Surface Ozone Enrichment Downwind of Manaus City, in Central Amazonia

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Luciana Varanda Rizzo, Universidade Federal de São Paulo, Departamento de Ciências Exatas e da Terra, Doadema, Brazil, Nicole P Rodrigues, Universidade Federal de São Paulo, Departamento de Ciências Exatas e da Terra, Diadema, Brazil, Joel Brito, Universidade de São Paulo, Instituto de Física, São Paulo, Brazil, Glauber G. Cirino, National Institute for Amazon Research (INPA), Manaus, Brazil, Samara Carbone, USP University of Sao Paulo, Institute of Physics, São Paulo, Brazil, Rodrigo Augusto Ferreira de Souza, Organization Not Listed, Washington, DC, United States, Henrique M Barbosa, University of Sao Paulo, Sao Paulo, United States, Paulo Artaxo, USP University of Sao Paulo, São Paulo, Brazil and Scot T Martin, Harvard University, Cambridge, MA, United States
Amazonia is a unique place to study the impact of anthropogenic emissions on atmospheric photochemistry, fueled by large inputs of solar radiation, humidity, biogenic emissions and turbulent mixing. In the wet season, thousands of km2 of Amazonian forest areas can be considered pristine, whereas in the dry season biomass burning emissions in regional scale add to picture. The Amazon region is also going through localized urban development, in particular, the Manaus city, with 2 million inhabitants. The GoAmazon2014/5 experiment seeks to understand the interactions between urban and biogenic emissions in Amazonia. The combination of biogenic volatile organic compounds and urban NOx emissions is expected to increase tropospheric O3 production, with impacts to the ecosystem and human health. To investigate this issue, surface O3 measurements were taken between Feb and Dec 2014 at two sites in Amazonia: T2, located in the outflow of the Manaus urban plume, and T3, sitting 60 km downwind of the city. The influence of the urban plume at T3 site was detected by a combination of typical ΔCN/ΔCO ratios, Hysplit backtrajectories and threshold concentrations of tracers such as particle number and black carbon. The transport from T2 to T3 typically lasted 7 hours. At T2, the O3 diurnal cycle showed a diurnal peak of 20 ppb in the wet season and of 35 ppb in the dry season, suggesting the contribution of regional biomass burning to O3 photochemical production. In the absence of urban or biomass burning emissions, O3 diurnal cycle at T3 showed a peak of 15 ppb, similar to observations taken in pristine forest areas in Amazonia. When the Manaus plume reached the T3 site in the afternoon, the diurnal O3 peak increased to 40 ppb, indicating a net O3 production rate of 3.6 ppb h-1 along this diurnal transport. When the Manaus plume reached the T3 site before sunrise, i.e., a transport during the night, the diurnal peak was anticipated and reached 25 ppb.