THE USE OF CS-137 AS AN ISOTOPIC TRACER TO DETERMINE SEDIMENTATION RATES ON REELFOOT LAKE, NORTHWEST TENNESSEE

Sedimentation rates on Reelfoot Lake in Northwest Tennessee have historically been a concern to stakeholders with recreational, economic, and environmental interests in the region. Five vibracores were collected from the Upper Blue Basin of Reelfoot Lake in June 2012 with the goal of using gamma spectrometer data for Cesium-137 activity as an isotopic tracer for sedimentation rate determination. Established Cs-137 chronostratigraphic markers were identified for the 1954 and 1964 horizons within each core collected. Simple rate calculations for the average sedimentation rate yielded aggradation of 0.71 cm/yr over the 58 year span and 0.53 cm/yr for the 48 year span for the basin. Previous studies conducted in 1984 yielded an average sedimentation rate of 1.7 cm/yr and a comparison with these studies suggests that the sedimentation rate for the Upper Blue Basin (UBB) has, on average, decreased by 61% over the past 28 years. The reduction in the sedimentation rate indicates that ongoing conservation and management efforts within the Reelfoot Lake watershed have reduced erosion and sediment input into the UBB. The use of Cs-137 as an isotopic tracer for lacustrine sedimentation suggests that the overall effect of the net reduction in sedimentation rate has increased the longevity, and likely the ecological health, of the Upper Blue Basin.