GLERL 2004 Milestone Reports

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GOAL: Protect, Restore and Manage Use of Ocean and Coastal Resources Through Ecosystem Management Approaches

NOAA Performance Measure: Increased numbers of techniques and tools that can be used to restore and protect ocean, coastal, and Great Lakes resources.

OAR Performance Measure: Increase the number of sediment core analyses used to estimate the major removal pathway of PCBs (and most other contaminants) from Lake Michigan. Baseline: 4 cores used Target: 40 cores used.

Milestone: Finalize measurements and calculations for the current rates of sediment inventory of PCB's in Lake Michigan.

Purpose: The Lake Michigan Mass Balance (LMMB) Program, designed to test whether contaminant process models would provide useful support in management strategies for the Great Lakes. The major source and sink of several contaminants in the Great Lakes are sediment-water exchange from the large inventory of constituents stored in active sediments and the permanent removal rate of materials into the sediments. These values are critical in overall modeling efforts. The data and synthesized rates were derived as part of a Clean Air Act program.

Efforts and Results (to date): From 1994-96, GLERL scientists, partially supported by EPA, collected and analyzed 123 sediment cores for a number of constituents. Fifty-six of these cores were sliced in 1cm intervals and analyzed for 210Pb and 137Cs to provide a comprehensive geochronology for the lake as a whole and would allow for the calculation of whole-lake sediment, and associated contaminant, accumulation rates. Prior to the initiation of the EPA-sponsored LMMB program, the best available values were used to estimate the fluxes of PCBs. Sediment recycling and removal rates were very large relative to other fluxes (tributary inputs, atmospheric deposition, etc). Those sediment fluxes were based on only 4 cores analyzed for geochronology and PCBs. These values, along with those based on the extensive work done over the past several years are shown in the table.

**Table 1**. Fluxes and inventories of PCBs in Lake Michigan. Units are Kg PCB/y
Process	1991 Best Estimate	Current Values
Burial	1800	350
‘Active sediment inventory’ (Kg)	4500	7100
Sediment resuspension	6500	1150
Settling	7000	950
External load	1050	750

Customers: EPA, who led the program and is using the results as part of bi-national modeling efforts to examine management alternatives for the Great Lakes. Also, any others who model lake mass balances.

Cause Factors (if milestone not met): N/A

Revised Completion Date (if milestone not met): N/A

Last updated: 2004-10-05 js