Sediments found in waterways around the world may contain toxic compounds of anthropogeilic origin that can harm the environment and human health. As a result, it is often necessary to remove them and find disposal methods that are environmentally and economically acceptable. Here, we report on results obtained in an experimental program to characterize the nature of the sediment contamination. The objective was to gain a better understanding of the properties of the sediments to develop better methods for understanding the fate and transport of the contaminants and for improving methods for their removal from the sediments. Our investigations made use of x-ray facilities at the Brookhaven National Synchrotron Light Source (NSLS) and the European Synchrotron Radiation Facility (ESRF) at Grenoble, France. The experiments included: measurements of the microstructure of the sediments using computed microtomography, x-ray absorption, and fluorescence microscopy with resolutions as low as 0.2 micrometers to obtain information on the relationships of organic and mineral components of the sediments and on the distribution of contaminants on the surfaces of the sediment grains, investigation of functional groups of chemical compounds using x-ray absorption near-edge spectroscopy (XANES) and Fourier Transform Infrared Spectroscopy (FTIR). Scanning electron microscopy (SEM) and electron probe measurements were made to ascertain the morphology of the sediment surfaces and the distribution of metals on individual sediment grains.