Mass absorption cross section of black carbon for Aethalometer in the Arctic

Abstract

Long-term measurements of the mass concentration of black carbon (BC) in the atmosphere (M_BC) with well-constrained accuracy are indispensable to quantify its emission, transport, and deposition. The aerosol light absorption coefficient (b_abs), usually measured by a filter-based absorption photometer, including an Aethalometer (AE), is often used to estimate M_BC. The measured b_abs is converted to M_BC by assuming a value for the mass absorption cross section (MAC). Previously, we derived the MAC for AE (MAC (AE)) from measured b_abs and independently measured M_BC values at two sites in the Arctic. M_BC was measured with a filter-based absorption photometer with a heated inlet (COSMOS). The accuracy of the COSMOS-derived M_BC (M_BC (COSMOS)) was within about 15%. Here, we obtained additional MAC (AE) measurements to improve understanding of its variability and uncertainty. We measured b_abs (AE) and M_BC (COSMOS) at Alert (2018–2020), Barrow (2012–2022), Ny-Ålesund (2012–2019), and Pallas (2019–2022). At Pallas, we also obtained four-wavelength photoacoustic aerosol absorption spectrometer (PAAS-4λ) measurements of b_abs. b_abs (AE) and M_BC (COSMOS) were tightly correlated; the average MAC (AE) at the four sites was 11.4 ± 1.2 m² g⁻¹ (mean ± 1σ) at 590 nm and 7.76 ± 0.73 m² g⁻¹ at 880 nm. The spatial variability of MAC (AE) was about 11% (1σ), and its year-to-year variability was about 18%. We compared MAC (AE) in the Arctic with values at mid-latitudes, measured by previous studies, and with values obtained by using other types of filter-based absorption photometer, and PAAS-4λ.

Copyright © 2024 American Association for Aerosol Research

EDITOR:

• Hans Moosmüller

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgments

The authors thank Kevin Rawlings, Melody Fraser, and other technicians and contractors at Environment and Climate Change (Canada) and CFS Alert for the operation and maintenance of the Alert site and Ross Burgener and Bryan Thomas for the operation and maintenance of the Barrow site. MS and PRS sincerely acknowledge the Indian Institute of Space Science and Technology (IIST) for supporting this study as part of black carbon aerosol measurements between IIST and the National Institute of Polar Research (Japan) and the development of the IIST Ponmudi Climate Observatory. E. Andrews and the aerosol measurements at NOAA's Barrow Atmospheric Baseline Observatory were supported by a Department of Energy/Atmospheric Radiation Measurement User grant (ANL award no. 0F-60239).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT); Japan Society for the Promotion of Science KAKENHI Grants (JP20H00638); the Arctic Challenge for Sustainability II (ArCS II) project (JPMXD1420318865); the Environment Research and Technology Development Funds (JPMEERF20172003, JPMEERF20202003 and JPMEERF20232001) of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan; a grant for the Global Environmental Research Coordination System from Ministry of the Environment, Japan (MLIT2253); and by the research program “Changing Earth – Sustaining our Future” of the German Helmholtz Association. Measurements at Pallastunturi were supported by ACCC Flagship funding by the Academy of Finland (grant number 337552). The deployment of PAAS-4λ at the Pallas–Sodankylä Atmosphere–Ecosystem Supersite Facility is part of a project supported by the European Commission under the Horizon 2020 Research and Innovation Framework Program (H2020-INFRAIA-2020-1; grant no. 101008004).