ENVIRONMENTAL CORRELATIONS BETWEEN SURFACE SEDIMENT TRACE METAL CONCENTRATIONS AND LIMNOLOGIC VARIABLES DURING FLOOD CONDITIONS IN 30 WHITE RIVER OXBOW LAKES, AR

The White River, AR, is a major tributary to the Mississippi River and experienced two 100-year flood events during spring 2008. The magnitude of these flooding events has prompted interest in gaining a better understanding of flood frequencies and magnitudes in the region. A collaborative effort is currently underway to quantify water column properties and sediment proxies from oxbow lakes in the lower White River basin collected in the spring and summer of 2008. Calibrated proxies should ultimately allow reconstructions of Late Holocene White River paleoflood events from dated oxbow lake sediment cores.

This particular contribution investigated the relationship of surface sample trace metal concentrations from 30 oxbow lakes with physical and environmental variables observed in the lakes shortly after the 2008 flooding event. Samples were prepared using EPA Method #3050b. Metals (Cu, Cr, Pb, Mn, Ni, and Zn) were quantified using a Perkin Elmer AAnalyst 300 flame atomic absorbance spectrometer and concentrations were reported as parts per million based on wet weight of sediment.

Significant correlations were calculated between the six metals analyzed and a number of environmental variables. Turbidity was correlated to Pb and Cr, likely due to sorption onto particles introduced via flooding. A significant negative correlation was calculated between Zn and distance between the river and lake, suggesting that the river is a primary source for Zn to many of the oxbow lakes. Pb had significantly greater concentrations in the spring, immediately following the flood, as opposed to later in the summer, suggesting that Pb may respond relatively rapidly to changing environmental conditions. This behavior is supported with significant correlations (negative) between Pb and alkalinity and pH. The only element correlated to lake surface area was Pb (positive), suggesting that atmospheric deposition may be a significant transport mechanism for this metal. The results to date are encouraging and suggest that trace metals may become a valuable source of proxy information for paleoflood reconstructions from the lower White River basin.