DAVIDSON, E. A.

FIGUEIREDO, R. O.

MARKEWITZ, D.

SILVA, P. S.

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Fechar JanelaID do Resumo: 525Dissolved CO2 in Small Catchment Streams of Eastern AmazoniaEric A. Davidson, The Woods Hole Research Center, edavidson@whrc.org(Apresentador) Ricardo O. Figueiredo, Embrapa, ricfig@uga.edu Daniel Markewitz, University of Georgia, dmarke@warnell.uga.edu Patricio S Silva, Universidade do Estado do Pará, patricioengamb@gmail.com Production of carbon dioxide (CO2) in soils can lead to supersaturation of dissolvedCO2 (pCO2) in groundwater. As groundwater enters streams and rivers, the pCO2may evade to the atmosphere, thus transferring C that was fixed in terrestrialecosystems to the atmosphere via an aquatic pathway. It has been postulated that thisprocess could be a significant pathway for return of terrestrially fixed C to theatmosphere in the Amazon Basin. We conducted a study of pCO2 along threestreams from their headwaters in remnant mature forests, through pastures, secondaryforests, and agriculture in the municipality of Paragominas, Pará. The watershedareas ranged from 3000 to 16000 ha, and the mean downstream discharge rangedfrom 0.3 to 2.9 m3/s. Concentrations of pCO2 were measured monthly at 3-7 stationsalong each stream for a two-year period. The measured pCO2 averaged about 600uM in headwaters and decreased to about 100 uM downstream. For an upper limitestimate of CO2 loss by this pathway, we assume that all of the water entering thestream had the same pCO2 as was measured in the headwaters, and that all of thepCO2 eventually was evaded to the atmospheric. With these assumptions, the amountof C lost from the terrestrial environment through aquatic evasion of pCO2 would be onthe order of 20-40 kgC per hectare of land area per year, which is about 3 orders ofmagnitude lower than annual estimates of soil CO2 efflux. Hence, while thegroundwater may be supersaturated in pCO2, this is a trivial pathway of carbon fluxfrom the terrestrial ecosystem in these small watersheds. Large reported fluxes ofCO2 evading to the atmosphere from Amazonian rivers likely representsdecomposition of organic matter entering the river either from aquatic primaryproduction or as detritus associated with eroded soils and litter inputs fromstreamside vegetation.Sessão:  Biogeoquímica - A biogeoquímica das interações entre terra e água:integrando pequenos reservatórios a grande bacia.Tipo de Apresentação:   OralFechar Janelaconverted by Web2PDFConvert.com

Dissolved CO2 in small catchment streams of Eastern Amazonia.

http://www.alice.cnptia.embrapa.br/alice/bitstream/doc/410187/1/ID40910.pdf

Dissolved CO2 in small catchment streams of Eastern Amazonia.

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