Water-quality assessment of part of the Upper Mississippi River Basin, Minnesota and Wisconsin: Trace elements in streambed sediment and fish livers, 1995-96

Trace elements were analyzed in streambed sediment and fish livers in part of the Upper Mississippi River Basin as part of the U.S. Geological Survey’s National Water-Quality Assessment Program. The purpose of this report was to describe the occurrence and distribution of trace elements, describe the relations of concentrations measured to natural and anthropogenic factors, and describe any relation between concentrations in streambed sediment and fish livers. The study unit included the part of the Upper Mississippi River Basin from the river’s source in northern Minnesota to the outlet of Lake Pepin, a natural lake on the river located near Red Wing, Minnesota. Streambed sediment samples were collected from 27 sites located throughout the study unit, and fish were obtained from 25 sites.

The occurrence and distribution of trace elements in streambed sediment were related to land use and the composition of surficial glacial deposits covering the study unit. Concentrations of antimony, arsenic, cadmium, copper, lead, mercury, nickel, and zinc in streambed sediment were primarily related to urban land use. Concentrations of these elements generally were greatest in streambed sediment collected at sites within or near urban areas in the study unit. The greatest concentrations of most of these elements were measured in streambed sediment obtained from Shingle Creek. Lead concentrations in streambed sediment Shingle Creek increased in the downstream direction. This pattern probably reflects the past use of leaded gasoline, pesticides, or paints.

Cadmium concentrations in sediment from the Mississippi River were greatest at Nininger, Minnesota and in Lake Pepin. This pattern suggested that inputs of cadmium into the river were from the TCMA.

Arsenic concentrations were greatest in streambed sediment collected from Cedar Creek, Shingle Creek, and the Vermillion River. Increased arsenic and iron concentrations in sediment from Cedar Creek, the Vermillion River, and the most upstream site on Shingle Creek suggested a local source of sulfide minerals or preferential sorption of arsenic to streambed sediment. The greatest concentrations of mercury were measured in streambed sediment collected from the Mississippi River at Grand Rapids and Minneapolis, Minnesota; Shingle Creek at 46th Street in Minneapolis, Minnesota; the Namekagon River above Spring Lake Creek near Hayward, Wisconsin; the St. Croix River at Hudson, Wisconsin; and the Vermillion River near Empire, Minnesota.

In fish livers, all of the trace elements analyzed were detected except antimony, beryllium, cobalt, and uranium. Trace element concentrations in fish livers generally did not show any pronounced patterns. Ranges for concentrations of arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, and zinc were similar to those measured in 20 other NAWQA studies across the United States. Cadmium concentrations in fish livers were moderately correlated to fish length and weight. There were no relations between trace element concentrations in fish livers and streambed sediment.