Synchrotron-based experimental techniques used at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory are 10 to 1,000 times more sensitive than traditional methods, making the APS a crucial resource for environmental-remediation research. A principle public concern is the enormous quantity of mixed radioactive and toxic wastes from the nuclear weapons programs, which pose a long-term threat to our soil, our water supply, and the public health. X-ray techniques in use at the APS enable significant gains in overcoming some of the special challenges of the earth and environmental sciences. Detailed information on the chemical forms of toxic elements is crucial to a complete understanding of this problem, and non-synchrotron research methods lack the sensitivity for study of the relatively small amounts of toxic materials present in a typical sample.