Muskegon Lake Area of Concern, MI
A preliminary investigation of the nature and extent of sediment contamination in Muskegon Lake was performed using Sediment Quality Triad methodology. Sediment chemistry, solid-phase toxicity, and benthic macroinvertebrates were examined at 15 locations. In addition, three core samples were evaluated using radiometric dating and stratigraphy to assess sediment stability and contaminant deposition. High levels of cadmium, copper, chromium, lead, and mercury were found in the Division Street Outfall area. These levels exceeded the Probable Effect Concentrations (PECs) for current sediment quality guidelines. Most of the heavy metals were found in the top 80 cm of the core samples. Deeper layers of contamination were found only near the former Teledyne foundry and down stream from Ruddiman Creek. High concentrations of PAH compounds were found at a lakeshore industrial area formerly occupied by a manufactured gas facility, an iron foundry, commercial shipping docks, a rail yard, and a coal storage facility. These levels also exceeded PEC guidelines. Sediment toxicity was observed at two stations in the Division Street Outfall area and at the lakeshore industrial site. These locations had the highest concentrations of metals and PAH compounds respectively. Benthic macroinvertebrate communities throughout Muskegon Lake were found to be indicative of organically enriched conditions. The locations in the Division Street Outfall area were significantly different than reference sites with respect to fewer numbers and a smaller population of detritivores. Sediment Quality Triad diagrams were prepared and significant correlations were obtained between chemistry and toxicity and chemistry and diversity (p < .01). Toxicity and diversity also were positively correlated (p < .05). Based on the results of this investigation, the Division Street Outfall and the location down gradient from the lakeshore industrial site are priority areas for further investigation and potential remediation due to adverse ecological effects, toxicity, and high contaminant levels. Stratigraphy and radiometric dating analyses conducted on sediment cores provided important information related to depositional history. Ruddiman Creek appears to have a significant influence on the deposition of heavy metals in the southwestern part of Muskegon Lake. A peak in metals deposition was found that corresponded to the 100+ year flood that occurred in 1986. The historical deposition was considerably higher than current rates. The deep zone off the Car Ferry Dock was not found to be an area that accumulates sediments. High inventories of 210Pb were found near the bottom of this 80 cm core, indicating active mixing and movement of sediments. The presence of elevated metals in the deeper strata plus the high 210Pb inventories suggest that contaminated sediments are moved from the eastern part of Muskegon Lake to this location where they are mixed and made available for resuspension by the currents traveling along the old river channel. The core from the Division Street Outfall showed relatively stable sediments in the top 20 cm followed by a stable zone of heavy accumulation after 1960. Based on these results it is apparent that the removal of contaminated sediments from Ruddiman Creek and the lagoon would reduce the loading of heavy metals to western Muskegon Lake. The areas of high sediment contamination in the eastern part of the lake also appear to be mixed and subject to transport.