Deposition and chemistry of bottom sediments in Cochiti Lake, north-central New Mexico

Bottom sediments were sampled at seven sites in Cochiti Lake in
September 1996. Sediment cores penetrating the entire lacustrine
sediment sequence were collected at one site near the dam.
Surficial sediments were sampled at the near-dam site and six other
sites located along the length of the reservoir. Analyses included
grain size, major and trace elements, organochlorine
compounds, polycyclic aromatic hydrocarbons (PAH's), and
radionuclides. Concentrations of trace elements, organic compounds,
and radionuclides are similar to those in other Rio Grande
reservoirs and are low compared to published sediment-quality
guidelines. Most elements and compounds that were detected did
not show trends in the age estimated sediment cores with the
exception of a decreasing trend in total DDT concentrations from
about 1980 to 1992. The mixture of PAH's suggests that the increase
is caused by inputs of fuel-related PAH and not combustion-
related PAH.