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@Article{MorganABDFLLJHLAC:2020:TrAgBi,
               author = "Morgan, William T. and Allan, James D. and Bauguitte, 
                         St{\'e}phane and Darbyshire, Eoghan and Flynn, Michael J. and 
                         Lee, James and Liu, Dantong and Johnson, Ben and Haywood, Jim and 
                         Longo, Karla Maria and Artaxo, Paulo E. and Coe, Hugh",
          affiliation = "{University of Manchester} and {University of Manchester} and 
                         {Cranfield University} and {University of Manchester} and 
                         {University of Manchester} and {University of York} and 
                         {University of Manchester} and {Met Office} and {Met Office} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universidade de S{\~a}o Paulo (USP)} and {University of 
                         Manchester}",
                title = "Transformation and ageing of biomass burning carbonaceous aerosol 
                         over tropical South America from aircraft in situ measurements 
                         during SAMBBA",
              journal = "Atmospheric Chemistry and Physics",
                 year = "2020",
               volume = "20",
               number = "9",
                pages = "5309--5326",
                month = "May",
             abstract = "We present a range of airborne in situ observations of biomass 
                         burning carbonaceous aerosol over tropical South America, 
                         including a case study of a large tropical forest wildfire and a 
                         series of regional survey flights across the Brazilian Amazon and 
                         Cerrado. The study forms part of the South American Biomass 
                         Burning Analysis (SAMBBA) project, which was conducted during 
                         September and October 2012. We find limited evidence for net 
                         increases in aerosol mass through atmospheric ageing combined with 
                         substantial changes in the chemical properties of organic aerosol 
                         (OA). Oxidation of the OA increases significantly and rapidly on 
                         the scale of 2.5-3 h based on our case study analysis and is 
                         consistent with secondary organic aerosol production. The 
                         observations of limited net enhancement in OA coupled with such 
                         changes in chemical composition imply that evaporation of OA is 
                         also occurring to balance these changes. We observe significant 
                         coatings on black carbon particles at source, but with limited 
                         changes with ageing in both particle core size and coating 
                         thickness. We quantify variability in the ratio of OA to carbon 
                         monoxide across our study as a key parameter representing both 
                         initial fire conditions and an indicator of net aerosol production 
                         with atmospheric ageing. We observe ratios of 0.075-0.13 mu g 
                         sm(-3) ppbv(-1) in the west of our study region over the Amazon 
                         tropical forest in air masses less influenced by precipitation and 
                         a value of 0.095 mu g sm(-3) ppbv(-1) over the Cerrado environment 
                         in the east (where sm(-3) refers to standard metre cubed). Such 
                         values are consistent with emission factors used by numerical 
                         models to represent biomass burning OA emissions. Black carbon 
                         particle core sizes typically range from mean mass diameters of 
                         250 to 290 nm, while coating thicknesses range from 40 to 110 nm 
                         in air masses less influenced by precipitation. The primary driver 
                         of the variability we observe appears to be related to changes at 
                         the initial fire source. A key lesson from our study is that 
                         simply aggregating our observations as a function of atmospheric 
                         ageing would have been misleading due to the complex nature of the 
                         regional aerosol and its drivers, due to the many conflating and 
                         competing factors that are present. Our study explores and 
                         quantifies key uncertainties in the evolution of biomass burning 
                         aerosol at both near-field and regional scales. Our results 
                         suggest that the initial conditions of the fire are the primary 
                         driver of carbonaceous aerosol physical and chemical properties 
                         over tropical South America, aside from significant oxidation of 
                         OA during atmospheric ageing. Such findings imply that 
                         uncertainties in the magnitude of the aerosol burden and its 
                         impact on weather, climate, health and natural ecosystems most 
                         likely lie in quantifying emission sources, alongside atmospheric 
                         dispersion, transport and removal rather than chemical 
                         enhancements in mass.",
                  doi = "10.5194/acp-20-5309-2020",
                  url = "http://dx.doi.org/10.5194/acp-20-5309-2020",
                 issn = "1680-7316 and 1680-7324",
             language = "en",
           targetfile = "morgan_transformation.pdf",
        urlaccessdate = "13 abr. 2021"
}


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