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The Contribution of Black Carbon and Non-BC Absorbers to the Aerosol Absorption Coefficient in Nanjing, China

Category: Urban Air Quality

Volume: 20 | Issue: 3 | Pages: 590-605
DOI: 10.4209/aaqr.2019.06.0326
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To cite this article:
Leskinen, A., Ruuskanen, A., Kolmonen, P., Zhao, Y., Fang, D., Wang, Q., Gu, C., Jokiniemi, J., Hirvonen, M.R., Lehtinen, K.E., Romakkaniemi, S. and Komppula, M. (2020). The Contribution of Black Carbon and Non-BC Absorbers to the Aerosol Absorption Coefficient in Nanjing, China. Aerosol Air Qual. Res. 20: 590-605. doi: 10.4209/aaqr.2019.06.0326.

Ari Leskinen 1,2, Antti Ruuskanen1, Pekka Kolmonen1, Yu Zhao3, Die Fang3, Qingeng Wang3, Cheng Gu3, Jorma Jokiniemi4, Maija-Riitta Hirvonen4, Kari E.J. Lehtinen1,2, Sami Romakkaniemi1, Mika Komppula1

  • 1 Finnish Meteorological Institute, Yliopistonranta 1 F, FI-70210 Kuopio, Finland
  • 2 Department of Applied Physics, University of Eastern Finland, Yliopistonranta 1 F, FI-70210 Kuopio, Finland
  • 3 School of the Environment, Nanjing University, Nanjing 210023, China
  • 4 Department of Environmental and Biological Science, University of Eastern Finland, Yliopistonranta 1 F, FI-70210 Kuopio, Finland

Highlights

  • Aerosol absorption coefficient was monitored for a year in Nanjing, China.
  • Black and brown carbon contributions to absorption were estimated with two methods.
  • The two methods were found to agree well for long-term averages.
  • Variation between the two methods was found in more detailed analysis.
  • Biomass burning was found as one source of brown carbon.

Abstract

An aethalometer was employed in a 1-year campaign (November 2014–November 2015) in Nanjing, China, that aimed to estimate the contributions of black carbon (BC; annual average ± std = 4.0 ± 3.3 µg m–3) and non-BC absorbers, such as brown carbon, to the aerosol absorption coefficient. We applied two methods: 1) the traditional calculation from the aethalometer data, assuming an absorption Ångström exponent (AAE) of unity for BC (“AE method”), which provided an overall average of 27.2% for the non-BC contribution, and 2) a recently developed method based on the wavelength dependence of AAE (the “WDA method”), which indicated the existence of non-BC absorbers in 25.3% of the samples on average. We utilized trajectory and source area analyses and, in agreement with the results from other studies in this region, verified biomass burning emission sources, mainly to the northwest of the measurement site.

Keywords

Aethalometer Mie calculation Trajectory analysis Source area analysis


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