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Great Lakes Research Session 233 rd ACS National Meeting Chicago, IL March 28, 2007. Mass Balance Models for Persistent, Toxic Bioaccumulative Chemicals (PBTs) in the Great Lakes: Application to Lake Ontario . Joseph V. DePinto LimnoTech Ann Arbor, MI Russell G. Kreis, Jr. U.S. EPA

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Great Lakes Research Session

233rd ACS National Meeting

Chicago, IL

March 28, 2007

Mass Balance Models for Persistent, Toxic Bioaccumulative Chemicals (PBTs) in the Great Lakes: Application to Lake Ontario

Joseph V. DePinto

LimnoTech

Ann Arbor, MI

Russell G. Kreis, Jr.

U.S. EPA

Grosse Ile, MI


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Outline

  • Overview of PBTs in Great Lakes

    • Legacy chemicals

    • Chemicals of emerging concern

  • Chemical Mass Balance Models

  • PBT management in Lake Ontario (LaMP)

    • Development, Calibration/Confirmation of LOTOX2

    • Application of LOTOX2



What is a toxic substance pbt l.jpg
What is a “Toxic” Substance? PBT Lakes

  • Is Persistent in the environment

    • Half-life > 8 weeks in any medium (IJC definition)

  • Tends to be Bioaccumulative

    • Characteristic of hydrophobic substances

    • Often not well-metabolized within organism

  • Elicits a Toxic response in exposed biota


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Critical PBTs in Great Lakes Basin – Legacy Contaminants Lakes

(IJC Virtual Elimination Task Force, 1991)


Typical great lakes legacy toxic substance l.jpg
Typical Great Lakes Legacy Toxic Substance Lakes

  • Historically very high emissions and loadings, followed by significant decrease in loadings through ‘70s and ‘80s

  • Very Hydrophobic

    • Strongly associated with particulate matter

  • Semi-volatile

    • subject to long-range atmospheric transport

  • Very Bioaccumulative

    • Human exposure largely through fish consumption




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Typical Great Lakes Toxic Substance Lakes

  • Historically very high emissions and loadings, followed by significant decrease in loadings through ‘80s and ‘90s

  • Very Hydrophobic

    • Strongly associated with particulate matter

  • Semi-volatile

    • Atmospheric inputs were a significant source of PCBs to Great Lakes in late 1980s

    • subject to long-range atmospheric transport



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Typical Great Lakes Toxic Substance Lake Ontario

  • Historically very high emissions and loadings, followed by significant decrease in loadings through ‘80s and ‘90s

  • Very Hydrophobic

    • Strongly associated with particulate matter

  • Semi-volatile

    • subject to long-range atmospheric transport

  • Very Bioaccumulative

    • Human exposure largely through fish consumption



Biomagnification in lake ontario food web ijc 1987 l.jpg
Biomagnification in Lake Ontario Food Web (IJC, 1987) Lake Ontario

BAF for PCBs in

Lake Ontario lake trout

 6 x 106 L/Kg (ww)



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Chemicals of Emerging Concern in the Great Lakes Reductions

  • Tend to have similar properties as Legacy Contaminants but with recent and/or ongoing environmental release

  • Examples:

    • Polybrominateddiphenylethers(PBDEs) – class of chemicals used as flame retardants, plastics in consumer electronics, wire insulation

    • Perfluoro octane compounds (PFOS/PFOA) – class of chemicals with wide use as surfactants and cleaners, 3M ScotchguardTM, insecticides

    • Pharmaceuticals and Personal Care Products (PPCP) – tremendous number of human and veterinary drugs

  • Links to more information:

    • http://www.epa.gov/oppt/

    • http://www.atsdr.cdc.gov/


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Substance X Reductions

Mass Balance Model Concept

External Loading

System Boundary

Control Volume

Transport In

Transport Out

Transformations/

Reactions

Rate of Change of [X] within System Boundary (dCX/dt) =

(Loading) (Transport) (Transformations)


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Value of Models for PBT Management Reductions

  • Models can help evaluate and measure the success of load reduction programs

    • Provide a reference by forecasting the ramifications of no further action

    • Explain/normalize the small scale, stochastic variability in monitoring data so that longer term, system-wide trends can be seen

    • Explain time trends of long-term monitoring

  • Models can aid assessments for which there is no actual environmental experience

    • Estimate impact of new chemicals

    • Forecast impact of unusual limnological factors (e.g., ANS invasions, major storm events, climate change)

    • More localized system responses to watershed load reductions

  • Models can help guide monitoring programs to be more efficient and effective


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Lake Ontario Lakewide ReductionsManagement Plan (LaMP)

  • GLWQA mandated Lakewide Management Plan (LaMP) in all Great Lakes

    • Lake Ontario LaMP led by Four Party Secretariat

    • EPA-Reg 2, NYS DEC, Environment Canada, Ontario MOE

  • Lake Ontario LaMP identified lakewide beneficial use impairments:

    • Restrictions on fish consumption

    • Degradation of wildlife populations

    • Bird or animal deformities or reproductive problems

    • Loss of fish and wildlife habitat

  • Priority LaMP chemicals

    • PCBs, DDT & metabolites, Dieldrin, Dioxins-Furans, Mirex-Photomirex, Mercury

  • LOTOX2 model develop to help address several management questions for critical pollutants in Lake Ontario


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Toxic Chemical Questions for Lake Ontario Lakewide Management Plan (LaMP)

  • What is the relative significance of each major source class discharging toxic chemicals into Niagara R. and Lake Ontario?

  • What is the role of toxic chemicals existing in sediments of the system?

  • Can changes in major source categories and sediments be quantitatively related to concentrations in the water column and fish?

  • Can observed trends in toxic chemical concentrations over time be explained?

  • How does a regulatory or remediation action affect the water column and fish tissue concentrations at steady-state and over time?


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Information Flow in LOTOX2 Model Management Plan (LaMP)

In situ

Solids Levels

Hydraulic TransportModel

Sorbent Dynamics Model

Chemical Mass Balance Model

Food Chain Bioaccumulation Model

Chemical Loading

LOTOX2 - Time-dependent, spatially-resolved model relating chemical loading to concentration in water, sediments and adult lake trout


Lotox2 chemical mass balance framework l.jpg
LOTOX2 Chemical Mass Balance Framework Management Plan (LaMP)

Atmospheric wet &

dry deposition

Gas phase

absorption

Volatilization

Niagara river

Total toxicant in water column

Outflow

Hamilton Harbor

desorption

Toxicant on suspended particulates

Toxicant in dissolved form

US tributaries

Water Column

Canadian tributaries

sorption

Decay

US direct sources

diffusive

exchange

resuspension

settling

Canadian direct sources

Total toxicant in sediment

desorption

Toxicant on sediment particulates

Dissolved toxicant in interstitial water

Decay

Surficial

Sediment

sorption

Deep Sediment

burial


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N Management Plan (LaMP)

LOTOX2 Segmentation Scheme - plan view

Surface water column

Deep water column

Surface sediment

Projection of water column

to sediment segments


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Toxicant Concentration Management Plan (LaMP)

in

Phytoplankton

(mg/g) (1)

Toxicant Concentration

in

Zooplankton

(mg/g) (2)

Toxicant Concentration

in

Small Fish

(mg/g) (3)

Toxicant Concentration

in

Large Fish

(mg/g) (4)

Bioaccumulation Model Framework

Predation

Depuration

Depuration

Depuration

Depuration

Uptake

Uptake

Uptake

Uptake

“Available” (Dissolved) Chemical Water Concentration (ng/L)

Physical-Chemical

Model of

Particulate and Dissolved Concentrations


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PCB Calibration/Confirmation: Management Plan (LaMP)Historical Simulation








Sediment feedback delays lake trout response all scenarios start at 2000 and run for 50 years l.jpg
Sediment Feedback Delays Lake Trout Response Response Time(all scenarios start at 2000 and run for 50 years)



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Baseline and Categorical Scenarios Response Time(all scenarios start at 2000 and run for 50 years)


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LOTOX2 Findings for Management of PCBs in Lake Ontario Response Time

  • Significant load reductions from mid-60s through 80s have had major impact on open water and lake trout rapidly declining trends through that period

  • Lake is not yet at steady-state with current loads. Time to approximate steady-state with 2000 loads is ~30 years

    • Slower declines through ‘90s are result of sediment feedback

    • Ongoing load reductions take 5-10 years to distinguish from no post-2000 load reductions

  • Point Sources of PCBs are relatively small fraction of current total loading

    • Major non-point sources are upstream lake and atmospheric gas phase absorption

    • At present model cannot address problems in localized areas (tributaries, bays, nearshore areas (AOCs)), where PS reductions will have greatest value


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Questions ? Response Time


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Acknowledgements Response Time

  • USEPA – Region 2 for providing most of the funding for this modeling program and for providing guidance and coordination with data collection activities

  • Lake Ontario LaMP Workgroup members and other Four Party participants for continued support and input, including data collection and sharing

  • Other collaborative investigators during model development process, especially:

    • Dr. Joseph Atkinson, University at Buffalo

    • Dr. Thomas Young, Clarkson University

    • Dr. William Booty, NWRI – Canada

  • USEPA – GLNPO for providing funding for the POM-LOTOX2 linkage project and for providing guidance based on experiences with mass balance modeling programs for other Great Lakes systems



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