A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Abstract submitted for presentation at the2 nd International LBA Scientific Conference, Manaus, Brazil, July 7-10, 2002Continuous Measurements of Fluxes of Biogenic VOCsin the Amazon BasinL.V. Gatti 1 , C. R. Trostdorf 1 , A. M. Cordova 1 , A. Yamazaki 1 , C.A.B.Aquino 2 , N.Bonelli 2 , W. C. Martins 3 , A. Guenther 41 Instituto de Pesquisas Energéticas e Nucleares (IPEN), Travessa R, 400, Cidade Universitária,São Paulo, Brazil, CEP: 05508-900 e-mail: lvgatti@net.ipen.br2 ULBRA Instituto Luterano de Ensino Superior de Ji-Parana, Brazil3 Universidade Federal do Para, Santarem, Brazil4 NCAR – Atmospheric Chemistry Division, Boulder, CO, USAIt is well recognized that the tropical forests are an important global sourceof VOC (volatile organic compounds), as well as a number of other atmospherictrace gases. The high biodiversity in tropical rainforests complicates theextrapolation of biogenic volatile organic compound (BVOC) emissions from leaflevelmeasurements to landscape and regional or global scales. In Amazonia, asignificant fraction of the carbon emitted from the biosphere to the atmosphere isemitted in the form of VOCs, and the knowledge of these fluxes is important toour understanding of the tropical and global atmospheric chemistry and carboncycling.As part of the LBA (The Large Scale Biosphere-Atmosphere Experiment inAmazonian) experiment, continuous VOCs gradient measurements are beingperformed in four sites in Amazonia. The first two sites are located at theNational Forest of Tapajós, Pará State, Santarém, Km 67 of BR 163, one at aprimary forest. The preliminary average flux results is about 4 mg m-2 h-1(average concentration ~ 5 ppb) and another at a forest were selective logging istaking place, Km 83 of BR 163, were the preliminary average flux of about 2 mgm-2 h-1 (average concentration ~ 3.5 ppb). The measurements were made at 65and 55 m heights simultaneity in an LBA Tower (20 and 10 meters above forestcanopy, respectively). The other two sites are located in the Rondonia state, at aprimary forest and also at a pasture site. The forest site is the Biological Reserveof Jaru, Primary forest, with the gradient measurements taking place at 65 and55 m above the ground (30 and 20 m above forest canopy, respectively, average~7 ppb). In the pasture site (grass vegetation), the gradient measurements aretaking place at 8 and 3 m above the ground (~1.7 ppb). The gradientconcentration measurements are being used to calculate VOC fluxes. Theexpected seasonality of VOC fluxes and emissions are being captured. Thepreliminary results indicates that the forest respond with less isoprene fluxes inperturbed forest.Financing by MCT, CNPq and FAPESP