Trace Gases Concentrations during Dry and Wet Seasons in the Amazon Basin
Luciana
Vanni
Gatti, IPEN - Laboratorio de Quimica Atmosferica, lvgatti@net.ipen.br
(Presenting)
Ana Maria
Leal
Cordova, IPEN - Laboratorio de Quimica Atmosferica, acordova@intihuasi.inia.cl
Amelia
Yamazaki, IPEN - Laboratorio de Quimica Atmosferica, amelia@net.ipen.br
Angelica
Pretto, IPEN - Laboratorio de Quimica Atmosferica, apretto@net.ipen.br
James
William
Munger, Harvard University, Division of Engineering and Applied Sciences, jwm@io.harvard.edu
Paulo
Artaxo, Instituto de Fisica da USP, artaxo@if.usp.br
Carlos
Augusto Bauer
Aquino, Univ. Luterana do Brasil - Ji-Paraná (ULBRA), paquino@brturbo.com
Lizia
Murbach, Univ. Luterana do Brasil - Ji-Paraná (ULBRA), lizia19@ig.com.br
Williams
Castro
Martins, UFPA - Santarem, williamsmartins@hotmail.com
Meinrat
O.
Andreae, Max Planck Institute for Chemistry, Biogeochemistry Dept, andreae@mpch-mainz.mpg.de
Franz
Meixner, Max Planck Institute for Chemistry, Biogeochemistry Dept, meixner@mpch-mainz.mpg.de
Duli
Chand, Max Planck Institute for Chemistry, Biogeochemistry Dept, duli@mpch-mainz.mpg.de
Ivonne
Trebs, Max Planck Institute for Chemistry, Biogeochemistry Dept, ivonne@mpch-mainz.mpg.de
Several intensive experiments were performed from 1999 to 2002 in different regions of Amazonia, such as Ouro Preto do Oeste (pasture site - Rondonia), Balbina (forest site at 180 km north of Manaus), and Floresta Nacional (FLONA) do Tapajós (Pará).
During the wet season in Amazônia, the ozone concentration at mid-day (solar radiation maximum) is very similar for the 3 sites studied. The average ozone concentration is between 12 – 14 ppb. At nighttime, we observed significant differences in ozone concentrations for the different sites. At the FLONA Tapajós, the nighttime concentration is similar to diurnal values, with a very high 9 to 11 ppb average. The high ozone concentration during nighttime can be explained by vertical transport of ozone rich air masses, which occurs frequently during the wet season. With higher O3, the soil NO will have a shorter lifetime and more of it may be converted to NO2 and recycled in the canopy instead of escaping to the free atmosphere.
During the dry season, typical daytime ozone concentrations were 25-50 ppb, depending on the concentration of biomass burning trace gas precursors. At nighttime, the ozone average concentration was similar for the several sites, at around 12 ppb. Rondônia is the site with the highest observed ozone concentration. here, the average was 50 ppb, compared to 25 ppb at the FLONA Tapajós where the biomass burning impact is lower.
Similarly to O3, the NOx concentrations differ significantly between wet and dry seasons, due to high biomass burning emissions. The average concentration for the wet season for NO was 0.23 ppb and NO2 was 0.69 ppb, while for the dry season NO averaged at a low 0.04 ppb and NO2 at 2.73 ppb.
Typical levels of CO in the Amazon basin during the wet season were 100 - 150 ppb. In Rondonia, the highest values were observed because of the strong anthropogenic impact on this region, while at FLONA Tapajós the CO average concentration was less than 100 ppb. During the dry season in Rondônia, the observed nighttime average was around 1000-1200 ppb, while during daytime we observed an average of 600 ppb. At FLONA Tapajós, during the nighttime CO was measured at 500 ppb during the peak of the burning season (Oct-Dec) and 200 ppb during the dry season, in the absence of significant biomass burning. At the FLONA Tapajós, a typical daytime average was around 200 ppb, with values similar for both dry and wet seasons.
Research project financed by CNPq and FAPESP.