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Recommendations for reporting equivalent black carbon (eBC) mass concentrations based on long-term pan-European in-situ observations
Marjan Savadkoohi, Marco Pandolfi, Olivier Favez, Jean-Philippe Putaud, Konstantinos Eleftheriadis, Markus Fiebig, Philip Hopke, Paolo Laj, A. Wiedensohler, Griša Močnik, 2024, original scientific article

Abstract: 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 regression 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 from 12 aethalometers at 880 nm, and 10.6 ± 4.7 m2/g 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 emphasizes the necessity of incorporating EC observations to constrain the uncertainty associated with eBC.
Keywords: equivalent black carbon, mass absorption cross-section, filter absorption photometers, elemental carbon, absorption, site specific MAC, rolling MAC
Published in RUNG: 04.03.2024; Views: 591; Downloads: 4
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Hidden black carbon air pollution in hilly rural areas - a case study of Dinaric depression
Kristina Glojek, Asta Gregorič, Griša Močnik, Andrea Cuesta-Mosquera, A. Wiedensohler, Luka Drinovec, Matej Ogrin, 2020, original scientific article

Abstract: Air pollution is not an exclusively urban problem as wood burning is a widespread practice in rural areas. As we lack information on the air quality situation in rural mountainous regions, our aim is to examine equivalent black carbon (eBC) pollution in a typical rural karst area in the settlement of Loški Potok (Slovenia). eBC mass concentrations were measured by Aethalometer (AE-33) at two sites in Retje karst depression. The rural village station was located at the bottom of the karst depression whereas the rural background station was positioned at the top of the hill. We showthe diurnal variation of equivalent black carbon mass concentrations for different seasons. In the populated karst depression, the major source of eBC pollution are households using wood as a heating fuel reaching the highest mass concentrations in winter. Diurnal pattern of eBC from biomass burning and traffic differ due to different source activity and it is influenced by typical formation of a cold air pool from late afternoon until late morning, restricting the dispersion of local emissions. The large difference in mass concentrations between the lowest part of the village (rural station) and the top of the hill (rural background station) indicates that in a vertically stratified and stable atmosphere local sources of black carbon have a major impact onair quality conditions in the area studied. Since in Alpine and Dinaric regions there are many similar inhabited areas, we can expect similar air quality conditions also in other rural hilly areas with limited self-cleaning air capacity.
Keywords: air pollution, black carbon, hidden geographies, diurnal variation, biomass burning, relief depressions, Loški Potok, Slovenia
Published in RUNG: 04.01.2021; Views: 2555; Downloads: 0
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Performance of microAethalometers: Real-world Field Intercomparisons from Multiple Mobile Measurement Campaigns in Different Atmospheric Environments
Honey Alas, Thomas Mueller, Kay Weinhold, Sascha Pfeifer, Kristina Glojek, Asta Gregorič, Griša Močnik, Luka Drinovec, Francesca Costabile, Martina Ristorini, A. Wiedensohler, 2020, original scientific article

Abstract: Small aethalometers are frequently used to measure equivalent black carbon (eBC) mass concentrations in the context of personal exposure and air pollution mapping through mobile measurements (MM). The most widely used is the microAethalometer (AE51). Its performance in the laboratory and field is well documented, however, there is not sufficient data in the context of its performance in different environments. In this investigation, we present the characterization of the performance of the AE51 through field unit-to-unit intercomparisons (IC), and against a reference absorption photometer from three MM campaigns conducted in drastically different environments. Five IC parameters were considered: i) study area, ii) location of IC, iii) time of day, iv) duration of IC, and v) correction for the filter-loading effect. We can conclude that it is crucial where and how long the IC have been performed in terms of the correlation between the mobile and reference instruments. Better correlations (R2 > 0.8, slope = 0.8) are achieved for IC performed in rural, and background areas for more than 10 minutes. In locations with more homogenous atmosphere, the correction of the loading effect improved the correlation between the mobile and reference instruments. In addition, a newer microAethalometer model (MA200) was characterized in the field under extreme cold conditions and correlated against another MA200 (R2 > 0.8, slope ≈ 1.0), AE51(R2 > 0.9, slope ≈ 0.9), and a stationary Aethalometer (AE33) across all wavelengths (R2 > 0.8, slope ≈ 0.7). For MA200, the loading effect was more pronounced, especially at the lower wavelengths, hence the correction of the loading effect is essential to improve the correlation against the AE33. The MA200 and AE51 proved to be robust and dependable portable instruments for MM applications. Real-world quality assurance of these instruments should be performed through field IC against reference instruments with longer durations in areas of slowly changing eBC concentration.
Keywords: Portable instruments, Mobile monitoring, Black carbon, Instrument intercomparisons
Published in RUNG: 15.09.2020; Views: 2848; Downloads: 184
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