Document Type

Article

Publication Date

8-18-2018

Publication Title

Atmospheric Chemistry and Physics

ISSN

1680-7324

Volume

18

Issue

16

DOI

http://dx.doi.org/10.5194/acp-18-12185-2018

Abstract

An understanding of how anthropogenic emissions affect the concentrations and composition of airborne particulate matter (PM) is fundamental to quantifying the influence of human activities on climate and air quality. The central Amazon Basin, especially around the city of Manaus, Brazil, has experienced rapid changes in the past decades due to ongoing urbanization. Herein, changes in the concentration and composition of submicron PM due to pollution downwind of the Manaus metropolitan region are reported as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a suite of other gas- and particle-phase instruments were deployed at the T3 research site, 70 km downwind of Manaus, during the wet season. At this site, organic components represented 79±7 % of the non-refractory PM1 mass concentration on average, which was in the same range as several upwind sites. However, the organic PM1 was considerably more oxidized at T3 compared to upwind measurements. Positive-matrix factorization (PMF) was applied to the time series of organic mass spectra collected at the T3 site, yielding three factors representing secondary processes (73±15 % of total organic mass concentration) and three factors representing primary anthropogenic emissions (27±15 %). Fuzzy c-means clustering (FCM) was applied to the afternoon time series of concentrations of NOy, ozone, total particle number, black carbon, and sulfate. Four clusters were identified and characterized by distinct air mass origins and particle compositions. Two clusters, Bkgd-1 and Bkgd-2, were associated with background conditions. Bkgd-1 appeared to represent near-field atmospheric PM production and oxidation of a day or less. Bkgd-2 appeared to represent material transported and oxidized for two or more days, often with out-of-basin contributions. Two other clusters, Pol-1 and Pol-2, represented the Manaus influence, one apparently associated with the northern region of Manaus and the other with the southern region of the city. A composite of the PMF and FCM analyses provided insights into the anthropogenic effects on PM concentration and composition. The increase in mass concentration of submicron PM ranged from 25 % to 200 % under polluted compared with background conditions, including contributions from both primary and secondary PM. Furthermore, a comparison of PMF factor loadings for different clusters suggested a shift in the pathways of PM production under polluted conditions. Nitrogen oxides may have played a critical role in these shifts. Increased concentrations of nitrogen oxides can shift pathways of PM production from HO2-dominant to NO-dominant as well as increase the concentrations of oxidants in the atmosphere. Consequently, the oxidation of biogenic and anthropogenic precursor gases as well as the oxidative processing of preexisting atmospheric PM can be accelerated. This combined set of results demonstrates the susceptibility of atmospheric chemistry, air quality, and associated climate forcing to anthropogenic perturbations over tropical forests.

Comments

S. S. de Sá (School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA)
B. B. Palm (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA)
P. Campuzano-Jost (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA)
D. A. Day (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA)
W. Hu (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA)
G. Isaacman-VanWertz (Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA)
G. Isaacman-VanWertz (now at: Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA)
L. D. Yee (Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA)
J. Brito (Institute of Physics, University of São Paulo, São Paulo, Brazil)
J. Brito (now at: Laboratory for Meteorological Physics (LaMP), University Blaise Pascal, Aubière, France)
S. Carbone (Institute of Physics, University of São Paulo, São Paulo, Brazil)
S. Carbone (now at: Institute of Agricultural Sciences, Federal University of Uberlândia, Minas Gerais, Brazil)
I. O. Ribeiro (School of Technology, Amazonas State University, Manaus, Amazonas, Brazil)
G. G. Cirino (National Institute for Amazonian Research, Manaus, Amazonas, Brazil)
G. G. Cirino (now at: Department of Meteorology, Geosciences Institute, Federal University of Pará, Belém, Brazil)
Y. Liu (School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA)
Y. Liu (now at: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA)
R. Thalman (Brookhaven National Laboratory, Upton, New York, USA)
R. Thalman (now at: Department of Chemistry, Snow College, Richfield, Utah, USA)
A. Sedlacek (Brookhaven National Laboratory, Upton, New York, USA)
A. Funk (Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA)
C. Schumacher (Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA)
J. E. Shilling (Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington, USA)
J. Schneider (Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany)
P. Artaxo (Institute of Physics, University of São Paulo, São Paulo, Brazil)
A. H. Goldstein (Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA)
R. A. F. Souza (School of Technology, Amazonas State University, Manaus, Amazonas, Brazil)
J. Wang (Brookhaven National Laboratory, Upton, New York, USA)
K. A. McKinney (School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA)
K. A. McKinney (now at: Department of Chemistry, Colby College, Waterville, Maine, USA)
H. Barbosa (Institute of Physics, University of São Paulo, São Paulo, Brazil)
M. L. Alexander (Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA)
J. L. Jimenez (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA)
S. T. Martin (School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA)
S. T. Martin (Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA)

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This work is licensed under a Creative Commons Attribution 4.0 License.

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