Saliou Mbengue

Reliable quantification of organic carbon (OC) is essential for the comparability of long-term aerosol measurements across monitoring networks. A multi-site intercomparison of OC measurements was conducted at three Central European background stations, Melpitz (MEL), Frýdlant (FRY), and Košetice (NAOK), using aerosol mass spectrometry (AMS/ACSM) and thermal-optical transmission (TOT) methods (offline and semi-continuous). Semi-continuous and offline TOT measurements showed high consistency across sites and seasons, suggesting negligible influence of particle size differences on OC comparability. A pronounced seasonal contrast was observed between AMS derived OC (OC_AMS) and TOT based OC (OC_TOT). During summer, good agreement was found with OC_TOT:OC_AMS slopes of 1.27 (MEL), 0.86 (FRY), and 0.83 (NAOK). In winter, AMS systematically underestimated OC, with slopes decreasing to 0.34 (MEL), 0.24 (FRY), and 0.63 (NAOK). The discrepancy increased under combustion dominated conditions and was associated with low organic aerosol to equivalent black carbon (OA:eBC) ratios (<≈5), identifying a regime where OC_AMS and OC_TOT diverge substantially. Source dependent effects were evident, with the largest deviations observed at the coal influenced site (FRY) and during long-range transport events, while improved agreement coincided with higher OA:eBC ratios and enhanced secondary organic aerosol formation in summer. Evaluation of potential uncertainties (including pyrolytic carbon formation in TOT and AMS related limitations such as refractory organics and ionization efficiency) showed that no single factor explains the winter discrepancy, suggesting combined matrix and source effects. The results show that OA:eBC can serve as a practical indicator for OC_AMS-OC_TOT agreement and provide recommendations to improve OC quantification under winter combustion conditions.

Reliable quantification of organic carbon (OC) is essential for the comparability of long-term aerosol measurements across monitoring networks. A multi-site intercomparison of OC measurements was conducted at three Central European background stations, Melpitz (MEL), Frýdlant (FRY), and Košetice (NAOK), using aerosol mass spectrometry (AMS/ACSM) and thermal-optical transmission (TOT) methods (offline and semi-continuous). Semi-continuous and offline TOT measurements showed high consistency across sites and seasons, suggesting negligible influence of particle size differences on OC comparability. A pronounced seasonal contrast was observed between AMS derived OC (OC_AMS) and TOT based OC (OC_TOT). During summer, good agreement was found with OC_TOT:OC_AMS slopes of 1.27 (MEL), 0.86 (FRY), and 0.83 (NAOK). In winter, AMS systematically underestimated OC, with slopes decreasing to 0.34 (MEL), 0.24 (FRY), and 0.63 (NAOK). The discrepancy increased under combustion dominated conditions and was associated with low organic aerosol to equivalent black carbon (OA:eBC) ratios (<≈5), identifying a regime where OC_AMS and OC_TOT diverge substantially. Source dependent effects were evident, with the largest deviations observed at the coal influenced site (FRY) and during long-range transport events, while improved agreement coincided with higher OA:eBC ratios and enhanced secondary organic aerosol formation in summer. Evaluation of potential uncertainties (including pyrolytic carbon formation in TOT and AMS related limitations such as refractory organics and ionization efficiency) showed that no single factor explains the winter discrepancy, suggesting combined matrix and source effects. The results show that OA:eBC can serve as a practical indicator for OC_AMS-OC_TOT agreement and provide recommendations to improve OC quantification under winter combustion conditions.

Reliable quantification of organic carbon (OC) is essential for the comparability of long-term aerosol measurements across monitoring networks. A multi-site intercomparison of OC measurements was conducted at three Central European background stations, Melpitz (MEL), Frýdlant (FRY), and Košetice (NAOK), using aerosol mass spectrometry (AMS/ACSM) and thermal-optical transmission (TOT) methods (offline and semi-continuous). Semi-continuous and offline TOT measurements showed high consistency across sites and seasons, suggesting negligible influence of particle size differences on OC comparability. A pronounced seasonal contrast was observed between AMS derived OC (OC_AMS) and TOT based OC (OC_TOT). During summer, good agreement was found with OC_TOT:OC_AMS slopes of 1.27 (MEL), 0.86 (FRY), and 0.83 (NAOK). In winter, AMS systematically underestimated OC, with slopes decreasing to 0.34 (MEL), 0.24 (FRY), and 0.63 (NAOK). The discrepancy increased under combustion dominated conditions and was associated with low organic aerosol to equivalent black carbon (OA:eBC) ratios (<≈5), identifying a regime where OC_AMS and OC_TOT diverge substantially. Source dependent effects were evident, with the largest deviations observed at the coal influenced site (FRY) and during long-range transport events, while improved agreement coincided with higher OA:eBC ratios and enhanced secondary organic aerosol formation in summer. Evaluation of potential uncertainties (including pyrolytic carbon formation in TOT and AMS related limitations such as refractory organics and ionization efficiency) showed that no single factor explains the winter discrepancy, suggesting combined matrix and source effects. The results show that OA:eBC can serve as a practical indicator for OC_AMS-OC_TOT agreement and provide recommendations to improve OC quantification under winter combustion conditions.

Reliable quantification of organic carbon (OC) is essential for the comparability of long-term aerosol measurements across monitoring networks. A multi-site intercomparison of OC measurements was conducted at three Central European background stations, Melpitz (MEL), Frýdlant (FRY), and Košetice (NAOK), using aerosol mass spectrometry (AMS/ACSM) and thermal-optical transmission (TOT) methods (offline and semi-continuous). Semi-continuous and offline TOT measurements showed high consistency across sites and seasons, suggesting negligible influence of particle size differences on OC comparability. A pronounced seasonal contrast was observed between AMS derived OC (OCAMS) and TOT based OC (OCTOT). During summer, good agreement was found with OCTOT:OCAMS slopes of 1.27 (MEL), 0.86 (FRY), and 0.83 (NAOK). In winter, AMS systematically underestimated OC, with slopes decreasing to 0.34 (MEL), 0.24 (FRY), and 0.63 (NAOK). The discrepancy increased under combustion dominated conditions and was associated with low organic aerosol to equivalent black carbon (OA:eBC) ratios (<≈5), identifying a regime where OCAMS and OCTOT diverge substantially. Source dependent effects were evident, with the largest deviations observed at the coal influenced site (FRY) and during long-range transport events, while improved agreement coincided with higher OA:eBC ratios and enhanced secondary organic aerosol formation in summer. Evaluation of potential uncertainties (including pyrolytic carbon formation in TOT and AMS related limitations such as refractory organics and ionization efficiency) showed that no single factor explains the winter discrepancy, suggesting combined matrix and source effects. The results show that OA:eBC can serve as a practical indicator for OCAMS-OCTOT agreement and provide recommendations to improve OC quantification under winter combustion conditions.

L'exposition aux particules fines et ultrafines, pouvant contenir des éléments métalliques, est un sujet de préoccupation sanitaire majeure, notamment dans les zones fortement industrialisées. Cette thèse a consisté à mieux caractériser la fraction métallique des particules fines et ultrafines émises dans un contexte industrialo-urbain (Littoral dunkerquois) et à déterminer leur bioaccessibilité pulmonaire, en lien avec l'impact sanitaire. Des particules ont été collectées selon leur granulométrie dans des environnements très contrastés : (i) en milieu urbain sous l'influence du trafic automobile et d'émissions industrielles et (ii) à proximité immédiate et à la source même d'une usine de ferromanganèse (Glencore), caractéristique de l'activité industrielle du dunkerquois. La bioaccessibilité pulmonaire des éléménts métalliques a été déterminée par une extraction avec un fluide pulmonaire synthétique (solution "Gamble") et comparée avec une méthode d'extraction séquentielle. En milieu urbain, les concentrations élémentaires dans les particules ultrafines sont principalement liées aux sources locales (issues d'émissions de véhicules ou de chauffage). Les particules submicroniques (< 1µm) sont elles, principalement affectées par les sources industrielles, notamment la métallurgie, principale émettrice de métaux particulaires de la zone industrielle. Les autres sources identifiées par les traceurs métalliques sont la pétrochimie, la combustion des fiouls lourds et des charbons et les sources naturelles (terrigène et marine). Une variabilité temporelle importante des concentrations en masse des particules fines et ultrafines et de leurs teneurs en éléments métalliques a été observée, en cheminée et en champ proche de l'usine de ferromanganèse. Les fortes concentrations en particules ultrafines (PM₀,₁ : 60% de la masse des PM₂,₅), enrichies en métaux de cheminée, diminuent rapidement à proximité immédiate de l'usine, dû au changement rapide des conditions de température et d'humidité induisant des transformations précoces de la matière particulaire. Ce travail a permis par ailleurs de montrer que la bioaccessibilité des métaux associés aux particules est variable selon les propriétés physicochimiques des particules (spéciation chimique des métaux et distribution granulométrique), en lien avec leurs origines et leurs processus de formation. La bioaccessibilité des métaux peut aussi être affectée par des transformations physico-chimiques (mélange/agglomération, agrégation, oxydoréduction...) des particules fines durant leur transport atmosphérique. L'estimation in-vitro de la bioaccessibilité permet de mieux comprendre la biodosponibilité des métaux dans l'organiqme et donc de mieux appréhender l'impact sanitaire des métaux toxiques.

Open biomass burning (OBB) emits large amounts of air pollutants, significantly impacting air quality and climate change. Herein, chemical (carbonaceous content, metals, NR-PM ₁ : organics, SO ₄ ²⁻ , NO ₃ ⁻ , NH ₄ ⁺ , Cl ⁻ ) and physical (number size distribution, absorption and scattering) properties of OBB-derived aerosols, and their vertical distribution, and night-time evolution were investigated during the country-wide burning of the witches (BoW) in the Czech Republic and neighboring states. The mass concentrations of most of the aerosol components sharply increased during the BoW, and a fast change in their chemical composition, size distribution, and optical properties was observed. The BoW led to significantly higher concentrations of carbonaceous aerosols, with a concentration enhancement ratio ranging from 4.5 to 11.4. The vertical distribution of equivalent black carbon (eBC) was also altered during the BoW due to OBB emissions (eBC _BB ) contributing up to > 90% and 67% of eBC at 4 m and 230 m a.g.l., respectively. At 4 m, eBC _BB was affected by local OBB plumes trapped within the mixing layer, whereas eBC _BB at 230 m was most probably affected by longer distance transported plumes. Cl ⁻ and K, Zn, Pb and Cu were also significantly enhanced (2.6–10.8) due to OBB and coexisting sources (combustion of old tires and trash and fireworks activities). The freshest OBB emissions, made of 73% organics, with mobility diameter of 20 nm and 80 nm, rapidly grew during the first hours of the event with a single peak of ~ 100 nm. The higher concentrations of brown carbon led to an elevated absorption Ångström exponent (2.13 ± 0.26) and may also explain the enhanced scattering coefficients observed during this event. The BoW may significantly affect air quality and represents an excellent context to provide valuable background information on the physicochemical properties and night-time aging of non-heating OBB-derived aerosols in temperate climates. Graphical Abstract