1. Dr. Martin T. Auer MTU Department of Civil & Environmental Engineering CE5504 Surface Water Quality Modeling Lab 7. Sediment-Water Exchange Sediments Mediation of the Recovery of Shagawa Lake, Minnesota

2. Depositional Basins Onondaga Lake, NY depositional basin

3. Sediment Diagenesis diagenesis – redox reactions depositionflux

4. Redox Mediation oxic conditions; sparingly soluble anoxic conditions; highly soluble

5. Phosphorus Release Rates

6. Phosphorus Accumulation in the Hypolimnion

7. Engineered Approaches 1. Sediment Removal (Dredging) 2. Hypolimnetic Withdrawal 3. Chemical Inactivation 4. Artificial Circulation 5. Hypolimnetic Aeration 6. Sediment Oxidation Support Raft Gas Vent Support Cables Contact Chamber Air Line & Diffuser Ballast

8. Natural Recovery – The Slow Eigenvalue old SS new SS concentration time for the sediment for the water column

9. Diagenesis and Recovery – Part I

10. Diagenesis and Recovery – Part II

11. Diagenesis and Recovery – Part III

12. Modeling Sediment – Water Interactions 8 load outflow deposition release burial

13. The Limiting Nutrient Concept The Supplies The Product

14. The Limiting Nutrient Controversy

15. Shagawa Lake

16. eutrophic system tertiary treatment installed in 1973 load reduction of 80%

17. Shagawa Lake The (un)response

18. Shagawa Lake A mathematical model predicted that the lake would reach equilibirium P levels of 12 ppb in ~1.5 years. The fact that it didn’t was attributed to sediment P feedback, primarily during summer. Modification of the model to accommodate sediment P release matches post-treatment P levels well and indicates that P release has not been diminished since treatment went on line. Further recovery will depend on the time course of reductions in sediment feedback.