INVESTIGATIONS OF URBAN FLOODPLAIN DEPOSITIONAL RATES AND INDUSTRIAL CONTAMINATION ALONG THIRD CREEK IN KNOXVILLE, TN

This abstract describes the results of an ongoing investigation of sedimentation, floodplain disturbance, and contaminant transport along a stream that runs through industrial and urban areas of Knoxville, Tennessee. Urban and industrial contaminants are frequently found in streams and exhibit the potential for transport into adjacent floodplain deposits during seasonal and extreme flood events via sorption onto clays and organic matter. Profiles of undisturbed floodplain deposits were collected using a 5.1 cm diameter auger and 5.1 cm diameter core barrel at four sites along Third Creek. The auger samples were air dried and then split. Grain size distribution, relative age using Cs-137, and organic matter content in the floodplain profiles were obtained from auger samples, and sediment cores were made into thin sections. Thin sections were investigated using the principles of micromorphology to identify anthropogenic indicators such as coal fragments to distinguish flood deposits and buried soil horizons from disturbed sediments and fill materials. Preliminary results from this floodplain sediment characterization showed Third Creek’s floodplain environment to contain sufficient clay and organic matter to suggest the potential for contaminant adsorption and transport to occur. Depositional rates determined from the results of the Cs-137 analysis were used to verify that these floodplains have experienced sufficient sedimentation since the introduction of industrial contaminants into the environment in Knoxville (approx. 150 years ago). A second series of analyses were then performed on the auger samples to determine the presence or absence of industrial contaminants in floodplain deposits. These samples were sent to an external lab and tested for the presence of polycyclic aromatic hydrocarbons (PAHs), lead, mercury, cadmium, and other contaminants. These chemical analyses were also performed on streambed sediment samples. Since adsorption of contaminants onto sediment is proposed to occur in the streambed, if contaminants are found in floodplain deposits, it is likely there will also be evidence of them in streambed sediments.