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Discussion papers
https://doi.org/10.5194/acp-2018-1309
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2018-1309
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 Jan 2019

Research article | 09 Jan 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

Suzane S. de Sá1, Luciana V. Rizzo2, Brett B. Palm3,a, Pedro Campuzano-Jost3, Douglas A. Day3, Lindsay D. Yee4, Rebecca Wernis5, Gabriel Isaacman-VanWertz4,b, Joel Brito6,c, Samara Carbone6,d, Yingjun J. Liu1,e, Arthur Sedlacek7, Stephen Springston7, Allen H. Goldstein4, Henrique M. J. Barbosa6, M. Lizabeth Alexander8, Paulo Artaxo6, Jose L. Jimenez3, and Scot T. Martin1,9 Suzane S. de Sá et al.
  • 1John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
  • 2Department of Environmental Sciences, Universidade Federal de São Paulo, Diadema, São Paulo, Brazil
  • 3Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
  • 4Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
  • 5Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, California, USA
  • 6Institute of Physics, University of São Paulo, São Paulo, Brazil
  • 7Brookhaven National Laboratory, Upton, New York, USA
  • 8Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA
  • 9Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
  • anow at: Department of Atmospheric Sciences, University of Washington, Seattle, USA
  • bnow at: Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA
  • cnow at: IMT Lille Douai, Université Lille, SAGE, Lille, France
  • dnow at: Agrarian Sciences Institute, Federal University of Uberlândia, Minas Gerais, Brazil
  • enow at: College of Environmental Science and Engineering, Peking University, Beijing, China

Abstract. Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of submicron PM1 concentration, composition, and optical properties in central Amazonia during the dry season. The focus is on delineating the anthropogenic impact on the observed quantities, especially as related to the organic PM1. The primary study site was located 70km to the west of Manaus, a city of over two million people in Brazil. As part of the GoAmazon2014/5 experiment, datasets from a large suite of instrumentation were employed. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM1 composition, and aethalometer measurements were used to derive the absorption coefficient babs,BrC of brown carbon (BrC) at 370nm. The relationships of babs,BrC with AMS-measured quantities showed that the absorption was associated with less-oxidized, nitrogen-containing organic compounds. Atmospheric processing appeared to bleach the BrC components. The organic PM1 was separated into different classes by positive-matrix factorization (PMF). Estimates of the effective mass absorption efficiency associated with each PMF factor were obtained. Biomass burning and urban emissions appeared to contribute at least 80% of babs,BrC while accounting for 30 to 40% of the organic PM1 mass concentration. In addition, a comparison of organic PM1 composition between wet and dry seasons revealed that only a fraction of the nine-fold increase in mass concentration between the seasons was due to biomass burning. An eight-fold increase in biogenic secondary organic PM1 was observed. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Fuzzy c-means clustering identified three clusters to represent different pollution influences during the dry season, including baseline (dry season background, which includes biomass burning), event (increased influence of biomass burning and long-range transport of African volcanic emissions), and urban (Manaus influence on top of the background). The baseline cluster was associated with a mean mass concentration of 9 ± 3μgm−3. This concentration increased on average by 3μgm−3 for both the urban and the event clusters. The event cluster was characterized by remarkably high sulfate concentrations. Differences in the organic PM1 composition for the urban cluster compared to the other two clusters suggested a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season. 

Suzane S. de Sá et al.
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This study investigates the impacts of urbanization and fires in the Amazon on the concentration, composition, and optical properties of submicron particulate matter (PM1) in central Amazonia during the dry season. Biomass-burning and urban emissions appeared to contribute at least 80 % of brown carbon absorption while accounting for 30 to 40 % of the organic PM1 mass concentration. Only a fraction of the 9-fold increase in mass concentration relative to the wet season was due to biomass burning.
This study investigates the impacts of urbanization and fires in the Amazon on the...
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