A sediment record of trace metal loadings in the Upper Mississippi River |
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| Authors: | Steven J Balogh Daniel R Engstrom James E Almendinger Charlene McDermott Jie Hu Yabing H Nollet Michael L Meyer D Kent Johnson |
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| Institution: | (1) Metropolitan Council Environmental Services, 2400 Childs Road, St Paul, MN 55106, USA;(2) St. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St Croix, MN 55047, USA;(3) Present address: Department of Natural Sciences, New Mexico Highlands University, Las Vegas, NM 87701, USA |
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| Abstract: | Sediment cores from Lake Pepin, a natural lake on the Upper Mississippi River, reveal the historical trends in trace metal
use and discharge in the watershed. Lead-210 dated concentration profiles of trace metals (Ag, Cd, Cr, Cu, Hg, Pb, V, Zn)
in sediment cores from throughout the lake generally showed low and stable concentrations prior to settlement (circa 1830),
peak concentrations between 1940 and 1975, and substantial decreases thereafter. Whole-lake sediment accumulation rates increased
greatly over the period of record, from 79,000 metric tons year−1 prior to 1830, to 876,000 metric tons year−1 during the 1990s. Whole-lake accumulation rates of most trace metals peaked in the 1960s but decreased sharply after that.
Sediment and trace metal accumulation rates decreased in the downstream direction, and approximately two-thirds of the sediment
and trace metal mass accumulated in Lake Pepin since 1800 was deposited in the upper 30% (by area) of the lake. The dramatic
declines in trace metal concentrations and accumulation rates in Lake Pepin sediments since 1970 coincide with increased pollution
control and prevention efforts throughout the watershed, including the implementation of secondary treatment at a large municipal
wastewater treatment plant upstream.
This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this
special issue of the Journal of Paleolimnology. D.R. Engstrom served as guest editor of the special issue. |
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| Keywords: | Mississippi River Lake Pepin Lake sediment Trace metals Lead isotopes Wastewater treatment |
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