Dissolved organic material (DOM) is a major pool of organic carbon in all aquatic ecosystems and has high concentrations in soil interstitial water. DOM represents both a substrate for microbial growth and an important characteristic of aquatic and soil environments, regulating light penetration in lakes and streams and the bioavailability of trace metals and organic contaminants, for example. Diverse studies have shown that the concentration and chemical properties of DOM reflects the predominant DOM sources. In lakes and streams, DOM can originate from the surrounding watershed (allochthonous sources) and from production and decomposition of DOM within the aquatic ecosystem (authochthonous sources). The understanding within the LTER network of the dynamic processes controlling DOM fluxes and reactivity in ecosystems can be advanced by increasing the application of modern spectroscopic methods for chemical characterization of DOM in monitoring programs and short term research projects. An analysis of DOM from many LTER sites conducted as part of a 2004 LTER workshop on the biogeochemistry of DOM showed that spectroscopic methods can be used to reveal the broad range in DOM quality that occurs both across the LTER network and among ecosystems within a given LTER site (Jaffe R, McKnight D, Maie N, Cory, R., McDowell, W. H., Campbell, J. L. 2008. Spatial and temporal variations in DOM composition in ecosystems: The importance of long-term monitoring of optical properties. Journal of Geophysical Research-Biogeosciences 113 G4 G04032). The use of fluorescence spectroscopy to understand DOM biogeochemistry has expanded since then and has the potential to be incorporated into monitoring programs. The working group session will begin with an overview presentation on DOM quality variations in the LTER network and continue with presentations and discussion of analytical approaches for characterization of DOM in monitoring programs to understand changes in carbon cycling and biogeochemsitry. The participants will develop overarching hypotheses and recommendations for DOM research in the LTER network.

In addition to a working group session during the ASM, the DOM Characterization Working Group led by Rudolf Jaffe and Diane McKnight will hold a 2-day post-conference training workshop on fluorescence methods for characterization of dissolved organic material in surface waters and soil interstitial waters. The workshop will be held at INSTAAR at the University of Colorado on Thursday and Friday (September 17-18), and will include training in spectroscopic methods and data analysis using PARAFAC (parallel factor analysis). Participants (up to 15) should bring a laptop with MATLAB installed. Participants may bring a small number of samples(3-4) for analysis during the workshop. Please contact Kaelin Cawley (kaelin.cawley@colorado.edu) for more information. Some housing will be available in Boulder.