10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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The Role of Biological Particles in the Amazon Rainforest
SWARUP CHINA, Susannah Burrows, Marje Prank, Daniel Veghte, Bingbing Wang, Johannes Weis, Natalie Mahowald, Daniel Knopf, Mary Gilles, Alexander Laskin, Pacific Northwest National Laboratory
Abstract Number: 1033 Working Group: Aerosol Chemistry
Abstract The Amazon basin is the largest rainforest on Earth, and therefore plays a major role in global biogeochemical cycles as well as the global water cycle. Improved understanding of the Amazon rainforest’s interactions with the atmosphere is therefore a topic of interest. These interactions the particulates emitted from, and deposited to the Amazon rainforest, as players in global nutrient transport and as sources of cloud condensation and ice nuclei. Locally emitted biological particles dominate the coarse mode aerosol particle population in the basin. Particles with mixed sodium salts observed in the area are commonly attributed to marine aerosols transported from the Atlantic Ocean. Here, using detailed chemical imaging analysis and modeling studies, we show that biological particles emitted by the forest biosphere are a major source of sodium-containing particles observed in the central Amazon basin, likely the dominant source of particulate sodium during the wet season. Furthermore, we show that a significant fraction of biological particles is internally mixed with submicron- to micron-sized dust particles. Dynamic microscopic observations of ice nucleation events on individual biological-dust particles reveal that water uptake and ice formation is initiated by the dust inclusions of the mixed biological-dust particle rather than the carbonaceous material of biological particles. Our results suggest that dust inclusions may plausibly impact cold cloud formation in Amazonia and thus influence the cloud microphysics and hydrological cycle in the Amazon basin.