HR: 1330h
AN: B32A-0372    [PDF]
TI: The Role of Sorption in Retention of Dissolved Organic Carbon in Soils Typical of the Lowland Amazon Basin
AU: * Remington, S M
EM: sunny9@u.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AU: Neu, V
EM: bioneu@inpa.gov.br
AF: CENA - Universidade de Sao Paulo, Av. Centenario, 303, Piracicaba, SP 13400-970 Brazil
AU: Richey, J
EM: jrichey@u.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AB: The overall question we are addressing is: What role does the evasion (out gassing) of CO$_{2}$ from the river system to the atmosphere play in the carbon cycle of moist tropical forests? Recent evidence suggests that the Amazon may be a net sink of atmospheric CO$_{2}$ of 1-9 Mg C ha$^{-1}$ y$^{-1}$. We have made recent calculations that suggest that the evasion of CO$_{2}$ from the river system of the central Amazon basin is on the order of 1.2 $\pm$ 0.3 Mg C ha$^{-1}$ y$^{-1}$. A flux of this magnitude suggests that the ecosystem processes involved in river corridors represent a significant pathway for the export of carbon fixed on land in the humid tropics at a globally significant level. The quantity of dissolved CO$_{2}$ (pCO$_{2}$) in surface waters of tropical river systems is the product of a long sequence of complex biological, hydrological and geochemical processes. Sorption is an important geochemical process that removes dissolved organic carbon (DOC) from water percolating through soils, which may eventually flow into the river channel (via groundwater and subsurface flow) where it may be respired to CO$_{2}$. Soil properties, such as texture, Fe- and Al-oxide content, mineral surface area and soil organic carbon content, are known to affect the concentration of DOC in soil pore water and, therefore, the quantity of DOC transported to river channels. These soil properties vary with soil type. We collected samples from two depths of three different soil types typically found in the lowland Amazon basin for use in equilibrium and kinetic laboratory "batch" experiments, and for analysis of soil properties. We examined relationships between sorption and soil properties in an attempt to estimate the quantity of DOC sorbed based on soil type. Finally, we compared the results of the laboratory experiments to field data. Explaining and quantifying DOC lost to sorption as a function of soil properties is an important step in understanding the export of carbon fixed on land and transported to rivers.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting