SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Time: 3:00:00 PM
Location: Carson B
 
WaiserMJ, National Water Research Institute, Saskatoon, Canada, marley.waiser@ec.gc.ca
Robarts, R, D, National Water Research Institute, Saskatoon, Canada, richard.robarts@ec.gc.ca
 
CONCENTRATION AND CHARACTER OF DISSOLVED ORGANIC CARBON IN TWO HYDROLOGICALLY DISTINCT PRAIRIE WETLANDS.
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Wetlands are key ecological components of the North American prairies. Results of studies conducted on two hydrologically distinct wetlands at the St. Denis National Wildlife Area near Saskatoon, SK. indicate strong linkages between DOC concentration, climate and pond hydrology. DOC evapoconcentrates in ponds that lose most of their water by evaporation. Consequently, a strong correlation between DOC concentration and the biologically conservative chloride ion (r2=0.86) exists. In ponds losing most of their water via infiltration to the pond margin, seasonal DOC concentrations remain constant. In the pond where evaporation was dominant, seasonal changes in DOC molecular weight (elucidated from tangential filtration, absorbance ratios and mass electrospray mass spectrometry), aromaticity (from 13C NMR analyses), del 13C ratios, absorptivity coefficients and spectral slopes are linked to photodegradative processes. Photodegradation is strong in alkaline, well-mixed ponds with little surrounding vegetation but less effective in well-shaded infiltration ponds.