Occurrence and Distribution of Selected Trace Elements in Bed Sediment and Fish Tissue in the Upper Colorado River Basin, Colorado, 1995-96
By Jeffrey R. Deacon and Nancy E. Driver
Natural and human factors have affected water quality and biological communities in streams of the Upper Colorado River Basin in Colorado. Bed-sediment and fish-tissue samples were collected in fall 1995 and 1996 to determine the occurrence and distribution of selected trace elements in the basin. Thirty-six sites were sampled for trace elements in bed sediment, and fourteen of these sites were sampled for trace elements in fish tissue. In mining areas of the basin, bed-sediment concentrations of trace elements, such as arsenic, cadmium, copper, lead, and zinc, exceeded current Canadian guidelines for severe effect levels (SEL) on sediment-dwelling organisms. Fish-tissue concentrations for these elements also were high in streams that drain mined areas. Bed-sediment concentrations of several trace elements in areas of urban and mixed land uses and at background sites exceeded the concentrations for the lowest effect level (LEL) on sediment-dwelling organisms. Trace-element concentrations in fish tissue were mid-range compared to all trace-element concentrations for these same land-use categories. High concentrations at background sites indicate that natural geologic conditions can affect trace-element concentrations. Concentrations of trace elements at agricultural sites were low compared to other land-use settings.
KEY TERMS: water quality; trace elements; bed sediment; fish tissue; Colorado