SEDIMENTOLOGICAL AND GEOCHEMICAL CHARACTERIZATION OF EAST POND, BELGRADE LAKES WATERSHED, CENTRAL MAINE

An interdisciplinary research program (Geology and Chemistry) at Colby College, Waterville, Maine, is developing a model for surface and groundwater interactions over spatial and temporal scales in the Belgrade Lakes watershed. The watershed is a system of seven glacially formed, interconnected lakes in central Maine. Surface and groundwater discharges from the area to the Kennebec River, which empties into the Gulf of Maine.

The present study focuses on East Pond, the head of the lake-chain system. East Pond is roughly oval in shape with several coves along the margins; it has a surface area of ~4500 hectares, a maximum depth of 7.5 m, and an estimated total volume of 33.68 x 10⁶ m³. The lake is surrounded by North temperate hardwood forest and there is a marshy outlet to the other lakes in the northwest corner. This project will develop a baseline for the geological, geo-chemical and hydro-chemical parameters to better understand the lake’s dynamics. Analyses include: characterization of the sedimentology, measurement of the Total Organic Carbon (TOC) and Total Organic Nitrogen (TON) loads, and measurement of the reactive phosphorous on a real-time basis throughout the ice-free months. The lake is characterized by a grain-size of predominantly medium silt (Mean=4.87 Φ) with a range of 1.0 to 6.0 Φ. No clay-sized particles (>8Φ) have been detected in lake-bottom sediment samples. Medium-grained sand occurs at the outlet and very fine sand is restricted to the margins. TOC values range from 1.31% to 26.64% (Mean=5.38%) and the mean TOC:TON ratio is 12.61, indicating a mixed algal and terrestrial origin for organic matter. Phosphorous concentrations from sediment pore waters and water column samples are expected to be high, because the lake has sustained yearly algal blooms. All data will be integrated to evaluate the processes operating within this lake, and a model will be proposed to describe its seasonal dynamics.