Biomass burning emission disturbances of isoprene oxidation in a tropical forest

摘要: Abstract. We present a characterization of the chemical composition atmosphere of Brazilian Amazon rainforest based on trace gas measurements carried out during South AMerican Biomass Burning Analysis (SAMBBA) airborne experiment in September 2012. analyzed observations primary biomass burning emission tracers, i.e., carbon monoxide (CO), nitrogen oxides ( NOx ), ozone ( O3 isoprene, and its main oxidation products, methyl vinyl ketone (MVK), methacrolein (MACR), isoprene hydroxy hydroperoxide (ISOPOOH). The focus SAMBBA was primarily emissions, but there were also several flights in areas Amazon forest not directly affected by biomass burning, revealing background with a signature burning due to long-range transport tracers from both Africa eastern part of Amazonia. used [MVK  +  MACR   ISOPOOH]  ∕  [isoprene] ratio and hydroxyl radical (OH) indirect calculation assess oxidative capacity forest atmosphere. compared regions (CO < 150 ppbv), fresh aged smoke plumes classified according to their photochemical age ([ ]   [CO]), evaluate impact of emissions oxidative capacity forest atmosphere. observed that disturb isoprene oxidation reactions, especially for plumes ([MVK   [isoprene]  =   7) downwind. The oxidation isoprene is higher at lower altitudes ( ∼  500 m) than plumes, anticipating near surface a complex chain oxidation reactions which may be related secondary organic aerosol (SOA) formation. We proposed refinement OH the sequential reaction model, considers vertical horizontal transport for regimes environment. Our approach for the [OH] estimation resulted values same order magnitude a recent observation [OH]  ≅  10 6 (molecules cm −3 ). During plume regime, profile of ratio showed evidence an increase oxidizing power transition from planetary boundary layer cloud (1000–1500 m). These high of [OH] (1.5  ×  molecules cm ) and [MVK  (7.5) indicate significant change above inside decks edge effects on photolysis rates, have major impact production rates.