- The Issue: Are sediments, air, land, and water sources or pathways of contamination that affect the integrity of the ecosystem?
- What is the Lake Michigan Mass Balance Study?
- Sample Design and Sample Collection
Mercury modeling has been done in two stages. The first stage was a screening level model for total mercury, and the second is a more advanced model, called LM2-Mercury, that will eventually include various mercury species, including methyl mercury. Methyl mercury is the form of mercury that bioaccumulates.
The screening level model helped to guide in the construct of the LM2-Mercury and fulfilled the initial objective for the mass balance of mercury in Lake Michigan. The greatest annual tributary load of total mercury is contributed by the Fox River (kg/y). The major annual source of mercury to the lake is from atmospheric deposition. A significant annual amount of the existing mercury settling out of water is being recycled back into the system.
The LM2-Mercury model is being developed as a modification of the LM2-Toxic model used to model PCBs. Mercury species (such as divalent and methylmercury) are associated with the total suspended solids (TSS) in a fresh water system such as lake and river.
Currently, the total mercury module of the model is under construction. This requires constructing a TSS model to reasonably represent the solids dynamics in Lake Michigan to properly simulate mercury species in the system. TSS refers to biotic carbon, abiotic carbon, clay and silts, or categorized as fine grain size and suspended solids, not including sand.
Work with the model to date has revealed that gross settling, gaseous mercury absorption, dissolved gaseous mercury volatilization and atmospheric wet deposition are the four largest individual fluxes of total mercury for Lake Michigan. Mercury associated with solids cycling and air-water exchange are the two most important processes controlling mercury concentration in Lake Michigan, and the Lake Michigan system is likely not at steady-state for total mercury during the project period and has a net loss in the water column.
Zhang, X. and K.R. Rygwelski. August 2000. A Modeling Framework for Mercury Cycling in Lake Michigan. In: J. Nriagu (Ed.), Proceedings of the 11th Annual International Conference on Heavy Metals in the Environment, The University of Michigan, School of Public Health, Ann Arbor, Michigan. Contribution Number 1127.
Rossmann, R. 2009. Estimation of a historic mercury load function for Lake Michigan using dated sediment cores. 2009 International Association for Great Lakes Research Annual Conference, 18-22 May 2009, Toledo, Ohio, pp. 191-192 of abstracts.
Zhang, X., K. R. Rygwelski, R. Rossmann, and R. G. Kreis Jr. 2009. A mercury transport and fate model for mass budget assessment of mercury cycling in Lake Michigan. 2009 International Association for Great Lakes Research Annual Conference, 18-22 May 2009, Toledo, Ohio, p. 243 of abstracts.
Rossmann, R. 2008. The use of dated sediment cores to describe the history of contaminant loads to systems: a case study of mercury fluxes to Lake Michigan. 2008 Ocean Sciences Meeting, March 2-7, 2008, Orlando, Florida.
Rygwelski, K.R. and X. Zhang. January 2004. An Update on Mercury Loadings, Transport, and Fate in Lake Michigan. Presented at the International Joint Commission International Air Quality Advisory Board Conference, Las Vegas, Nevada. January 26-28, 2004.
Rygwelski, K.R. and R.G. Kreis, Jr. June 2003. An Overview of the Lake Michigan Mass Balance Project: Background, Accomplishments, and Future Work. Presented at the 46th Conference on Great Lakes Research, International Association for Great Lakes Research, DePaul University, Chicago, Illinois. June 22-26, 2003.
Rygwelski, K.R., R. Rossmann, R.G. Kreis, Jr., and W.L. Richardson. May 2002. Linking Great Watersheds and Rivers to Forecast the Impact of Stressors on Large Receiving Waters. Presented at the U.S. Environmental Protection Agency Science Forum 2002: Meeting the Challenges, Washington, D.C. May 1-2, 2002.
Zhang, X. and K.R. Rygwelski. May 2000. Modeling Framework for Mercury Cycling in Lake Michigan. Presented at the 43rd Conference on Great Lakes Research, International Association for Great Lakes Research, St. Lawrence River Institute of Environmental Sciences, Cornwall, Ontario, Canada. May 22-26, 2000.
Zhang, X. and K.R. Rygwelski. August 2000. A Modeling Framework for Mercury Cycling in Lake Michigan. Presented at the International Conference on Heavy Metals in the Environment, School of Public Health, The University of Michigan, Ann Arbor, Michigan.