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Major influence of secondary organic aerosol to lensing effect black carbon absorption enhancement

Abstract : Atmospheric black carbon (BC) and light-absorbing organic aerosol (also referred as brown carbon, BrC) have strong effects on the Earth’s climate by absorbing direct solar radiation. A better understanding of specific underlying mechanisms is still needed to parametrize the influence of primary emissions and secondary processes on absorption properties. In particular, BC absorption enhancement (Eabs) due to internal mixing with other chemical species - so-called lensing effect - is poorly assessed, due to the lack of long-term in situ measurements of both the optical and chemical properties of BC-containing particles. Here, we report results of a three-year continuous field observations conducted from March 2014 to March 2017 at a suburban background station (SIRTA) in the Paris region (France). Submicron nonrefractory aerosol species were measured in near real-time using an aerodyne aerosol chemical speciation monitor (ACSM) and were apportioned using Positive Matrix Factorization (PMF) analysis to identify and quantified major organic aerosol (OA) sources. Light absorption properties of BC and BrC were determined by direct measurements using a 7-wavelength aethalometer equipped with the dual spot technology. Important BrC contribution to the total absorption in the near UV could be attributed to residential wood burning activities in winter and led to significant Eabs, independently of internal or external BrC mixing with BC particles. Co-located 24-hy filter-based analyses were also performed by thermo-optical technique to quantify the mass concentration of elemental carbon (EC) in PM2.5. Absorption enhancement (Eabs) of BC-containing particles was obtained using mass absorption coefficient (MAC) ratios calculated between observed (= babs / [EC]) and expected values for uncoated BC. Results showed that the observed Eabs significantly increased with the mass ratio of secondary aerosols to EC, indicating a strong influence of this secondary components on BC absorption enhancement. These findings suggest that SOA could represent one of the most critical chemical species to be considered within climate models.
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Submitted on : Wednesday, May 26, 2021 - 6:11:05 PM
Last modification on : Friday, October 14, 2022 - 9:05:35 AM


  • HAL Id : ineris-03237723, version 1


Olivier Favez, Yunjiang Zhang, Alexandre Albinet, Francesco Canonaco, André Prevot, et al.. Major influence of secondary organic aerosol to lensing effect black carbon absorption enhancement. 12. International conference on carbonaceous particles in the atmosphere (ICCPA), Apr 2019, Vienne, Austria. pp.153. ⟨ineris-03237723⟩



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