A reliable determination of equivalent black carbon (eBC) mass concentrations derived from filter absorption photometers (FAPs) measurements depends on the appropriate quantification of the mass absorption cross-section (MAC) for converting the absorption coefficient (babs) to eBC. This study investigates the spatial-temporal variability of the MAC obtained from simultaneous elemental carbon (EC) and babs measurements performed at 22 sites. We compared different methodologies for retrieving eBC integrating different options for calculating MAC including: locally derived, median value calculated from 22 sites, and site-specific rolling MAC. The eBC concentrations that underwent correction using these methods were identified as LeBC (local MAC), MeBC (median MAC), and ReBC (Rolling MAC) respectively. Pronounced differences (up to more than 50 %) were observed between eBC as directly provided by FAPs (NeBC; Nominal instrumental MAC) and ReBC due to the differences observed between the experimental and nominal MAC values. The median MAC was 7.8 ± 3.4 m2 g-1 from 12 aethalometers at 880 nm, and 10.6 ± 4.7 m2 g-1 from 10 MAAPs at 637 nm. The experimental MAC showed significant site and seasonal dependencies, with heterogeneous patterns between summer and winter in different regions. In addition, long-term trend analysis revealed statistically significant (s.s.) decreasing trends in EC. Interestingly, we showed that the corresponding corrected eBC trends are not independent of the way eBC is calculated due to the variability of MAC. NeBC and EC decreasing trends were consistent at sites with no significant trend in experimental MAC. Conversely, where MAC showed s.s. trend, the NeBC and EC trends were not consistent while ReBC concentration followed the same pattern as EC. These results underscore the importance of accounting for MAC variations when deriving eBC measurements from FAPs and emphasize the necessity of incorporating EC observations to constrain the uncertainty associated with eBC.

Aix Marseille Univ CNRS LCE Marseille France

Aix Marseille Univ CNRS LCE Marseille France; Laboratory of Atmospheric Chemistry Paul Scherrer Institute 5232 Villigen Switzerland

Andalusian Institute for Earth System Research University of Granada Granada Spain

ARPA Lazio Regional Environmental Protection Agency Rome Italy

Arpa Lombardia Settore Monitoraggi Ambientali Unità Operativa Qualità dell'Aria Milano Italy

Atmospheric Composition Research Finnish Meteorological Institute Helsinki Finland

Atmospheric Pollution Laboratory Department of Applied Physics Miguel Hernández University Avenida de la Universidad S N 03202 Elche Spain

Center for Atmospheric Research University of Nova Gorica Nova Gorica 5270 Slovenia; Jozef Stefan Institute Ljubljana 1000 Slovenia

Department of Public Health Sciences University of Rochester School of Medicine and Dentistry Rochester NY USA; Institute for a Sustainable Environment Clarkson University Potsdam NY USA

Dept Atmospheric and Climate Research NILU Norwegian Institute for Air Research Kjeller Norway

Division of Air Resources New York State Dept of Environmental Conservation NY USA

Division of Environmental Health and Risk Management School of Geography Earth and Environmental Sciences University of Birmingham Edgbaston Birmingham United Kingdom; Department of Environmental Sciences Faculty of Meteorology Environment and Arid Land Agriculture King Abdulaziz University Jeddah Saudi Arabia

Environmental Radioactivity and Aerosol Technology for Atmospheric and Climate Impact Lab INRaSTES NCSR Demokritos Athens Greece

European Commission Joint Research Centre Ispra Italy

Helsinki Region Environmental Services Authority Helsinki Finland

Institut National de l'Environnement Industriel et des Risques Verneuil en Halatte France

Institute for Atmospheric and Earth System Research Physics Faculty of Science University of Helsinki Helsinki Finland

Institute for Environmental Research and Sustainable Development National Observatory of Athens Athens Greece

Institute of Atmospheric Sciences and Climate National Research Council Rome Italy

Institute of Environmental Assessment and Water Research Barcelona Spain

Institute of Environmental Assessment and Water Research Manresa Spain

Laboratoire des Sciences du Climat et de l'Environnement CEA Orme des Merisiers Gif sur Yvette France

Laboratory for Air Pollution and Environmental Technology Swiss Federal Laboratories for Materials Science and Technology Duebendorf Switzerland

Laboratory of Aerosols Chemistry and Physics Institute of Chemical Process Fundamentals Academy of Sciences of the Czech Republic Rozvojova Prague Czech Republic

Leibniz Institute for Tropospheric Research Leipzig Germany

MRC Centre for Environment and Health Environmental Research Group Imperial College London UK

MRC Centre for Environment and Health Environmental Research Group Imperial College London UK; HPRU in Environmental Exposures and Health Imperial College London UK

Saxon State Office for Environment Agriculture and Geology Saxon State Department for Agricultural and Environmental Operations Dresden Germany

Univ Grenoble CNRS IRD IGE 38000 Grenoble France

Citace poskytuje Crossref.org