Assessing the severe urban pollution crisis in Sarajevo, Bosnia and Herzegovina: mobile measurements and source characterization

Particulate air pollution is the leading environmental risk factor, contributing substantially to global morbidity and mortality. In the Western Balkans, air quality during winter months is among the poorest observed in Europe. Nevertheless, detailed chemical characterization of air pollution in the region remains limited, although such information is essential for identifying emission sources and supporting effective mitigation strategies. Therefore, a mobile measurement campaign was conducted in Sarajevo (Bosnia and Herzegovina) in January 2023 as part of the SArajevo AEROsol Experiment (SAAERO). The spatial distribution and chemical composition of particle- and gas-phase pollutants were investigated using multiple high-resolution instruments. Organic aerosol (OA), as a key component, accounted for 59% of the total submicron particulate matter (PM₁). Source apportionment of the OA using Positive Matrix Factorization (PMF) resolved five distinct sources: two solid fuel combustion sources (SFC1 and SFC2), traffic (HOA), cooking (COA), and oxygenated OA (OOA). While daytime variation across the city was limited, an east-west pollution gradient emerged during evening hours, largely driven by SFC. SFC contributions to OA ranged from 45 to 54 % in predominantly residential areas outside the city center and amounted to 35 % in the center. In contrast, COA was highest in the center (14%), spatially aligned with restaurant locations. These findings show that pollution sources contribute non-uniformly in different parts of Sarajevo especially during evening hours. By combining spatially resolved measurements with source apportionment, this study provides valuable insights into pollution sources and their chemical composition in Sarajevo, a highly polluted but still largely understudied area in Europe.