Observations of Manaus urban plume evolution and interaction with biogenic emissions in GoAmazon 2014/5
Creators: name: Cirino, Glauber
name: Brito, Joel
name: Barbosa, H. M. J.
name: Rizzo, Luciana V.
name: Tunved, Peter
name: De Sá, Suzane S.
name: Jimenez, Jose L.
name: Palm, Brett B.
name: Carbone, Samara
name: Lavric, Jost V.
name: Souza, Rodrigo A. F.
name: Wolff, Stefan
name: Walter, David
name: Tota, Júlio
name: Oliveira, Maria B. L.
name: Martin, Scot T.
name: Artaxo, Paulo
Publisher: name: Elsevier
Year: 2018
Subjects: Aerosol
GoAmazon
Manaus
Plume aging
Tropical forest
Urban pollution

description: As part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment, detailed aerosol and trace gas measurements were conducted near Manaus, a metropolis located in the central Amazon Basin. Measurements of aerosol particles and trace gases were done downwind Manaus at the sites T2 (Tiwa Hotel) and T3 (Manacapuru), at a distance of 8 and 70?km from Manaus, respectively. Based on in-plume measurements closer to Manaus (site T2), the chemical signatures of city emissions were used to improve the interpretation of pollutant levels at the T3 site. We derived chemical and physical properties for the city's atmospheric emission ensemble, taking into account only air masses impacted by the Manaus plume at both sites, during the wet and dry season Intensive Operating Periods (IOPs). At T2, average concentrations of aerosol number (CN), CO and SO2 were 5500?cm?3 (between 10 and 490?nm), 145?ppb and 0.60?ppb, respectively, with a typical ratio ?CN/?CO of 60–130 particles cm?3?ppb?1. The aerosol scattering (at RH?60%) and absorption at 637?nm?at T2 ranged from 10 to 50?M?m?1 and 5–10?M?m?1, respectively, leading to a mean single scattering albedo (SSA) of 0.70. In addition to identifying periods dominated by Manaus emissions at both T2 and T3, the plume transport between the two sampling sites was studied using back trajectory calculations. Results show that the presence of the Manaus plume at site T3 was important mainly during the daytime and at the end of the afternoons. During time periods directly impacted by Manaus emissions, an average aerosol number concentration of 3200?cm?3 was measured at T3. Analysis of plume evolution between T2 and T3 indicates a transport time of 4–5?h. Changes of submicron organic and sulfate aerosols ratios relative to CO (?OA/?CO and ?SO4/?CO, respectively) indicate significant production of secondary organic aerosol (SOA), corresponding to a 40% mass increase in OA and a 30% in SO4 mass concentration. Similarly, during air mass arrival at T3 the SSA increased to 0.83 from 0.70?at T2, mainly associated with an increase in organic aerosol concentration. Aerosol particle size distributions show a strong decrease in the Aitken nuclei mode (10–100?nm) during the transport from T2 to T3, in particular above 30?nm, as a result of efficient coagulation processes into larger particles. A decrease of 30% in the particle number concentration and an increase of about 50?nm in geometric mean diameter were observed from T2 to T3 sites. The study of the evolution of aerosol properties downwind of the city of Manaus improves our understanding of how coupling of anthropogenic and biogenic sources may be impacting the sensitive Amazonian atmosphere.