author = "Shilling, John E. and Pekour, Mikhail S. and Fortner, Edward C. 
                         and Artaxo, Paulo and S{\'a}, Suzane de and Hubbe, John M. and 
                         Longo, Karla Maria and Machado, Luiz Augusto Toledo and Martin, 
                         Scot T. and Springston, Stephen R. and Tomlinson, Jason and Wang, 
          affiliation = "{Pacific Northwest National Laboratory} and {Pacific Northwest 
                         National Laboratory} and Center for Aerosol and Cloud Chemistry, 
                         Aerodyne Research and {Universidade de S{\~a}o Paulo (USP)} and 
                         {Harvard University} and {Pacific Northwest National Laboratory} 
                         and {University Space Research Association} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Harvard University} 
                         and {Brookhaven National Laboratory} and {Pacific Northwest 
                         National Laboratory} and {Brookhaven National Laboratory}",
                title = "Aircraft observations of the chemical composition and aging of 
                         aerosol in the Manaus urban plume during GoAmazon 2014/5",
              journal = "Atmospheric Chemistry and Physics",
                 year = "2018",
               volume = "18",
               number = "14",
                pages = "10773--10797",
                month = "July",
             abstract = "The Green Ocean Amazon (GoAmazon 2014/5) campaign, conducted from 
                         January 2014 to December 2015 in the vicinity of Manaus, Brazil, 
                         was designed to study the aerosol life cycle and aerosol-cloud 
                         interactions in both pristine and anthropogenically influenced 
                         conditions. As part of this campaign, the U.S. Department of 
                         Energy (DOE) Gulfstream 1 (G-1) research aircraft was deployed 
                         from 17 February to 25 March 2014 (wet season) and 6 September to 
                         5 October 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 and secondary organic aerosol (SOA) formation and 
                         aging. In the first portion of the paper, we provide an overview 
                         of the data and compare and contrast the data from the wet and dry 
                         season. Organic aerosol (OA) dominates the deploymentaveraged 
                         chemical composition, comprising 80%of the nonrefractory PM1 
                         aerosol mass, with sulfate comprising 14 %, nitrate 2 %, and 
                         ammonium 4 %. 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 OA mass in the dry, 
                         but not wet, season. However, the OA was more oxidized in the dry 
                         season, with the median of the mean carbon oxidation state 
                         increasing from -0:45 in the wet season to -0:02 in the dry 
                         season. In the second portion of the paper, we discuss the 
                         evolution of the Manaus plume, focusing on 13 March 2014, one of 
                         the exemplary days in the wet season. On this flight, we observe a 
                         clear increase in OA concentrations in the Manaus plume relative 
                         to the background. As the plume is transported downwind and ages, 
                         we observe dynamic changes in the OA. The mean carbon oxidation 
                         state of the OA increases from -0:6 to -0:45 during the 4-5 h of 
                         photochemical aging. Hydrocarbon-like organic aerosol (HOA) mass 
                         is lost, with \ΔHOA/\ΔCO values decreasing from 17.6 
                         \μgm-3 ppmv-1 over Manaus to 10.6 \μgm-3 ppmv-1 95 km 
                         downwind. Loss of HOA is balanced out by formation of oxygenated 
                         organic aerosol (OOA), with \ΔOOA/\ΔCO increasing from 
                         9.2 to 23.1 \μgm-3 ppmv-1. Because hydrocarbon-like organic 
                         aerosol (HOA) loss is balanced by OOA formation, we observe little 
                         change in the net \Δorg/\ΔCO values; 
                         \Δorg/\ΔCO averages 31 \μgm-3 ppmv-1 and does 
                         not increase with aging. Analysis of the Manaus plume evolution 
                         using data from two additional flights in the wet season showed 
                         similar trends in \Δorg/\ΔCO to the 13 March flight; 
                         \Δorg/\ΔCO values averaged 34 \μgm-3 ppmv-1 and 
                         showed little change over 4-6.5 h of aging. Our observation of 
                         constant \Δorg/\ΔCO are in contrast to literature 
                         studies of the outflow of several North American cities, which 
                         report significant increases in \Δorg/\ΔCO for the 
                         first day of plume aging. These observations suggest that SOA 
                         formation in the Manaus plume occurs, at least in part, by a 
                         different mechanism than observed in urban outflow plumes in most 
                         other literature studies. Constant \Δorg/\ΔCO with 
                         plume aging has been observed in many biomass burning plumes, but 
                         we are unaware of reports of fresh urban emissions aging in this 
                         manner. These observations show that urban pollution emitted from 
                         Manaus in the wet season forms less particulate downwind as it 
                         ages than urban pollution emitted from North American cities.",
                  doi = "10.5194/acp-18-10773-2018",
                  url = "http://dx.doi.org/10.5194/acp-18-10773-2018",
                 issn = "1680-7316 and 1680-7324",
             language = "en",
           targetfile = "shilling_aircraft.pdf",
        urlaccessdate = "25 jul. 2021"