SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Time: 11:15:00 AM
Location: Carson B
 
CoryRM, Civil & Environmental Engineering, Michigan Technological University, Houghton, MI, USA, rmcory@mtu.edu
Green, S, A, Dept. of Chemistry, Michigan Technological University, Houghton, USA, sgreen@mtu.edu
Pregitzer, K, S, School of Forestry & Wood Products, MTU; USDA Forest Service North Central Experiment Station, Houghton, USA, kspregit@mtu.edu
 
CHEMICAL COMPOSITION OF DISSOLVED ORGANIC MATTER IN THE FORESTS OF OLYMPIC NATIONAL PARK, WA
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Despite the demonstrated importance of allochthonous dissolved organic matter (DOM) in aquatic ecosystems, it is unknown how ‘fresh’ DOM is chemically altered as it moves through the soil towards aquatic ecosystems. To understand DOM transformation as it moves with the soil water, DOM concentration, stoichiometry and light absorbing properties were investigated at two soil depths (15 and 40cm) at 11 forested study sites across Olympic National Park, WA. DOM chemical composition was measured as a function of molar ratios (N: C, H:C, O:C), average index of unsaturation, and average carbon oxidation state, all of which were obtained from CHNO elemental analysis data. The specific absorbance of DOM was calculated from dissolved organic carbon (DOC) concentrations and absorbance at 300 nm. At nearly every site, shallow soil water samples (15 cm) had lower molar ratios, higher specific absorbance, greater unsaturation and higher DOC concentrations relative to the deep soil water samples (40 cm) from the same site. The data suggest that DOM in the deeper soil water was enriched in organic-N, hydrolyzed and/or degraded into lower molecular weight material.