Gas- and particle-phase chemical composition measurements onboard the G-1 research aircraft during the GoAmazon campaign

 
Poster PDF

Authors

John E Shilling — Pacific Northwest National Laboratory
Mikhail S. Pekour — Pacific Northwest National Laboratory
Ed Fortner — Aerodyne Research, Inc.
Paulo Artaxo — University of Sao Paulo
John Hubbe — Pacific Northwest National Laboratory
Karla Longo — National Institute for Space Research (INPE)
Luiz Augusto Toledo Machado — INPE-CPTEC
Scot T. Martin — Harvard University
Fan Mei — Pacific Northwest National Laboratory
Stephen R. Springston — Brookhaven National Laboratory
Jason Tomlinson — Pacific Northwest National Laboratory
Jian Wang — Washington University in St. Louis

Category

GoAmazon – Clouds and aerosols in Amazonia

Description

The Green Ocean Amazon (GoAmazon) campaign conducted from January 2014 – December 2015 in the vicinity of Manaus, Brazil, was designed to study the aerosol lifecycle and aerosol-cloud interactions in both pristine and anthropogenically influenced conditions. As part of this campaign, the DOE G-1 research aircraft was deployed from February 17th – March 25th 2014 (wet season) and September 6th – October 5th 2014 (dry season) to investigate aerosol and cloud properties aloft. Here, we present results from the G-1 deployments focusing on measurements of the aerosol chemical composition, aerosol sources, and SOA formation. Organics dominate the deployment-averaged chemical composition, comprising 78 % of the total mass with sulfate 12%, nitrate 5%, and ammonium 4%. Surprisingly, this product distribution was unchanged between seasons, despite the fact that total aerosol loading was significantly higher in the dry season and that regional and local biomass burning was a significant source of organic aerosol mass in the dry, but not wet, season. We also find unexpected results when examining the evolution of the Manaus plume on March 13th, 2014, one of the campaign golden days in the wet season. On this flight, we observe clear enhancements of SOA concentrations inside the Manaus plume and modest enhancements in the organic aerosol mean carbon oxidation state as the plume ages. However, at the same time, we do not observe a change in the ratio of excess OA to excess CO (ΔOA/ ΔCO) with aging, in contrast to many studies that find this quantity increases with aging. These seemingly contradictory observations suggest that SOA formation in the Manaus plume occurs, at least in part, by a different mechanism than observed in urban outflow plumes of several North American cities.