Intercomparison and characterization of 23 Aethalometers under laboratory and ambient air conditions: Procedures and unit-to-unit variabilities

Abstract

Abstract. Airborne black carbon particles are monitored in many networks to quantify its impact on air quality and climate. Given its importance, measurements of black carbon mass concentrations must be conducted with instruments operating in a quality checked and assured conditions to generate reliable and comparable data. According to WMO (World Meteorological Organization) and GAW (Global Atmosphere Watch), intercomparisons against a reference instrument are a crucial part of quality controls in measurement activities (WMO, 2016). The WMO-GAW World Calibration Centre for Aerosol Physics (WCCAP) carried out several instrumental comparison and calibration workshops of absorption photometers in the frame of ACTRIS (European Research Infrastructure for the observation of Aerosol, Clouds and Trace Gases) and the COST Action COLOSSAL (Chemical On-Line cOmpoSition and Source Apportionment of fine aerosoL) in January and June 2019. The experiments were conducted to intercompare filter-based particle light absorption photometers, specifically aethalometers AE33 (Magee Scientific), which are operated by research institutions, universities or governmental entities across Europe. The objective was to investigate the individual performance of 23 instruments and their comparability, using synthetic aerosols in a controlled environment and ambient air from the Leipzig urban background. The methodology and results of the intercomparison are presented in this work. The observed instrument-to-instrument variabilities showed differences that were evaluated, before maintenance activities (average deviation from total least square regression: 1.1 %, range: −6 % to 16 %, for soot measurements; average deviation: 0.3 %, range: −14 % to 19 %, for nigrosin measurements), and after they were carried out (average deviation: 0.4 %, range: −8 % to 14 %, for soot measurements; average deviation: 1.1 %, range: −15 % to 11 %, for nigrosin measurements). The deviations are in most of the cases explained by the filter material, the total particles load on the filter, the performance of the flow systems and previous flow check and calibrations carried out with non-calibrated devices. The results of this intensive intercomparison activity show that relatively small unit-to-unit uncertainties of AE33-based particle light absorbing measurements are possible with functioning instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to assure high quality and comparable BC measurements among international observational networks.

Variations in Black Carbon concentration and sources during COVID-19 lockdown in Delhi

“…The instrument used in the present study is well maintained and calibrated, the flow test, leakage test, sampling spot test, optical chamber cleaning and inlet cleaning were performed periodically as per the user manual of the instrument. These parameters directly influence accuracy of the instrument ( Cuesta et al., 2020 ).…”

Long-Term eBC Measurements with the Use of MAAP in the Polluted Urban Atmosphere (Poland)

“…The study also examined the relationship of eBC concentrations with meteorological parameters and concentrations of selected gaseous pollutants, which allowed for preliminary identification of factors influencing air pollution by black carbon, including preliminary determination of possible sources of BC emission. The introduction of eBC measurements with the use of automatic devices will allow the improvement of the air quality monitoring network in Poland, similar to many regions in Europe [16,24,25].…”

Office Indoor PM and BC Level in Lithuania: The Role of a Long-Range Smoke Transport Event

“…The channel at 880 nm was used for equivalent black carbon (eBC) mass concentration and default fixed mass absorption cross-section (MAC) (16.6 m 2 g −1 ) was used for the evaluation. Uncertainties evaluated during intercomparison campaigns were applied to the aethalometer (10% [35]) and APS measurements (10% [36]). A nephelometer (TSI model 3563) was used to measure outdoor environment only.…”