HR: 09:15h
AN: B51E-04    [Abstracts]
TI: Control of SOM Stabilization by Preferential Sorption of Nitrogenous Compounds
AU: * Sollins, P
EM: phil.sollins@orst.edu
AF: Oregon State University, Forest Science Department, Corvallis, OR 97331
AU: Filley, T
EM: filley@purdue.edu
AF: Purdue University, Dept. Earth & Atmospheric Sciences, West Lafayette, IN 47907
AU: Crow, S
EM: susan.crow@orst.edu
AF: Oregon State University, Dept. Botany & Plant Pathology, Corvallis, OR 97331
AU: Swanston, C
EM: swanston1@llnl.gov
AF: Lawrence Livermore Nat. Lab., Center for Accelerator Mass Spectometry, Livermore, CA 94551
AU: Lajtha, K
EM: kate.lajtha@orst.edu
AF: Oregon State University, Dept. Botany & Plant Pathology, Corvallis, OR 97331
AU: Caldwell, B
EM: bruce.caldwell@orst.edu
AF: Oregon State University, Forest Science Department, Corvallis, OR 97331
AB: Sequential density fractionation separates organic, mineral, and organo-mineral particles mainly according to the ratio of organic to mineral material (organic loading). Previous studies all show a consistent increase in %N (decrease in C:N) with increasing particle density from about 1.6 to 2.5 g cm-3. Correlated with this increase is a decrease in polysaccharides and increase in alkyl and aromatic compounds. We interpret these trends as due to strong binding by amino-N and carboxyl-rich compounds to mineral surfaces creating a strongly sorbed N-rich inner layer onto which neutral polysaccharides and other less polar (and less strongly sorbed) compounds attach (via both electrostatic and covalent bonds) more readily than they would onto clean mineral surfaces. As a first test of this hypothesis, we fractionated a forest Andisol at 1.65, 1.8, 2.0, 2.25, and 2.6 g cm-3. Mass recovery was greatest in the 2.0-2.25 and 2.25-2.6 g cm-3 fractions. Samples were analyzed for total C and N, 13C, 15N, and 14C. Cu oxidation, TMAH, and other molecular, isotopic and spectroscopic techniques were used to determine the organic matter composition of the fractions.
DE: 1055 Organic geochemistry
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting