GOAMAZON-AMS

Observations and Modeling of the Green Ocean Amazon: Aerosol Mass Spectrometry

15 January 2014 - 31 December 2014

Lead Scientist: Lizabeth Alexander

Observatory: AMF , MAO

The first objective of the proposed project was to understand and quantify the interactions of biogenic and anthropogenic emissions with respect to the production of secondary organic aerosol (SOA). In clean conditions in the Amazon basin, SOA dominates the diameter distribution of the submicron particles. How and why is the diameter distribution shifted by pollution? The second objective follows from the first in that, although the diameter distribution is dominated by SOA, the actual source of new particle production remains uncertain (i.e., the number concentration). The second objective was to test the hypothesis that new particles under natural conditions are produced as a result of evaporation of primary particles emitted by fungal spores as well as to investigate any shifts in this mechanism under pollution conditions, e.g., in consequence to the high concentrations of SO2 in the pollution plume. Combined, the number-diameter distribution is the key connection to upscaling to the effects of aerosol particles on clouds and climate. Understanding this upscaling under clean and pollution conditions, including differences, is the third objective. EMSL provided its high resolution aerosol mass spectrometry, or AMS, capability for the field campaign and associated user facility support for the entire year of 2014, focused on addressing the first and second objectives described above. The AMS quantitatively measures the size and chemical composition of volatile/semi-volatile submicron aerosols. It is designed to provide quantitative composition information on ensembles of particles. Therefore the deployment of the EMSL AMS provided an unprecedented continuous data set of size and composition of aerosol particles produced over the range of conditions represented by on annual cycle. In addition during the two Intensive Operating Periods (IOPs), one for 8 weeks in the spring and another for 8 weeks in the fall which capture aerosol production conditions in both the rainy and dry season, the EMSL AMS were operated in conjunction with Professors Scot Martin of Harvard and Professor Jose Jimenez of UC Boulder with special front end sampling equipment to determine not only existing SOA but the potential aerosol mass (PAM) obtained by subjecting part of the sample air to oxidizing conditions found in the rain forest atmosphere, thereby providing a good measure of the final distribution of SOA downwind from the AMS sampling site.