Control Volume Inputs Mass Balance Modeling Outflows

The “Check-book” Analogy. Balance = deposits – withdraws Is a $50 account balance a large amount? The answer depends in part upon a couple factors. Is there a difference between : In:$200$2000 Out:$150$1950 Net:$50$50

The “Check-book” Analogy. Account Balance = deposits – withdraws Relative importance of inflows and outflows depends upon how much $ you’ve got in the account and the size of both inputs and outflows relative to this amount.

Mean Summer Circulation

Population Around the Great Lakes

km 85 Chicago South Haven 86 oo 87 o 88 o 46 o 45 o 44 o 43 o 42 o Green Bay LAKE MICHIGAN

LAKE MICHIGAN FACTS Lake Michigan is the third largest Great Lake by surface area and the sixth largest freshwater lake in the world. Many rivers and streams flow into Lake Michigan, and the major tributaries are the Fox-Wolf, the Grand and the Kalamazoo. There is a diversion from the lake into the Mississippi River basin through the Illinois Waterway at the Chicago River. Small lunar tidal effects have been documented for Lake Michigan 1. Internal waves (upwellings) can produce a 15 degree C. water temperature decrease along the coast in only a few hours, requiring drastic alterations in fishing strategy 1. The northern part of the Lake Michigan watershed is covered with forests, sparsely populated, and economically dependent on natural resources and tourism, while the southern portion is heavily populated with intensive industrial development and rich agricultural areas along the shore. The world's largest freshwater dunes line the lakeshore. 1. Ayers, John C. "Great Lakes Waters, Their Circulation and Physical and Chemical Characteristics," in Great Lakes Basin: A symposium presented at the Chicago Meeting of the American Association for the Advancement of Science, December, ed. Howard J. Fincus Washington, D.C. American Association for the Advancement of Science.

LAKE MICHIGAN LENGTH: 307 miles / 494 km. BREADTH: 118 miles / 190 km. AVERAGE DEPTH: 279 ft. / 85 m MAXIMUM DEPTH: 925 ft. / 282 m. VOLUME: 1,180 cubic miles / 4,920 cubic km. WATER SURFACE AREA: 22,300 sq. miles / 57,800 sq. km. TOTAL DRAINAGE BASIN AREA: 45,600 sq. miles / 118,000 sq. km. SHORELINE LENGTH (including islands): 1,638 miles / 2,633 km. ELEVATION: 577 ft. / 176 m. OUTLET: Straits of Mackinac to Lake Huron RETENTION/REPLACEMENT TIME: 99 years

North Carolina SURFACE AREA: sq. miles or sq miles of land WATER SURFACE AREA:5103 square miles SHORELINE LENGTH (including islands): 3375 miles 2.41 times larger surface area than Lake Michigan

Riverine Water-Sediment Exchange Accumulation Air-Water Exchange Wet & Dry Deposition Water Exchange SHELF SEDIMENT DEEP SEDIMENT Generic Model of Mass Budget Pathways for POPs in Limnic and Marine Systems Inputs Mixing Water Exchange

Mass Budget for Lake Michigan Burial ? kg/yr Atmos. Deposition Wet ? kg/yr Dry kg/yr Outflow ? kg/yr Gross Gas Volatilization ? kg/yr Riverine ? kg/yr Green Bay ? kg/yr Water Column ? kg in Sediment ~ ? kg ? + ? kg/yr net loss from lake ? kg/yr (est.) Gross Gas Absorption ? kg/yr Lake Michigan PCB mass budget.

Decline in [PCB] over time R 2 = Concentration (ng/L) [PCB] year = [PCB] ( year ) R 2 = Ln Concentration

Mass Budgets for Lake Michigan Mass budgets for PCBs in Lake Michigan: 1991, 1994 and 1994 with urban atmospheric loadings Urban Total PCB Mass in Water Column (kg) Inputs (kg/year) Riverine11045 from Green Bay115 Atmospheric Deposition Wet Dry Aerosol Gas Absorption Total Loadings Outflows (kg/year) to Lake Huron2510 Burial Net Loss Volatilization Total Losses Loadings - Losses = % of inventory -132% of inventory 4% of inventory

Inflows in kg / year

Outflows in kg / year

Mass Budget for Lake Michigan Burial 730 kg/yr Atmos. Deposition Wet 100 kg/yr Dry 1090 kg/yr Outflow 10 kg/yr Gross Gas Volatilization 640 kg/yr Riverine 45 kg/yr Green Bay 115 kg/yr Water Column 965 kg in Sediment ~75000 kg ? + 40 kg/yr net loss from lake 440 kg/yr (est.) Gross Gas Absorption 510 kg/yr Lake Michigan PCB mass budget in 1994 including influence of urban areas.