HR: 14:00h
AN: H23C-03    [Abstracts]
TI: From the Andes to the Atlantic: the Evolution of Organic Matter in the Amazon River System
AU: * Aufdenkampe, A K
EM: aufdenkampe@stroudcenter.org
AF: Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 United States
AU: Mayorga, E
EM: emiliom@u.washington.edu
AF: University of Washington, School of Oceanography Box 355352, Seattle, WA 98195 United States
AU: Hedges, J I
EM: jihedges@u.washington.edu
AF: University of Washington, School of Oceanography Box 355352, Seattle, WA 98195 United States
AU: McClain, M E
EM: michael.mcclain@fiu.edu
AF: Florida International University, Department of Environmental Studies 11200 SW 8th Street, Miami, FL 33199 United States
AU: Llerena, C A
EM: callerena@lamolina.edu.pe
AF: Universidad Nacional Agraria La Molina, Facultad de Ciencias Forestales Apartado Postal 456, Lima, Peru
AU: Quay, P D
EM: pdquay@washington.edu
AF: University of Washington, School of Oceanography Box 355352, Seattle, WA 98195 United States
AU: Krusche, A V
EM: alex@cena.usp.br
AF: Universidade de Sao Paulo, Centro da Energia Nuclear na Agricultura, Piracicaba, SP 13416 Brazil
AU: Richey, J E
EM: jrichey@u.washington.edu
AF: University of Washington, School of Oceanography Box 355352, Seattle, WA 98195 United States
AB: We compare the compositions of dissolved, fine and coarse particulate organic matter fractions (DOM, FPOM and CPOM respectively) from 31 river sites in Bolivia and Peru with 18 sites along the Amazon mainstem. The diversity of sites - ranging from wet and dry Andean headwater environments, to depositional foreland reaches, to major lowland rivers - allows us to assess the compositional evolution of organic matter along a 5000 km transect draining Peru and a 3000 km transect draining Bolivia. Organic matter size fractions were assessed by concentration, elemental (%OC, %N, C/N), isotopic (¹³C, ¹⁴C, ¹⁵N), lignin phenol, hydrolysable amino acid, and mineral surface area analyses. Similar to previous results from the lower Amazon and from Bolivian tributaries, the degree of mineral association was the most important factor in determining the composition of riverine organic matter. However, organic matter within a size class evolves considerably from the Andes to the lowlands. The Bolivian transect showed OM fractions becoming more diagenetically altered downstream, but the Peruvian transect showed a more complicated picture. Together, data suggest that underlying changes to sediment surface area and mineralogy may be the primary control of organic matter composition with fractions, as well as between fractions. These findings highlight the importance of organo-mineral associations and the need to describe mineral phases associated with riverine organic matter.
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1055 Organic geochemistry
DE: 1615 Biogeochemical processes (4805)
DE: 1806 Chemistry of fresh water
SC: Hydrology [H]
MN: 2005 Joint Assembly