News & Events

Grad student talk - Dissolved organic matter cycling in the Boulder Creek watershed

Thursday, March 11, 2010, 4:30PM - 5:30PM


Rachel Gabor



RL-1 269

As part of the Boulder Creek Critical Zone Observatory, water samples were collected from several sites along Boulder Creek at regular time intervals beginning in May 2008. The concentration and quality of the Dissolved Organic Matter (DOM) in these samples was analyzed to understand the response to seasonal changes and variations in flow rates. Filtered samples were fractionated using XAD-8 resin and both whole water and fulvic acid fractions were analyzed for dissolved organic carbon concentration as well as with fluorescence and UV-VIS spectroscopy to determine its chemical character. In addition to stream measurements, surface soil samples along several transects were collected from Gordon Gulch as well as deeper samples from soil pits on both north-facing and south-facing slopes . DOM from these samples was leached with potassium sulfate and analyzed using the same techniques as the stream samples to compare the characteristics of the terrestrial organic matter available to be leached from the watershed with that of the DOM in the stream. While available soluble organic matter was significantly higher at the surface and tended to steadily decrease with depth, amount and chemical character did vary with soil horizon. These results were compared to the chemical signature of the DOM from the stream the catchment feeds. Organic matter from the surface was much more similar to the stream DOM than matter near bedrock