SURVEYING THE REACTIVITY OF DISSOLVED ORGANIC CARBON WITHIN THE STREAM-GROUNDWATER INTERFACE OF THE KALAMAZOO RIVER, ALBION, MI

Dissolved Organic Carbon (DOC) is an important and abundant chemical and physical aspect of stream ecosystems. Urban environments, including infrastructure such as non-permeable concrete and storm drains, change how the landscape conveys water, and therefore DOC, to rivers like the Kalamazoo River. When DOC reaches the river, it interacts with the biogeochemical processes within the river, including within the hyporheic zone. The hyporheic zone is the highly bioreactive, shallow subsurface of the stream bed where stream and groundwaters mix. We hypothesized that DOC degradation will vary across different DOC sources. We created a variety of DOC leachates from deciduous leaves obtained across the Kalamazoo River Watershed. Then, we conducted push-pull tests with a solute that included environmental water, leaf leachates, and a conservative tracer to simulate the rapid input of landscape DOC into the hyporheic zone. Samples were withdrawn from the area in regular intervals over approximately four hours, then analyzed for both DOC and Chloride content. We assessed the reaction rates of each different carbon source and have found that rates do appear to vary across sources.