Changes in selected metals concentrations from the mid-1980s to the mid-2000s in a stream draining the Picher mining district of Oklahoma

William J. Andrews, Jason R. Masoner, Oklahoma Water Science Center, U.S. Geological Survey The abandoned Picher mining district of northeastern Oklahoma was the largest source of lead and zinc in the world in the 1920s. After abandonment in the late 1960s, the district continued to be affected by severe environmental degradation, such as subsidence and metals such as cadmium and lead seeping from flooded underground mine workings and seeping and running off from as much as 60 million tons of mine tailings remaining at the land surface.