Iasonas Stavroulas

Sarajevo is the most PM2.5-polluted European capital (IQAir Report, 2024); however, fine aerosol measurements studies in the city are scarce. This study presents the results of an 8-month campaign in Sarajevo site focusing on organic aerosol (OA) and equivalent black carbon (eBC) and their respective sources. The mean PM1 campaign concentration in Sarajevo is 34.2 μg·m-3 with significantly higher contributions in winter stagnation episodes during which daily concentrations can exceed 100 μg·m-3. Furthermore, the number of daily PM1 concentrations during this 8-month campaign exceeding the EU legislation PM2.5 limit value are more than 4 times the stated maximum number of days per year. The eBC sources consist of liquid fuel (eBClf, 62%), and solid fuel (eBCsf, 38%) combustion, the latter proportion being higher than in other European sites. OA source apportionment results revealed 4 factors: hydrocarbon-like OA (HOA, 15%), two solid fuel combustion OA (SFOA1, 31%; SFOA2, 9%), and oxygenated OA (OOA, 44%). HOA and eBClf are related to traffic emissions; SFOA1, SFOA2, and eBCsf are associated with residential heating, although SFOA2 potentially reflects additional regional combustion sources; and OOA shows regional, secondary aerosol characteristics with biomass burning emissions influence. Accordingly, Sarajevo's burden from air pollution could lead to all-cause mortality on the order of 10% during its heavy-polluted episodes. Overall, the submicron aerosol in Sarajevo constitutes a hotspot of fine pollution in comparison to other European sites both in its absolute concentrations and its relative proportion of biomass burning and SO42-, making this hotspot more comparable to those observed in other global hotspots than to typical European urban backgrounds.

Greater Cairo, the most populous megacity in the Middle East North Africa (MENA) region, faces severe aerosol pollution, posing a significant threat to public health. Despite its impact, the main sources of pollution remain under-characterized due to sparse atmospheric observations. To address this gap, we conducted a continuous two-month field study at an urban background site, documenting the first chemical and physical properties of submicron aerosols (PM1). We found that crustal material from both desert dust and traffic dust resuspension accounted for as much as 24% of the total PM1 mass, increasing to 66% during desert dust events—a level unusually high for urban settings. Simultaneously, our data indicated reductions in black carbon and ammonium sulfate levels, suggesting successful emission reductions through local and regional mitigation efforts. The diurnal patterns of carbonaceous aerosols were linked to peak emissions from local traffic during rush hours and from open biomass burning at night. Contrarily, our analysis identified unexpectedly high levels of semi-volatile ammonium chloride (NH4Cl) from local open biomass and waste burning, emerging as the predominant PM1 chemical species in Cairo. Its formation at night significantly influenced morning aerosol water uptake, thereby playing a crucial role in the formation of persistent urban haze. These findings not only confirm the ongoing presence of a significant dust reservoir over Cairo but also reveal a new source of highly hygroscopic semi-volatile inorganic salts, leading to a unique type of urban haze. This haze, characterized by major contributions from both submicron and supermicron particle modes, highlights the complex implications of heterogeneous chemical transformations of air pollutants in urban settings, emphasizing the need for interdisciplinary research to understand and mitigate these impacts in the Mediterranean and similar regions. Full details are available in our publication in Christodoulou et al., 2024.Christodoulou, A., Bezantakos, S., Bourtsoukidis, E., Stavroulas, I., Pikridas, M., Oikonomou, K., Iakovides, M., Hassan, S. K., Boraiy, M., El-Nazer, M., Wheida, A., Abdelwahab, M., Sarda-Estève, R., Rigler, M., Biskos, G., Afif, C., Borbon, A., Vrekoussis, M., Mihalopoulos, N., Sauvage, S., and Sciare, J.: Submicron aerosol pollution in Greater Cairo (Egypt): A new type of urban haze?, Environ. Int., 186, https://doi.org/10.1016/j.envint.2024.108610, 2024.

Fine particulate matter (PM) poses a major threat to public health, with organic aerosol (OA) being a key component. Major OA sources, hydrocarbon-like OA (HOA), biomass burning OA (BBOA), and oxygenated OA (OOA), have distinct health and environmental impacts. However, OA source apportionment via positive matrix factorization (PMF) applied to aerosol mass spectrometry (AMS) or aerosol chemical speciation monitoring (ACSM) data is costly and limited to a few supersites, leaving over 80% of OA data uncategorized in global monitoring networks. To address this gap, we trained machine learning models to predict HOA, BBOA, and OOA using limited OA source apportionment data and widely available organic carbon (OC) measurements across Europe (2010–2019). Our best performing model expanded the OA source data set 4-fold, yielding 85 000 daily apportionment values across 180 sites. Results show that HOA and BBOA peak in winter, particularly in urban areas, while OOA, consistently the dominant fraction, is more regionally distributed with less seasonal variability. This study provides a significantly expanded OA source data set, enabling better identification of pollution hotspots and supporting high-resolution exposure assessments.

Cooking, one of key human activities, has been known to contribute significantly to ambient aerosol in both the indoor and outdoor settings. In certain urban environments, cooking Organic Aerosol (OA) have been documented to drive outstanding smog events. On the other hand, more research is necessary on induced health effects by such aerosol. A controlled, cooking and grilling experiment was performed in June 2024 in an effort to physically and chemically characterize cooking aerosol and derive estimations on their oxidative potential. Along the way, the response of the Aerosol Chemical Speciation Monitor (ACSM) to direct cooking emissions was assessed, while reference single source mass spectra were acquired, to be used as an important aid for constraining algorithms performing source apportionment of ambient aerosol. Various cooking conditions (gas vs charcoal grill, frying pan) were tested on different types of food (vegetables, steaks, burgers, chicken, fish, fries, etc). The experimental setup included an ACSM, a 7-wavelength filter-based absorption photometer (AE-33 aethalometer), a Scanning Mobility Particle Sizer (SMPS) providing number size distributions and filter sampling of PM2.5 aerosol to perform off line detailed composition analysis and oxidative potential estimates. Acquired OA mass spectra presented similarities, being dominated by prominent signals at m/z = 41, 43, 55 and 57, linked to the fragmentation of alkyls and specifically the CnH2n+1 and CnH2n-1 ion series. All cooking spectra acquired, share the common feature of an m/z = 55 over m/z = 57 contribution ratio (i.e. f55/f57) well above unity. The contribution of significant signal at m/z = 60, a typical tracer of the fragmentation of levoglucosan, related to the pyrolysis of cellulose was evident in the mass spectra of charcoal grilled food. Interestingly non negligible, nevertheless low contributions at m/z = 60, were also found for food cooked on a gas burner grill. Grilling vegetables yields pronounced contributions at higher m/z values (e.g. for m/z =67, 69, and 71). The largest contribution at m/z = 44 in the mass spectrum, was observed when sampling aerosol from burning the residual fat from a heated pan.Acknowledgement: This work is supported by the European Union's Horizon Europe research and innovation programme under the Marie Skłodowska-Curie Postdoctoral Fellowship Programme, SMASH co-funded under the grant agreement No. 101081355. The SMASH project is co-funded by the Republic of Slovenia and the European Union from the European Regional Development Fund.

Although production of legacy industrial-grade Persistent Organic Pollutants (POPs) has been prohibited since the early 00’s, residues are still present in all environmental compartments, whereas illicit usage is still documented at a global scale. Unauthorized disposal activities of Aroclor technical mixtures and illegal incineration of obsolete electronic equipment are also primary sources of significant environmental concern.Island of Cyprus, situated at the easternmost side of the Mediterranean Basin, is surrounded by large urban and industrial areas and comprises a unique location for exploring air quality over the broader Eastern Mediterranean and Middle East (EMME) region. The present work extends previous reports on the occurrence and fate of a wide spectrum of highly toxic compounds in the atmosphere over Cyprus and explores comprehensively the atmospheric distribution of polychlorinated naphthalenes (PCNs) and polybrominated diphenyl ethers (PBDEs), both listed under the Stockholm Convention text.Total (gaseous and particulate phase) concentrations of the scarcely monitored in EMME region PCNs were measured similar to urban locations. Contrarily, the corresponding levels of PBDEs were comparable to background areas, exhibiting a relative enrichment in congeners with intermediate degree of bromination. Regressions of logarithms of partial pressure against ambient temperature for PCNs revealed that secondary recycling from contaminated terrestrial surfaces regulates their atmospheric variability. Enthalpies of surface-air exchange (ΔHsa) for PCNs were significantly correlated to vaporization enthalpies (ΔHv) determined by chromatography, corroborating the presence of short-range revolatilization processes. Homologue concentration ratios of PCNs suggested inputs from thermal processes, whereas potential evaporation from Aroclor-contaminated surfaces cannot be excluded. An inverse pattern for PBDEs was observed. The corresponding regression slopes were shallow, implying long-range atmospheric transport, whereas ΔHsa were insignificantly correlated with ΔHv, suggesting that, unlike PCNs, volatilization sources of PBDEs are of minor importance.We also evaluated gas/particle partitioning by utilizing a comprehensive range of traditional and novel partitioning models. Additionally, we constructed, separately for PCNs and PBDEs, temperature-dependent quantitative structure-property relationship (QSPR) models based on quantum-mechanical descriptors. Equilibrium-state models predicted well the gas/particle partitioning quotients (Kp) of PCNs, whereas steady-state models predicted better the partitioning behavior of PBDEs. Both empirical QSPR models exhibited equal performance in predicting Kp and can be used as reference for studies under similar temperature ranges around the globe. Acknowledgements: The present work received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 856612 (EMME-CARE) and the Cyprus Government.