Determination of Aethalometer multiple-scattering enhancement parameters and impact on source apportionment during the winter 2017–2018 EMEP/ACTRIS/COLOSSAL campaign in Milan

Bernardoni, V.; Ferrero, Luca; Bolzacchini, Ezio; Forello, Alice Corina; Gregorič, Asta; Massabò, Dario; Močnik, Griša; Prati, P.; Rigler, Martin; Santagostini, Luca; Soldan, Francesca; Valentini, Sara; Valli, G.; Vecchi, R.

doi:10.5194/amt-2020-233

Cited by 2 publications

(4 citation statements)

References 38 publications

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“…S3). The values of the C factor for the AE33 TFE-coated glass and M8060 filter tapes obtained at urban background stations in Rome (Valentini et al, 2020a) and Leipzig (Müller, 2015;Bernardoni et al, 2020) were in the same range as those found in this work for BCN (Table 1).…”

Section: Multiple Scattering Correction Factor: Average Values and Sesupporting

confidence: 81%

“…Moreover, a wavelength-dependent C factor can have an impact on aethalometer based BC source apportionment analysis, such as the Aethalometer model, used to determine the contribution from fossil fuels vs biomass burning emissions (Sandradewi et al, 2008). Weingartner et al (2003) and Segura et al (2014) found no wavelength dependence for the multiple scattering parameter C for older versions of aethalometer (model AE31), whereas Bernardoni et al (2020) found a decrease of the C factor with wavelengths, although not statistically significant, and reported the impact of the wavelength dependent C on source apportionment model results. Virkkula et al (2015) and Drinovec et al (2017) have shown that the AE33 factor loading parameter, k, increases with increasing BF (smaller particles) and decreases with increasing SSA and that the wavelength dependence of k also depends on these two optical properties.…”

Section: Wavelength Dependence Analysis From the Pp_unimi Vs Ae33 Commentioning

confidence: 99%

“…larger by a factor of 1.64 (Müller, 2015;WMO, 2016); for the AE33 Drinovec et al (2015) found a C of 1.57 for the Pallfex Teflon-coated glass fiber (TFE-coated glass), which, after re-normalization using the factor 1.64, resulted in C=2.57. Moreover, different experimental C factor values have been obtained ranging between 2.57-4.24 (Müller et al, 2011b;Drinovec et al, 2020;Laing et al, 2020;Valentini et al, 2020a;Bernardoni et al, 2020). In addition, these filters have been found to feature a crosssensitivity to scattering, m s , ranging between 1 and 5% (Müller, 2015;Drinovec et al, 2015;Zhang et al, 2018;Corbin et al, 2018;Laing et al, 2020;Drinovec et al, 2020).…”

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confidence: 99%

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Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: A multi-instrumental approach

Yus-Díez¹,

Bernardoni²,

Močnik³

et al. 2021

Preprint

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Abstract. Accurate measurements of light absorption by aerosolized particles, especially black carbon (BC), are of utter importance since BC represents the second most important climate-warming agent after carbon dioxide (CO2). Reducing the uncertainties related to the absorption measurement techniques will improve the global estimation of BC concentration and the radiative effects of light absorbing aerosols. Currently, one of the most widely used instruments for BC and absorption measurements is the dual-spot aethalometer, AE33, which derives the absorption coefficients of aerosol particles at 7 different wavelengths from the measurements of optical attenuation through a filter where particles are continuously collected. An accurate determination of the absorption coefficient relies on the quantification of non-linear processes related to the collection of sample on the filter. The multiple-scattering correction factor (C(λ)), which depends on the filter tape used and on the optical properties of the collected particles, is the parameter with the greatest uncertainty.An in-depth analysis of the AE33 multiple-scattering correction factor and its wavelength dependence for different filter tapes, i.e. the old most referenced known as TFE-coated glass and the current most widely used M8060, has been carried out by comparing the AE33 attenuation measurements with the absorption measurements from different filter-based techniques. Online co-located multi-angle absorption photometer (MAAP) measurements and offline PP_UniMI polar photometer measurements were used with this aim. We used data from three different measurement stations in North-East of Spain: an urban background station (Barcelona; BCN), a regional background station (Montseny; MSY) and a mountain-top station (Montsec d'Ares; MSA). The median C values (at 637 nm) measured at the three stations ranged between 2.29 (at BCN and MSY; lowest 5th percentile of 1.97 and highest 95th percentile of 2.68) and 2.51 (at MSA; lowest 5th percentile of 2.06 and highest 95th percentile of 3.06). The C factor was wavelength-dependent only at the mountain-top station, whereas at the urban and regional stations no statistically significant difference was found at the 7 different AE33 wavelengths. The wavelength-dependence of C at the mountain station was in part driven by the predominant effect of dust particles during Saharan dust outbreaks at this station. At the mountain station, neglecting the wavelength dependence of the C factor led to an underestimation of the Absorption Ångström Exponent (AAE) of 12 %. The analysis of the cross-sensitivity to scattering for different filter tapes revealed a large increase of the C factor at the three stations when the single scattering albedo (SSA) of the collected particles was above 0.90–0.95, with up to a 3-fold increase above the average values. The result of the cross-sensitivity to scattering displayed a fitted constant multiple scattering parameter, Cf, of 2.21 and 1.96 and a cross-sensitivity factor, ms, of 0.8 % and 1.7 % for MSY and MSA stations, respectively, for the TFE-coated glass filter tape. For the M8060 filter tape, Cf of 2.50, 1.96, 1.82 and a ms of 0.7 %, 1.5 %, 2.7 %, for BCN, MSY and MSA stations, respectively, were obtained. Differences in the absorption coefficient determined from AE33 measurements at BCN, MSY and MSA of around a 35–40 % can be expected when using the site-dependent C determined experimentally instead of the nominal C value.

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Section: Multiple Scattering Correction Factor: Average Values and Sesupporting

confidence: 81%

Section: Wavelength Dependence Analysis From the Pp_unimi Vs Ae33 Commentioning

confidence: 99%

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confidence: 99%

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Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: A multi-instrumental approach

Yus-Díez¹,

Bernardoni²,

Močnik³

et al. 2021

Preprint

Self Cite

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“…Most commonly a constant value is used appropriate for the instrument and filter material. It is to be noted that the Cref value can have a large variability depending on seasons, location, and methodology of determination (Collaud Coen et al, 2010;Backman et al, 2017;Di Biagio et al, 2017;Bernardoni et al, 2021;. The scattering correction requires measurement of the scattering coefficient which in many cases is not possible due to the lack of instrumentation and this correction is assumed to be unity as in this study.…”

Section: Measurement Methodsmentioning

confidence: 99%

Applicability of small-scale black carbon sensors to explore high resolution spatial variability of ambient black carbon

Elomaa,

Luoma,

Harni

et al. 2024

Preprint

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Abstract. Black Carbon (BC) is a particulate pollutant emitted as a by-product of combustion. BC has an emerging role in air quality monitoring with the current recommendations by the World Health Organization, that systematic measurements of BC should be conducted to capture the temporal and spatial variability of BC. To observe this variability, especially in urban areas, a large quantity of sensor-type measurements is required. In this study, four different types of small-scale filter-based BC sensors (AE51, MA200, MA350, Observair) were used to build a sensor network in Kumpula campus, Helsinki, Finland. Our aim was to test the applicability of the sensors to monitor ambient BC concentrations in field conditions and to study the variation of BC in high resolution. The results were compared to a reference level instrument (MAAP) for validation. During intercomparisons, the sensors had a good correlation with the reference and after a simple orthogonal regression calibration, were deemed suitable for deployment in the sensor network. During deployment, the sensor network proved to be able to capture small scale temporal and spatial differences in BC concentrations and showed potential for source-apportionment applications. The changes in temperature (T) and relative humidity (RH) were observed to induce error in the BC measurements. This error was amplified by the dualspot correction, which was worsening the measurement result under instable conditions of T and RH. This should be considered when using sensors that apply this correction automatically. The environmental compensation used by the Observair sensors reduced the error from the changing T and RH. To reduce the effect of changing T and RH, more robust environmentally controlled boxes should be developed or correction algorithms, such as environmental compensation, should be applied.

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Determination of Aethalometer multiple-scattering enhancement parameters and impact on source apportionment during the winter 2017–2018 EMEP/ACTRIS/COLOSSAL campaign in Milan

Cited by 2 publications

References 38 publications

Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: A multi-instrumental approach

Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: A multi-instrumental approach

Applicability of small-scale black carbon sensors to explore high resolution spatial variability of ambient black carbon

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