Comment to DOI:10.1029/2009JG001200.
Dissolved CO2 in small catchment streams of eastern Amazonia: A minor pathway of terrestrial carbon loss
Article first published online: 5 OCT 2010
Copyright 2010 by the American Geophysical Union.
Journal of Geophysical Research: Biogeosciences (2005–2012)
Volume 115, Issue G4, December 2010
How to Cite
2010), Dissolved CO2 in small catchment streams of eastern Amazonia: A minor pathway of terrestrial carbon loss, J. Geophys. Res., 115, G04005, doi:10.1029/2009JG001202., , , and (
- Issue published online: 5 OCT 2010
- Article first published online: 5 OCT 2010
- Manuscript Accepted: 18 MAY 2010
- Manuscript Revised: 12 MAY 2010
- Manuscript Received: 2 NOV 2009
- carbon dioxide;
- carbon cycle;
 Production of carbon dioxide (CO2) in soils can lead to supersaturation of dissolved free CO2 (pCO2) in groundwater, which later evades to the atmosphere as groundwater enters streams and rivers. This process could be a significant pathway for return of terrestrially fixed C to the atmosphere. We measured pCO2 monthly over two years at multiple stations along three streams from their headwaters in remnant mature forests through multiple land covers in Pará, Brazil. The pCO2 averaged 19,000 μatm in headwaters and decreased to about 4,500 μatm downstream. Similar values were measured in headwaters of two small pristine mature forest catchments. Two approaches were used to estimate groundwater pCO2 evasion: assuming that headwater pCO2 measurements reflected incoming groundwater pCO2 or that all entering stream water was in equilibrium with previously measured deep soil CO2. With these assumptions, losses from the terrestrial environment through aquatic evasion of pCO2 would be 0.02–0.15 Mg C ha−1 of land area yr−1, which is about 2–3 orders of magnitude lower than annual estimates of soil respiration and net primary productivity. However, downstream pCO2 values that appear to be in quasi-steady state indicate contributions from other C sources, such as aquatic primary production, soil erosion, dissolved organic matter, or litter inputs from streamside vegetation. Hence, lateral pCO2 loss from groundwater to streams is minor for most of the terrestrial ecosystems of this region, although C loss to streams could be significant for net terrestrial budgets in riparian ecosystems or areas experiencing erosion.