Performance of microAethalometers: Real-world Field Intercomparisons from Multiple Mobile Measurement Campaigns in Different Atmospheric Environments

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 (R 2 > 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 (R 2 > 0.8, slope ≈ 1.0), AE51(R 2 > 0.9, slope ≈ 0.9), and a stationary Aethalometer (AE33) across all wavelengths (R 2 > 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.

The impact of temperature inversions on black carbon and particle mass concentrations in a mountainous area

“…The mobile measurements were done using the TROPOS aerosol backpack equipped with portable instruments (Alas et al, 2019a(Alas et al, , 2019bAlas et al, 2020). On top of the backpack, the aerosol is sampled with 1 m long stainless steel inlet.…”

“…The run in the morning lasted from 6:30 to 9:00, at noon from 12:00 to 14:00 and in the evening from 17:00 to 19:00 LT. To obtain representative information, daily measurements along the depression were conducted 107 times, totalling to 642 km. Results of the convergence analysis (see Alas et al, 2020 and the reference therein for the assessment process) for all data points in the Retje village and at Tabor hill are depicted in Fig. S12.…”

“…In order to acquire highly resolved spatial and temporal data, mobile measurements have been increasingly used in air quality monitoring, predominantly in urban areas (e.g. Alas et al, 2019aAlas et al, , 2019bAlas et al, , 2020 and the reference therein), yet rarely in hilly/mountainous rural regions (for instance Weimer et al, 2009).…”

“…Besides diesel dominated aerosols, the selected value of k is representative for freshly emitted particles from wood burning as well. Detection of the filter-loading effect, correction, and correlation between the microAethalometers AE51 against reference instruments (the AE33 Aethalometers) used in the Loški Potok campaign are published inAlas et al, 2020.…”

Black Carbon in Bulgaria—Observed and Modelled Concentrations in Two Cities for Two Months

“…Filter-based optical methods for estimation of BC concentration suffer from two major artifacts-the filter loading (or shadowing) effect and the multiple scattering effect [51][52][53][54][55][56][57][58][59]. The filter loading effect (FLE) is a bias that affects the apparent concentrations relative to the ambient ones.…”