contribution at around 40% of total particles emitted, followed by nucleation-related sources (24%) and biomass burning (20%). This is the first study performed in Serbia and Belgrade that addresses source apportionment of PNSD, for particles in the range 10–400 nm.
Ćirović et al. (Mon,) studied this question.