Trace Metal Concentrations in Surface Sediments of Nine Minnesota Northern Lakes and Forests Ecoregion Reference Lakes

Elevated metal concentrations in sediments may have adverse effects on resident benthic and aquatic organisms. Contaminated sediments may also limit the recreational uses of affected waters. Metals in aquatic sediments occur naturally and as a result of anthropogenic inputs. They may be discharged directly to a waterbody, to a tributary to the waterbody, or emitted to the air and subsequently deposited in the waterbody or its watershed via wet and dry atmospheric deposition. There are several approaches to evaluating sediment metal concentrations. Many of these approaches are summarized in Persaud et al. (1990) and include the following three general approaches: estimating the naturally occurring background concentration of metals, using experimental and/or field data to develop metal concentration-biological effect relationships and using equilibrium partitioning to estimate the bioavailable metal concentration by measuring concurrent metal and sulfide concentrations and predicting toxicity from the estimated porewater concentrations. Comparing measured sediment concentrations against background metal concentrations in sediments of unimpacted, ambient waterbodies is a relatively simplistic approach which implies that concentrations above the background are detrimental. This is not necessarily the case as many metals are bound by components of the sediment such as sulfides"