Water Resources Research Act Program

Details for Project ID 2007MT147B

Identifying and characterizing sources of dissolved organic carbon in the Big Hole and Clark Fork Rivers, a continued investigation

Institute: Montana
Year Established: 2007 Start Date: 2007-03-01 End Date: 2008-02-28
Total Federal Funds: $8,586 Total Non-Federal Funds: $17,177

Principal Investigators: Stephen Parker, Douglas Cameron

Project Summary: Recent work has identified daily concentration cycles in dissolved organic (DOC) and inorganic carbon (DIC) in the Clark Fork (CFR) and Big Hole (BHR) Rivers in Montana . The DOC in the two rivers showed inverse temporal patterns suggesting that very different mechanisms control the processes in these two rivers. Preliminary study using an isolation chamber on the BHR suggested that the large nighttime increase in DOC observed may have been due to groundwater influx through benthic sediments associated with the daily evapotranspiration cycle. The stable C-isotope composition of the DIC was also investigated. The 3C-DIC in both the CFR and BHR showed the patterns expected for DIC that is influenced primarily by photosynthesis and respiration. This proposal outlines work to further test the reproducibility of the observed diel cycles in DIC and DOC. Also, the work described will help define the sources and causes of these daily DOC changes using additional laboratory and field experiments. Furthermore, the project will attempt to identify the types and molecular-weight distributions of organic compounds that make-up the DOC using Liquid Chromatography-Mass Spectrometry (LC-MS) analysis.