Modeling the Chemical Interaction between Manaus Emissions and the Amazon Rainforest Plume with GECKO-A: A Detailed Look at Secondary Organic Carbon Composition

Description

The GOAmazon field campaign focused on the interplay between biogenic air masses and anthropogenic emissions in the area of Manaus (Brazil). This location is unique because it is an important urban area situated in the middle of a vast expanse of Amazon rainforest. The DOE/ASR dataset gathered from the GOAmazon field campaign has been used here to evaluate the ability of the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to reproduce the observed trace gas concentrations and aerosol composition. GECKO-A is a tool designed to systematically generate hyper-explicit chemical schemes describing the atmospheric oxidation of hydrocarbons, from the emission to the total transformation to CO2. Emissions from the Amazon rainforest and Manaus were estimated from existing inventories. The full oxidation mechanism of 47 anthropogenic and 7 biogenic primary hydrocarbons was generated with GECKO-A and implemented in a box model representing the advection of an air parcel over the rainforest. The simulated air parcel was made to intercept Manaus urban emissions at different times of the day. The GOAmazon dataset was used to validate emissions, oxidants levels and secondary organic carbon. The explicit simulations have been used to explore the speciation of gaseous and particulate organic matter aerosol composition. First results show that Manaus emissions have very little impact on organic carbon speciation and concentrations, with no lasting effect downwind of Manaus. A first explanation would suggest that the rainforest emissions overwhelm the urban local emissions. Different tests were performed to look at the sensitivities of this system, especially regarding the magnitude of urban emissions and the residence time over the city.