Biomass burning and natural emissions in the brazilian Amazon rainforest: impact on the oxidative capacity of the atmosphere

• Ano de defesa: 2017
• Autor(a) principal: Fernando Cavalcante dos Santos
• Orientador(a): Karla Maria Longo de Freitas, Alex Guenther
• Banca de defesa: Jose Oscar Willian Vega Bustillos, Demerval Soares Moreira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Instituto Nacional de Pesquisas Espaciais (INPE)
• Programa de Pós-Graduação: Programa de Pós-Graduação do INPE em Ciência do Sistema Terrestre
• País: BR
• Link de acesso: http://urlib.net/sid.inpe.br/mtc-m21b/2017/05.29.14.21

Emitted by vegetation, isoprene (2-methyl-1,3-butadiene) is the most abundant non-methane hydrocarbons, with an annual global emission calculated ranging from 440 to 660Tg carbon, depending on the driving variables like temperature, solar radiation, leaf area index and plant functional type. It is estimated, for example, that the natural compounds like isoprene and terpenes present in the troposphere are about 90\% and 50\%, respectively, removed from the atmosphere by oxidation performed by hydroxyl radical (OH). Furthermore, the oxidation products of isoprene may contribute to secondary organic aerosol (SOA) formation, affecting the climate and altering the properties and lifetimes of clouds. Considering the importance of these emissions and the hydroxyl radical reaction in the atmosphere, the SAMBBA (South American Biomass Burning Analysis) experiment, which occurred during the dry season (September 2012) in the Amazon Rainforest, provided information about the chemical composition of the atmosphere through airborne observations. Although primarily focused on biomass burning flights, the SAMBBA project carried out other flights providing indirect oxidative capacity data in different environments: natural emission dominated flights and biomass-burning flights with fresh plumes and aged plumes. In this study, we evaluate the oxidative capacity of the Amazon rainforest in different environments, both for the unpolluted and biomass-burning disturbed atmosphere using the ratio [MVK + MACR]/[Isoprene]. Beyond that, we propose an improvement on the formulation of indirect OH density calculation, using the photochemical aging [O$_{3}$]/[CO] as a parameter. Using a synergistic approach, balancing numerical modeling and direct observations, the numerical model BRAMS was coupled to MEGAN emission model to get a better result for isoprene and OH in the atmosphere, representing the observations during SAMBBA field campaign. In relation to OH estimation, we observed an improvement in the concentration values using the modified sequential reaction model, for both biomass burning regimes and background environment. We also detected a long-range transport events of O$_{3}$ during SAMBBA experiment, considering the high levels of O3 in aged plumes at high altitudes (5,500 6,500 m), and the detection of an O$_{3}$ inflow in the Amazon basin from Africa. These findings support the importance of long-range transport events as a source of O$_{3}$ into the troposphere in the Amazon basin, which could even alter the atmospheric composition within the planetary boundary layer and alter the oxidative capacity in the region. The model results showed a reasonable agreement for isoprene concentration, although more investigation needed for the OH simulation.