IDENTIFYING SPATIAL TRENDS IN THE PHYSICAL PROPERTIES OF SEDIMENTS, LAKE LOUISE, GEORGIA

Lake Louise is a coalesced sinkhole lake located in Lowndes County, southern Georgia. Previous studies examining sediments in the lake indicate that construction of a nearby interstate highway in 1957 introduced significant quantities of sediment into the lake, but that the characteristics of the resulting silt layer varies with location. This variability may influence chemical concentrations of lake bottom sediments.

This study examines more than 190 samples collected from three sites across the primary inflow basin of the lake at water depths of 6.1, 5.4, and 4.5 m. Analysis of physical characteristics identify four zones within the uppermost ≈4.5 m of lake sediment. Basal zone I, at least 1.3 m thick, consists of organic rich gyttja with small increases in moisture content and organic carbon concentrations, decreasing dry bulk densities, and no consistent trend in inorganic carbon contents moving up core. Zone II displays less well defined yet opposite trends of declining moisture content and organic carbon concentrations, slight increases in dry bulk densities upwards in the core. The most dramatic changes occur in the silty sediments of zone III, which are characterized by a sharp increase in dry bulk densities, by as much as a factor of 15, and sudden decreases in moisture content, organic carbon and inorganic carbon concentrations. These trends reverse in the upper half of zone III and continues upward through zone IV but at a reduced rate.

Correlations between sites indicate that the thickness and concentrations of sediments in these zones change across the lake, most notably in zone III. This zone is thickest (0.09 m) in the deepest part of the basin, decreases to 0.05 m at intermediate depths, and it is difficult to determine its thickness near the lake side. Sediment densities and inorganic sediment concentrations in zone III also decrease with water depth by as much as a factor of 60. Analyses comparing the spatial variations in physical properties with similar trends in metal concentrations as determined by aqua region digestion and ICP-AES are ongoing.