Mass Balance ModelingThe “Check-book” Analogy.Slide 3Slide 4Mean Summer CirculationPopulation Around the Great LakesLAKE MICHIGANLAKE MICHIGAN FACTSSlide 9North CarolinaSlide 11Mass Budget for Lake MichiganDecline in [PCB] over timeMass Budgets for Lake MichiganInflows in kg / yearOutflows in kg / yearSlide 17Control VolumeInputsMass Balance ModelingOutflowsThe “Check-book” Analogy. Balance = deposits – withdrawsIs a $50 account balance a large amount?The answer depends in part upon a couple factors.Is there a difference between :In: $200 $2000Out: $150 $1950Net: $50 $50The “Check-book” Analogy. Account Balance = deposits – withdrawsRelative 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 CirculationPopulation Around the Great Lakes040 80km85ChicagoSouth Haven 86oo87o88o46o45o44o43o42oGreen BayLAKE MICHIGANLAKE MICHIGAN FACTSLake 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 Michigan1. 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 strategy1. 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, 29-30 December, 1959. ed. Howard J. Fincus. 1962. Washington, D.C. American Association for the Advancement of Science.LAKE MICHIGANLENGTH: 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 yearsNorth CarolinaSURFACE AREA: 53821 sq. miles or 48718 sq miles of landWATER SURFACE AREA:5103 square miles SHORELINE LENGTH (including islands): 3375 miles 2.41 times larger surface area than Lake MichiganRiverineWater-Sediment Exchange ExchangeAccumulationAir-WaterExchangeWet & DryDepositionWaterExchangeExchangeSHELF SEDIMENTDEEP SEDIMENTGeneric Model of Mass Budget Pathwaysfor POPs in Limnic and Marine SystemsInputsMixingWaterExchangeMass Budget for Lake MichiganBurial ? kg/yr Atmos. DepositionWet ? kg/yrDry kg/yr Outflow ? kg/yr Gross Gas Volatilization? kg/yrRiverine ? kg/yr Green Bay ? kg/yrWater 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 timeR2 = 0.980.00.51.01.52.02.51978198019821984198619881990199219941996Concentration (ng/L)199620245[PCB]year = [PCB]1980 - 0.12 ( year - 1980)R2 = 0.88-2-1.5-1-0.500.511978198019821984198619881990199219941996Ln ConcentrationMass Budgets for Lake MichiganMass budgets for PCBs in Lake Michigan: 1991, 1994 and 1994 with urbanatmospheric loadings.1991 1994 1994-UrbanTotal PCB Mass inWater Column (kg)2280 965 965Inputs (kg/year)Riverine 110 45 45from Green Bay 115 115 115Atmospheric Deposition Wet 90 50 100 Dry Aerosol 20 50 1090 Gas Absorption 330 280 510Total Loadings 665 540 1860Outflows (kg/year)to Lake Huron 25 10 10Burial 1530 730 730Net Loss 170 440 440Volatilization 1025 640 640Total Losses 2750 1820 1820Loadings - Losses = -2085 -1280 4091% of inventory-132% of inventory4% ofinventoryInflows in kg / yearWet Deposition1005%Dry Deposition109059%Gross Gas Absorption51027%Riverine452%from Green Bay1156%InflowsOutflowsin kg / yearto L.Huron101%Gross Gas Volatilization64035%Net Sedimentation73040%Net loss44024%OutflowsMass Budget for Lake MichiganBurial 730 kg/yr Atmos. DepositionWet 100 kg/yrDry 1090 kg/yr Outflow 10 kg/yr Gross Gas Volatilization640 kg/yrRiverine 45 kg/yr Green Bay 115 kg/yrWater Column 965 kg in Sediment ~75000 kg ?+ 40 kg/yr net loss from lake440 kg/yr (est.)Gross Gas Absorption510 kg/yr Lake Michigan PCB mass budget in 1994 including influence of urban