81. A single-beam photothermal interferometer for in situ measurements of aerosol light absorptionBradley Visser, Jannis Röhrbein, Peter Steigmeier, Luka Drinovec, Griša Močnik, Ernest Weingartner, 2020, original scientific article Abstract: We have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.
Keywords: aerosol, aerosol absorption, black carbon, photo-thermal interferometer, climate change
Published in RUNG: 29.12.2020; Views: 2774; Downloads: 74
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83. Performance of microAethalometers: Real-world Field Intercomparisons from Multiple Mobile Measurement Campaigns in Different Atmospheric EnvironmentsHoney 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: 2806; Downloads: 184
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84. Photo-thermal interferometerLuka Drinovec, Griša Močnik, 2020, patent Abstract: A photo-thermal interferometer for measuring the light absorption of an aerosol or gas comprises a first laser source emitting a laser beam and a beam splitter adapted to divide the laser beam into a probe beam and a reference beam. The interferometer further comprises first optical elements which are adapted to direct the probe beam such that it passes through the aerosol and interferes with the reference beam thereafter thereby causing interference patterns. A detector detects the interference patterns. The interferometer further comprises a second laser source configured to emit a pump beam for transferring energy to the aerosol. Second optical elements are adapted to direct the pump beam such that it overlaps with the probe beam at least partially in the aerosol or gas. At least one of the second optical elements modifying the pump beam is an axicon.
Keywords: aerosol, absorption, black carbon
Published in RUNG: 15.09.2020; Views: 3111; Downloads: 0
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85. Air quality and climate change - how smart can the cities be?Griša Močnik, Matevž Lenarčič, 2020, unpublished invited conference lecture Abstract: What starts as an air quality problem in urban areas, ends up as a climate change problem globally. Emissions from cities and the power generating facilities powering the cities have local, regional and global effects. We show examples spanning these scales with very practical advice on how to start abatement locally.
Keywords: air quality, climate change, black carbon, aerosol, co2, smart city
Published in RUNG: 11.09.2020; Views: 3398; Downloads: 0
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86. The new instrument using a TC–BC (total carbon–black carbon) method for the online measurement of carbonaceous aerosolsMartin Rigler, Luka Drinovec, Gašper Lavrič, Anastasia Vlachou, André S. H. Prévôt, Jean-Luc Jaffrezo, Iasonas Stavroulas, Jean Sciare, Judita Burger, Irena Krajnc, Janja Turšič, Anthony D. A. Hansen, Griša Močnik, 2020, original scientific article Abstract: We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 µg C, which corresponds to a concentration of 0.3 µg C m−3 at a sample flow rate of 16.7 L min−1 and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer®, from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC–EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC=1.8, in the expected range.
Keywords: total carbon, aeroosl, black carbon, carbonaceous matter
Published in RUNG: 17.08.2020; Views: 3094; Downloads: 77
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87. Substantial brown carbon emissions from wintertime residential wood burning over FranceYunjiang Zhang, Alexandre Albinet, Jean-Eudes Petit, Véronique Jacob, Florie Chevrier, Gregory Gille, Sabrina Pontet, Eve Chrétien, Marta Dominik-Sègue, Gilles Levigoureux, Griša Močnik, Valérie Gros, Jean-Luc Jaffrezo, Olivier Favez, 2020, original scientific article Abstract: Brown carbon (BrC) is known to absorb light at subvisible wavelengths but its optical properties and sources are still poorly documented, leading to large uncertainties in climate studies. Here, we show its major wintertime contribution to total aerosol absorption at 370 nm (18–42%) at 9 different French sites. Moreover, an excellent correlation with levoglucosan (r2 = 0.9 and slope = 22.2 at 370 nm), suggesting important contribution of wood burning emissions to ambient BrC aerosols in France. At all sites, BrC peaks were mainly observed during late evening, linking to local intense residential wood burning during this time period. Furthermore, the geographic origin analysis also highlighted the high potential contribution of local and/or small-regional emissions to BrC. Focusing on the Paris region, twice higher BrC mass absorption efficiency value was obtained for less oxidized biomass burning organic aerosols (BBOA) compared to more oxidized BBOA (e.g., about 4.9 ± 0.2 vs. 2.0 ± 0.1 m2 g−1, respectively, at 370 nm). Finally, the BBOA direct radiative effect was found to be 40% higher when these two BBOA fractions are treated as light-absorbing species, compared to the non-absorbing BBOA scenario.
Keywords: Brown carbon, Multi sites, Residential wood burning, Mass absorption efficiency, France
Published in RUNG: 20.07.2020; Views: 3239; Downloads: 0
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89. Learning from Nature: Charge Transfer and Carbon Dioxide Activation at Single, Biomimetic Fe Sites in Tetrapyrroles on GrapheneManuel Corva, Fatema Mohamed, Erika Tomsič, Matteo Rinaldi, Cinzia Cepek, Nicola Seriani, Maria Peressi, Erik Vesselli, 2019, original scientific article Keywords: carbon dioxide, phthalocyanines, graphene, oxygen, Dirac cones
Published in RUNG: 03.12.2019; Views: 3416; Downloads: 0
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