Organic Carbon Export From a Mixed Land Use Watershed

Changes in land cover and land use for the purpose of agricultural production have long been implicated as significant contributors of nonpoint source pollution and subsequent local and regional water quality problems. In addition to changes in sediment and nutrient export from disturbed ecosystems, carbon export can also be influenced by such changes in land use and land cover. In order to gain insight into the influence of land use on organic carbon export we have initiated a molecular and stable carbon isotope study of dissolved, colloidal and particulate organic matter collected monthly and during storm events from locations in Big Pine Creek watershed, a mixed land use watershed located in West-Central Indiana. Water samples were separated into coarse particulate organic matter, colloidal organic matter, and dissolved organic matter with glass fiber filters and cross flow ultrafiltration. The organic matter from these samples is being characterized by molecular and stable isotope techniques to determine regional source by the use diagnostic lignin monomer distributions extracted via alkaline cupric oxide oxidation and tetramethylammonium hydroxide thermochemolysis. Ongoing analysis will investigate how differences in land use and/or land management practices may influence the extent and nature of carbon export from terrestrial systems.