10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Chemical Composition of Ultrafine Particles in the Amazon Basin During GoAmazon2014/5
HAYLEY GLICKER, James Smith, Scot T. Martin, Suzane de Sá, University of California, Irvine
Abstract Number: 1029 Working Group: Remote/Regional Atmospheric Aerosol
Abstract While ultrafine (sub-100 nm diameter) particles have been observed in the Amazon Basin, the chemical processes that lead to their formation are not well understood. This is due to the lack of direct observations of boundary layer new particle formation as well as to the challenges in measuring ultrafine particle physico-chemical properties. The Amazon Basin is a unique environment with a climate that is highly sensitive to perturbations in aerosol particle properties and concentrations.(1) In addition, deforestation and urbanization are rapidly changing the Amazon’s environment, and the influence of these anthropogenic activities on ultrafine particles is largely unknown. This work focuses on characterizing the chemical composition of ultrafine particles and understanding the influence of both natural and anthropogenic sources on nanoparticle formation and growth processes in the Amazon Basin. These observations took place during the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) (2) campaign and feature measurements of ultrafine aerosol particle composition using the Thermal Desorption Chemical Ionization Mass Spectrometry (TDCIMS), as well as comparisons with other ground-based instruments deployed at the T3 site in Manacapuru, Brazil.
Our analysis focuses on a span of twelve days during the wet season, which featured a period with relatively clean air masses and a period with air masses that appear to have passed through Manaus, a large city of 1.8 million people. We identified the presence of compounds, such as 3-methylfuran and other IEPOX fragments, in the particle phase, that are indicators of a biogenic influence on ultrafine particle formation and growth. A fragment of an organic nitrogen compound, which we identify as NCO-, was the most abundant ion observed by the TDCIMS. This ion was also the most abundant ion observed in previous measurements by TDCIMS in a region impacted by emissions from the Mexico City Metropolitan Area. Sulfate was a minor constituent and did not exhibit a diurnal pattern, which suggests a long range transport source. During the period where air masses from Manaus were measured, there was less variability in the diurnal pattern of detected compounds but otherwise no significant difference in ion abundance compared to the clean, background period. The most abundant ions identified in ultrafine particles are compared to the potential sources determined from the analysis of backward trajectories obtained from an air parcel trajectory analysis using the HYSPLIT model.
References [1] Pöschl, U. et al. Rainforest Aerosols as Biogenic Nuclei of Clouds and Precipitation in the Amazon. Science 329, 1513-1516, doi:10.1126/science.1191056 (2010). [2] Martin, S. T. et al. Introduction: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5). Atmos. Chem. Phys. 16, 4785-4797, doi:10.5194/acp-16-4785-2016 (2016).