Controls on the Stable Isotope Chemistry & Major Ion Fluxes Between Lakes & Groundwaters in a Northern Hardwood, Glaciated Terrain: Short-Term and Long-Term Conseque

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Funding is requested to conduct studies of lake-groundwater interaction using stable isotopic and major ion chemical approaches. Emphasis will be on isotopic variation in del O18 and major ion chemistry (Ca, Mg, Na, K, Cl, SO4, Alkalinity, and pH) in a number of lakes, their surrounding groundwaters, and local atmospheric precipitation. The research area will extend from the existing NSF-LTER North Temperate Lakes research site, a location where extensive biologic, ecological, geochemical, and climatological measurements have been made over the past 10 years, an area in a northern hardwood forest, glaciated terrain with abundant lakes and little drainage integration. Isotope data will be used to calculate hydrologic budgets for lakes and to establish regional gradient in groundwater isotope chemistry according to methods developed for the NSF-LTER lake study. Using these isotope based mass balance estimates we will: a) estimate the average composition of input waters to the lakes; b) understand of the relative role of in lake cycling vs. external lake loading of solutes (especially silica); c) determine natural solute loads to lakes that suffer significant Cl and Na contamination from winter road salt; d) model the composition of waters based on observation of the mineralogic phases that determine the chemistry of the input waters; and e) predict chemical and hydrologic changes that would occur in lakes and groundwaters in response to short-term and long- term climate change. Our studies have implications on the evolution and variations in lake and groundwater chemistry in a broad region of youthful glaciated terrains in temperate regions, and should help us in differentiate the relative importance in lake geochemical cycling vs. external lake loading. From the knowledge of present fluxes of waters to and from lakes and the associated solute loading we intend to model the response of the lake/groundwater chemistry to short-term and long-term variation in climate, and estimate the sensitivity of this important region to such changes.