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Assessment of Sediment Measurements in Lake Michigan as a Case Study: Implications for Monitoring and Modeling
Citation:
MILLER, D. H., R. ROSSMANN, X. XIA, AND W. HUANG. Assessment of Sediment Measurements in Lake Michigan as a Case Study: Implications for Monitoring and Modeling. Presented at 5th International Conference on Remediation of Contaminated Sediments, Jacksonville, FL, February 02 - 05, 2009.
Impact/Purpose:
These results have implications for characterization, monitoring and modeling sediment-water interaction as related to eutrophication, as well as to contaminant exposure and bioaccumulation for chemicals both within Lake Michigan and other large water bodies where stratification of sediment based upon the physics of the system is likely to exist.
Description:
Lake Michigan, the sixth largest freshwater lake in the world by surface area, was utilized as a water body for assessment within a case study. Field data collected at 116 sediment sampling sites throughout the lake in an intensive monitoring effort were utilized for assessment of the distribution of sediment measurements at these sites. Carbon particles act as a carrier for many toxic chemicals dependent upon a given chemical’s hydrophobicity. Human health risks and ecological risk assessment from exposure to contaminants (such as PCBs in Lake Michigan) that reside in and cycle between lake sediments and the overlying water column have been evaluated using carbon-based models representing the toxic contaminant within the water body. In addition, algae populations comprise the base of the food chain, and represent a large biomass in the food web that is capable of making a significant contribution to the cycling of both nutrients and carbon and to biomagnification of contaminants. A precise estimation of the nutrient flux utilized by algae from sediment sources is critical to understanding contaminant dynamics in large lake systems. In the present study, an assessment of the distribution of sediment nutrient and carbon measurements made within Lake Michigan was completed to recognize strata that are relevant to the interaction with the hydrodynamics of the system. Nonparametric comparison tests revealed that significant differences exist between measurements of sediment nutrients and carbon in the lake using strata based upon water depth (all results demonstrated a p<0.01, á=0.05). Cross validation analysis was applied to the field collected samples and revealed that large errors occur when estimating sediment flux of carbon or nutrients at a given location in the lake without considering stratification of the distributions of these measurements. Errors in estimating sediment concentrations specific to a given location in the lake increased to as much as 1300% when stratification of sediment measurements of nutrients and carbon were not employed among sites. These results have implications for characterization, monitoring and modeling sediment-water interaction as related to eutrophication, as well as to contaminant exposure and bioaccumulation for chemicals both within Lake Michigan and other large water bodies where stratification of sediment based upon the physics of the system is likely to exist.