Document Type

Article

Publication Date

2017

Publication Title

Atmospheric Chemistry and Physics

ISSN

1680-7324

Volume

17

Issue

3

DOI

http://dx.doi.org/10.5194/acp-17-1759-2017

Abstract

The occurrence of nonliquid and liquid physical states of submicron atmospheric particulate matter (PM) downwind of an urban region in central Amazonia was investigated. Measurements were conducted during two intensive operating periods (IOP1 and IOP2) that took place during the wet and dry seasons of the GoAmazon2014/5 campaign. Air masses representing variable influences of background conditions, urban pollution, and regional- and continental-scale biomass burning passed over the research site. As the air masses varied, particle rebound fraction, an indicator of physical state, was measured in real time at ground level using an impactor apparatus. Micrographs collected by transmission electron microscopy confirmed that liquid particles adhered, while nonliquid particles rebounded. Relative humidity (RH) was scanned to collect rebound curves. When the apparatus RH matched ambient RH, 95 % of the particles adhered as a campaign average. Secondary organic material, produced for the most part by the oxidation of volatile organic compounds emitted from the forest, produces liquid PM over this tropical forest. During periods of anthropogenic influence, by comparison, the rebound fraction dropped to as low as 60 % at 95 % RH. Analyses of the mass spectra of the atmospheric PM by positive-matrix factorization (PMF) and of concentrations of carbon monoxide, total particle number, and oxides of nitrogen were used to identify time periods affected by anthropogenic influences, including both urban pollution and biomass burning. The occurrence of nonliquid PM at high RH correlated with these indicators of anthropogenic influence. A linear model having as output the rebound fraction and as input the PMF factor loadings explained up to 70 % of the variance in the observed rebound fractions. Anthropogenic influences can contribute to the presence of nonliquid PM in the atmospheric particle population through the combined effects of molecular species that increase viscosity when internally mixed with background PM and increased concentrations of nonliquid anthropogenic particles in external mixtures of anthropogenic and biogenic PM.

Comments

A. P. Bateman (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
Z. Gong (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
T. H. Harder (Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA)
S. S. de Sá (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
B. Wang (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
P. Castillo (Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA)
S. China (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
Y. Liu (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
R. E. O'Brien (Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA)
B. B. Palm (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA)
H.-W. Shiu (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
G. G. Cirino (National Institute of Amazonian Research, Manaus, Amazonas, Brazil)
R. Thalman (Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA)
K. Adachi (Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute, Tsukuba, Ibaraki, Japan)
M. L. Alexander (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
P. Artaxo (Departamento de Física Aplicada, University of São Paulo, São Paulo, Brazil)
A. K. Bertram (Department of Chemistry, University of British Columbia, Vancouver, BC, Canada)
P. R. Buseck (School of Earth and Space Exploration & School of Molecular Sciences, Arizona State University, Tempe, AZ, USA)
M. K. Gilles (Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA)
J. L. Jimenez (Department of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA)
A. Laskin (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
A. O. Manzi (National Institute of Amazonian Research, Manaus, Amazonas, Brazil)
A. Sedlacek (Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA)
R. A. F. Souza (Amazonas State University, Manaus, Amazonas, Brazil)
J. Wang (Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA)
R. Zaveri (William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA)
S. T. Martin (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)

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Creative Commons Attribution 3.0 License
This work is licensed under a Creative Commons Attribution 3.0 License.

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