It is widely known that certain areas of the earth are characterized by such high concentrations of toxic elements that their use by plants or animals is precluded. A water hole whose water contains potentially toxic quantities of As is a common example of such a naturally poisoned area. The dry salt basins of the Basin and Range Province in Nevada and western Utah are largely relict inland salt seas and, because many of the salt basins have total interior drainage of both surface and ground water, these basins represent unique geochemical environments for the entrapment and concentration of mobile elements. Through leaching, transport, and ultimate deposition from throughout the water shed, the closed salt basins are hydrologic sinks in which toxic materials such as As, Sb, Hg, and other heavy metals become concentrated in a relatively confined area.