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Volume 17, issue 3 | Copyright

Special issue: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5)...

Atmos. Chem. Phys., 17, 1759-1773, 2017
https://doi.org/10.5194/acp-17-1759-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Feb 2017

Research article | 06 Feb 2017

Anthropogenic influences on the physical state of submicron particulate matter over a tropical forest

Adam P. Bateman1, Zhaoheng Gong1, Tristan H. Harder2,a, Suzane S. de Sá1, Bingbing Wang3,4, Paulo Castillo5, Swarup China3, Yingjun Liu1, Rachel E. O'Brien2,b, Brett B. Palm6, Hung-Wei Shiu3,c, Glauber G. Cirino7, Ryan Thalman5,d, Kouji Adachi8, M. Lizabeth Alexander3, Paulo Artaxo9, Allan K. Bertram10, Peter R. Buseck11, Mary K. Gilles2, Jose L. Jimenez6, Alexander Laskin3, Antonio O. Manzi7, Arthur Sedlacek5, Rodrigo A. F. Souza12, Jian Wang5, Rahul Zaveri3, and Scot T. Martin1,13 Adam P. Bateman et al.
  • 1School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 2Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
  • 3William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
  • 4State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
  • 5Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA
  • 6Department of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
  • 7National Institute of Amazonian Research, Manaus, Amazonas, Brazil
  • 8Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute, Tsukuba, Ibaraki, Japan
  • 9Departamento de Física Aplicada, University of São Paulo, São Paulo, Brazil
  • 10Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
  • 11School of Earth and Space Exploration & School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
  • 12Amazonas State University, Manaus, Amazonas, Brazil
  • 13Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
  • anow at: Physikalisches Institut, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
  • bnow at: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
  • cnow at: Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan 30076
  • dnow at: Departments of Chemistry and Natural Resources, Snow College, Richfield, UT, USA

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.

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The occurrence of nonliquid and liquid physical states of submicron atmospheric particulate matter (PM) downwind of an urban region in central Amazonia was investigated. Air masses representing background conditions, urban pollution, and regional- and continental-scale biomass were measured. Anthropogenic influences contributed to the presence of nonliquid PM in the atmospheric particle population, while liquid PM dominated during periods of biogenic influence.
The occurrence of nonliquid and liquid physical states of submicron atmospheric particulate...
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