A national assessment of trends in metals and hydrophobic organic contaminants in streams and rivers
of the United States using lake and reservoir sediment cores.
The Contaminant Trends in Lake Sediments (CTLS) Project is part of the U.S. Geological Survey’s National
Water-Quality Assessment Program (NAWQA). The program began in 1991 with the purpose
of producing a long-term assessment of the status of and trends in the quality of the Nation’s water resources. Trends in water-
quality is one of the highest-priority issues for NAWQA.