HR: 0830h
AN: H51C-1082    [PDF]
TI: Reconstructing U.S. National Trends in Metals from Reservoir and Lake Sediments, 1970 to Present
AU: * Mahler, B J
EM: bjmahler@usgs.gov
AF: U.S. Geological Survey, 8027 Exchange Dr., Austin, TX 78754 United States
AU: Van Metre, P C
EM: pcvanmet@usgs.gov
AF: U.S. Geological Survey, 8027 Exchange Dr., Austin, TX 78754 United States
AU: Callender, E
EM: ecallender@cox.net
AF: U.S. Geological Survey, 2 Schumann Rd, Westerly, RI 02891 United States
AB: Legislation, regulation, and changing demographics and industrial practices in the United States during the past three decades likely have had an effect on the amount of metals delivered to the environment. To determine whether the combined contribution has resulted in overall increases or decreases in metal concentrations in the environment, the U.S. Geological Survey collected sediment cores from 42 reservoirs and lakes across the country, covering a land-use gradient from undeveloped (reference) to fully urbanized. The cores were subsampled on small intervals and analyzed for a suite of major and trace elements; trends in seven metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) from 1970 to present are discussed here. When all lakes were considered together, statistically significantly downward trends outnumbered statistically significantly upward trends for all metals except Zn. This was most pronounced for Cr and Pb, for which downward trends outnumbered upward trends by 11 to 1. When lakes were classified by land use (reference, light urban, and dense urban) and the three groups tested separately, the results were similar. The number of lakes for which the probable effect concentration was exceeded varied by metal, from just 2 percent of lakes for Cd to 42 percent of lakes for Pb. Concentrations of individual metals increased greatly with urban land use and most often exceeded the probable effect concentration at dense urban sites. These results indicate that overall contamination of United States streams and lakes by metals is decreasing, but even so, current concentrations continue to be at levels that could pose a threat to aquatic biota.
DE: 0345 Pollution--urban and regional (0305)
DE: 1065 Trace elements (3670)
DE: 1803 Anthropogenic effects
DE: 1857 Reservoirs (surface)
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2003 Fall Meeting