MRI: Integrated Sampling and Analysis Platform for the Investigation of Lake Geochemistry Over a Range of Temporal and Spatial Scales

Colby College, Waterville ME

Investigators

Abstract

0115900 King This Major Research Instrumentation (MRI) award will allow the investigators to assemble a cost-effective and technically sophisticated instrument platform for coordinated biogeochemical investigations in lakes. The platform is based in a Godfrey Marine pontoon boat equipped with: four on-line FIA-based instruments (Fe, H2O2, and nutrient analysis), CTD (temperature, depth, conductivity, pH, eH, O2, fluorescence), GPS navigation, and a vibracoring system. This instrument provides the capability to measure multiple geochemical parameters in the water column and sediments over a range of scales - both temporal (seconds to centuries) and spatial (cm to km). Fieldwork will be concentrated in the Belgrade Lakes, where both general types of Maine lakes coexist and can be compared. The integrated sampling and analysis platform will be used to investigate the spatial and temporal distribution of iron, H2O2,, NO3-, and PO43- in these lakes. Critical to this investigation is an estimate of nutrient inputs from ground waters and historical burial of nutrients as it pertains to internal nutrient loading. Fluid flow through the system will be modeled using Visual MODFLOW software calibrated against actual physical and chemical fluid flow over seasonal, and watershed scales. Vibracores of watershed sediments will be obtained using the platform. Using standard sedimentological techniques a detailed historical record of the transition from marine to freshwater conditions will be developed. Stratigraphic elemental analyses across the basins, reflecting long-term temporal and spatial changes, will be mapped and assessed. Using these data, coupled with similar chemical data obtained on a daily, weekly, monthly, and yearly basis, lake geochemical dynamics will be evaluated over several scales. Student participation is an integral part of this study. Student research assistants will help with all aspects of the project during the summer months. In addition, approximately 40 students a year will actively use the integrated sampling and analysis platform as part of two Geology and two Chemistry courses. Analysis of data over a range of space and time will be used to draw connections between the research projects. Such research efforts will provide the linkages between what students generally consider unrelated disciplines, helping them to recognize that Earth processes are system processes. ***