PINE NEEDLE LEACHATE CHEMISTRY FROM A MOUNTAIN PINE BEETLE INFESTED WATERSHED IN SUMMIT COUNTY, COLORADO

The mountain pine beetle (MPB) epidemic in the Rocky Mountains of the United States is a recent indicator of climate change; the implications and remediation strategies of which are still under investigation. Pine needle color is a visual indicator of a MPB infestation. As trees are infected and ultimately die the pine needles change color from a healthy green, to red, to gray. Precipitation and snowfall can cause leaching of pine needles in all infestation stages. An understanding of the evolution of leachate chemistry through the stages of MPB infestation will allow for better prediction of the impact of MPBs on groundwater geochemistry, including a potential increase in soil metal mobilization and potential increases in disinfection byproduct precursor compounds as infestation stages progress. This study uses batch experiments to determine the leachate chemistry of pine needles from trees in four stages of MPB infestation from Summit County, CO, a watershed currently experiencing the MPB epidemic. Each stage of pine needles undergoes four subsequent leach periods in temperature-controlled DI water. The subsequent leaching method adds a second dimension to the experiment by determining how leachate chemistry of each stage changes in relation to contact time with water. The leachate is analyzed for total organic carbon and individual organic compounds present in the leachate are analyzed by UV absorption spectra, fluorescence spectrometry, high-pressure liquid chromatography for organic acid analysis, and size exclusion chromatography. The results will be used to experimentally or numerically model reactions of soil with the leachate as it flows through to the aquifer during precipitation and snowfall events.