Carbonaceous aerosol measurements at two Serbian urban-background sites

Abstract

Carbonaceous aerosol, including elemental carbon (EC) and organic carbon (OC), constitutes a major fraction of atmospheric aerosol mass, impairing air quality. Its role in direct and the indirect climate effects, as well as adverse health effects, highlights the need for regular monitoring. EC results from incomplete combustion of fossil fuels and biomass, with sources including vehicle exhaust, residential wood combustion, and wildfires. Particulate OC is co-emitted with EC during combustion but also forms through gas-to-particle conversion, forming secondary organic aerosol. Additionally, primary biological aerosol particles contribute to the atmospheric OC burden [1]. While OC and EC are regularly measured in major monitoring networks, such as the European Monitoring and Evaluation Programme, large regions, including Serbia, still lack such measurements. The recently adopted EU Directive 2024/2881, "On Ambient Air Quality and Cleaner Air" [2], mandates the analysis of PM with respect to OC and EC. As a part of the WeBaSOOP-project (Research Reinforcing in the Western BalkanS in Off-line and Online Monitoring and Source identification of Atmospheric Particles), we have performed such analysis. Over a nine-month period, OC and EC measurements in PM10 were conducted at two urban background sites in Serbia: the recreational area of Ada Ciganlija in Belgrade and the industrially influenced city park in Bor. Aerosol filter samples were collected every second day using as low-volume sampler operating for 24 hours. OC and EC were analysed using thermal-optical analysis following the EUSAAR_2 protocol. Median OC and EC concentrations showed a clear seasonal pattern at both sites, with higher levels during the heating season. Increased EC levels suggest increased emissions from combustion sources. OC and EC levels were consistently higher in Belgrade than in Bor, though the difference was less pronounced for the heating season. This disparity likely reflects Belgrade’s larger population and greater number of emission sources typical of a major city. Ongoing analysis of organic tracers, including the biomass burning tracer levoglucosan, will provide further insight into the sources of the carbonaceous aerosol in both Belgrade and in Bor.