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Spectral absorption of brown carbon in the Central Amazonia
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  • Fernando Morais,
  • Paulo Artaxo,
  • Henrique Barbosa,
  • Marco Aurélio Franco,
  • Bruna Holanda,
  • Djacinto dos Santos,
  • Delano Campos,
  • Eduardo Landulfo,
  • Christopher Pöhlker,
  • Jose Martins
Fernando Morais
University of São Paulo
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Paulo Artaxo
University of Sao Paulo

Corresponding Author:artaxo@if.usp.br

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Henrique Barbosa
University of São Paulo
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Marco Aurélio Franco
University of São Paulo
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Bruna Holanda
Max Planck Institute for Chemistry
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Djacinto dos Santos
University of São Paulo
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Delano Campos
Max Planck Institute for Chemistry
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Eduardo Landulfo
IPEN Nuclear Energy Research Institute
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Christopher Pöhlker
Max Planck Institute for Chemistry
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Jose Martins
Earth and Space Institute, UMBC
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Abstract

There is a need to better characterize aerosol absorption due to its remarkable radiative effects on climate. In particular, we need to understand the separation of total absorption between the two main components, the black carbon (BC) and brown carbon (BrC), especially in places where the anthropic influence is little, such as in pristine regions like Central Amazonia. The mechanisms that control the formation and evolution of BC and BrC in tropical forests remain unclear. In this study, we have performed detailed measurements at the Amazon Tall Tower Observatory (ATTO) tower on aerosols collected in Nuclepore filters and analyzed them with high-resolution optical spectrometers with a wide spectral range (300 to 2500 nm). Thus, we determined the absorption characteristics of BrC as a function of wavelength. The results show that BrC absorption is spectrally significant below 660 nm and is maximum at wavelengths close to 370 nm. Combining the measured spectral dependency with MIE modeling of the BC contribution, we determined that the BrC accounts for 14.8% of the total absorption. A similar fraction of BrC to total absorption was obtained through a similar analysis of in-situ measurements. Elemental chemical analysis of the filters, cluster, and factor analysis shows that the BrC is associated with airborne dust. The different methods to quantify BC and BrC are consistent and show similar results. This study will allow the quantification of the role of BrC and BC in aerosol absorption of radiation in Amazonia.