GRAIN SIZE ANALYSIS PRETREATMENTS AND CONTAMINATED SEDIMENT TRANSPORT

A small watershed in Eastern Tennessee has 137Cs adsorbed to fluvial sediment in the drainage channels. An extensive field monitoring program and a contaminant transport model are being used to estimate the off-site transport of the 137Cs on sediment during floods. During the initial model analyses, the distributions of particle size and 137Cs were determined to have a significant impact on simulation results. The selection of a pretreatment method is an important but nonstandard aspect of measuring particle size distributions. Eight pretreatment methods were compared for impact on panicle size distribution and the distribution of 137Cs on particle sizes. The difference in particle size distributions between any two pretreatment methods was less than the difference between the no treatment condition and any of the pretreatments. Most of the pretreatments caused a finer particle size distribution by reducing coarse silt size aggregates. Pretreatments also tended to increase the concentration of 137Cs on clay size particles.