Size Resolved measurements of aerosol hygroscopicity and mixing state during Green Ocean Amazon (GoAmazon) 2014

Tuesday, 16 December 2014
Ryan M Thalman1, Paulo Artaxo2, Pedro Campuzano Jost3,4, Henrique M Barbosa2, Douglas A Day4,5, Suzane S de Sá6, Weiwei Hu3, Jose L Jimenez3,4, Chongai Kuang1, Brett B Palm3,4, Mira L Krüger7, Antonio O Manzi8, Scot T Martin9, Ulrich Poeschl7, Arthur J Sedlacek III1, Gunnar Senum1, Rodrigo Augusto Ferreira de Souza10, Stephen R. Springston1, M. Lizabeth Alexander11, Thomas B Watson1 and Jian Wang1, (1)Brookhaven National Laboratory, Upton, NY, United States, (2)University of Sao Paulo, Sao Paulo, Brazil, (3)University of Colorado at Boulder, Boulder, CO, United States, (4)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (5)University of Colorado at Boulder, Dept. of Chemistry and Biochemistry, Boulder, CO, United States, (6)Harvard University, School of Engineering and Applied Sciences, Cambridge, MA, United States, (7)Max Planck Institute for Chemistry, Mainz, Germany, (8)Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil, (9)Harvard University, Cambridge, MA, United States, (10)Universidade do Estado do Amazonas, Manaus, AM, Brazil, (11)Pacific Northwest National Laboratory, Environmental Molecular Sciences Laboratory, Richland, WA, United States
Measurements of size-resolved cloud condensation nucleai (CCN) spectra were performed at the T3 site of the Green Ocean Amazon (GoAmazon) field project located near Manacapuru, Brazil during 2014. The T3 site is a receptor site for both polluted urban down-wind (Manaus, BR a city of several million 70 km up wind) and background (Amazon rainforest) air-masses and can provide a contrast between clean and polluted conditions. Particle hygroscopicity (kappa) and mixing state were calculated from the particle activation spectrum measured by size selecting aerosols and exposing them to a wide range of supersaturation in the CCN counter (Droplet Measurement Technologies Continuous-Flow Streamwise Thermal Gradient CCN Chamber). The supersaturation was varied between 0.07 and 1.1% by changing a combination of both total flow rate and temperature gradient in the CCN counter. Measured spectra were examined for air masses with different level of influence from Manaus plume. Particle hygroscopicity generally peaked near noon local time which was broadly consistent with the trend in aerosol sulfate. The average kappa values during the first intensive operation period were 0.14±0.05, 0.14±0.04 and 0.16±0.06 for 75, 112 and 171 nm particles respectively. Evaluation of particle hygroscopicity and dispersion (mixing state) will be presented with respect to size and level of pollution.