Mercury mass balance modeling in lake ontario
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

Mercury Mass Balance Modeling in Lake Ontario PowerPoint PPT Presentation


  • 91 Views
  • Uploaded on
  • Presentation posted in: General

Mercury Modeling Workshop, Niagara Falls, NY January 19-20, 2006. Mercury Mass Balance Modeling in Lake Ontario. Joseph Atkinson, James Jensen University at Buffalo Joseph V. DePinto Limno-Tech, Inc. Presentation Outline.

Download Presentation

Mercury Mass Balance Modeling in Lake Ontario

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Mercury mass balance modeling in lake ontario

Mercury Modeling Workshop, Niagara Falls, NY

January 19-20, 2006

Mercury Mass Balance Modeling in Lake Ontario

Joseph Atkinson, James Jensen

University at Buffalo

Joseph V. DePinto

Limno-Tech, Inc.


Presentation outline

Presentation Outline

  • Background and overview of Lake Ontario Mass Balance Modeling in Support of LaMP

    • LaMP modeling needs

    • LOTOX2 development and application

  • Mercury modeling under LOADS

    • Development of Hg sub-model for LOTOX2

    • Preliminary application for available data analysis

  • Recommendations for future work


Lake ontario lakewide management plan lamp

Lake Ontario Lakewide Management Plan (LaMP)

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

    • Lake Ontario LaMP led by Four Party Secretariat

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

  • Resolve lakewide beneficial use impairments as defined in GLWQA

    • Restrictions on fish consumption

    • Degradation of wildlife populations

    • Bird or animal deformities or reproductive problems

    • Loss of fish and wildlife habitat

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


Chemicals of concern for lake ontario

PCBs, chlordane, DDT & metabolites, dieldrin, toxaphene, 2,3,7,8-TCDD-PCDF, mercury, mirex-photomirex, hexachlorobenzene, octochlrostyrene, benzo(a)pyrene, lead, heptachlor/heptachlor epoxide

Chemicals of Concern for Lake Ontario

ortho

meta

Cl

Cl

Cl

para

Cl

2,2',3,4' - Tetrachlorobiphenyl

Typical Toxic Substance is:

  • Hydrophobic

  • Persistent

  • Semi-volatile

  • Bioaccumulative


Toxic chemical questions for lake ontario lakewide management plan lamp

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?


Epa funded lake ontario modeling projects

EPA-Funded Lake Ontario Modeling Projects

  • Long-term plan (UB-NYGLRC)

    • Funded by EPA-Region 2

    • 1996-1997

  • LOTOX2 Development and Improvement (UB-NYGLRC)

    • Funded by EPA-Region 2

    • Two project periods for plan implementation

    • 1997-2000

  • Development of LOTOX2 into management tool (LTI)

    • Funded by EPA-Region 2

    • 2002-2004

  • Linked hydrodynamic-LOTOX2 model (UB/LTI)

    • Funded by EPA-GLNPO

    • 2002-2003

  • Modeling for LOADS (UB/LTI)

    • Funded by EPA-Region 2

    • 2002-2005

  • LOTOX2 PCB Model application for TMDL (UB/LTI)

    • Funded by EPA-Region 2 through GLNPO call

    • Starts January 2006


Modeling approach

Modeling Approach

  • Develop LOTOX2 model (Improve spatial and temporal resolution)

  • Construct spatially-resolved Solids Dynamics Model

    • Long term 137Cs time-dependent mass balance

    • Calibrate solids dynamics with 137Cs tracer

  • Reconstruct historical PCB loadings

  • Calibrate LOTOX2 with historical PCB data

  • Confirmation of LOTOX2

  • Apply LOTOX2 to forecast lake response to load reduction actions


Information flow in lotox2 model

Information Flow in LOTOX2 Model

In situ

Solids Levels

Hydraulic Transport

(POM)

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

LOTOX2 Chemical Mass Balance Framework

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

Canadian direct sources

settling

Total toxicant in sediment

desorption

Toxicant on sediment particulates

Dissolved toxicant in interstitial water

Decay

Surficial

Sediment

sorption

Deep Sediment

burial


Lotox2 segmentation scheme plan view

LOTOX2 Segmentation Scheme - plan view

N

Surface water column

Deep water column

Surface sediment

Projection of water column

to sediment segments


Mercury mass balance modeling in lake ontario

Toxicant Concentration

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


Model calibration confirmation lake trout pcb

Model Calibration/Confirmation - Lake Trout PCB


Baseline and categorical scenarios all scenarios start at 2000 and run for 50 years

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


Lotox2 findings for management of pcbs in lake ontario

LOTOX2 Findings for Management of PCBs in Lake Ontario

  • Significant PCB load reductions from mid-60s through mid-90s

    • Significant open water and lake trout declines through 70s and 80s

    • Slower declines in open waters through ‘90s due largely to sediment feedback

    • Lake trout PCBs not yet at steady-state with current loads. Time to approximate steady-state with 1995 loads is ~30 years.

  • Ongoing load reductions are slower

    • Point Sources of PCBs are small fraction of current total loading but may have localized benefits

    • PCBs in lake trout are already below the New York State guidelines for “eat none” of 1.9 ppm

  • LOTOX2 forecasts suggest that we will not be able to achieve unrestricted lake trout consumption, based on the uniform Great Lakes protocol (0.05 ppm), without virtually eliminating watershed PCB loads and seeing some reduction in atmospheric deposition loading as well


Mercury mass balance modeling in lake ontario

Mercury Model development to enhance LOTOX2 capabilities to analyze LaMP priority pollutantsin Lake Ontario


Hg modeling approach

Hg Modeling Approach

  • Develop Hg Sub-model

    • Develop conceptual model for Hg in Lake Ontario

    • Write mass balance equations for each state variable

    • Conduct literature review to develop initial model parameterization

    • Preliminary analysis – sensitivity and data needs

  • Incorporate Hg Sub-Model into LOTOX2

    • Uses same water and solids transport

    • Extend number of state variables (4 for Hg, instead of 1, as for PCBs)

    • Include Hg chemical reactions (not just first order)

    • Modify interphase mass transfer functions (species specific)

  • Compile loading and boundary condition data

    • Uses data from LOADS and literature

  • Conduct model testing and preliminary calibration to available in-lake data

  • Conduct diagnostic analysis to identify and prioritize additional data needs


Conceptual model

Conceptual model

: Non-equilibrium reaction

: Equilibrium reaction

: Exchange

: Settling and Burial

: State variables

Deposition

Atmosphere

Volatilization

Volatilization

Loading

Outflow

Epilimnion

Hg(0)

Bioaccumulation

Hg(II) solids

Hg(II)

MMHg

Bio-Hg

DMHg

Hg(0)

Hypolimnion

Bioaccumulation

Hg(II) solids

Hg(II)

MMHg

Bio-Hg

DMHg

Sediment

Hg(II) solids

Hg(II)

MMHg

DMHg

Burial

(3 sediment layers)


Bioaccumulation

Bioaccumulation

Bioconcentration (direct uptake)

Phytoplankton

1

Zooplankton

2

Small Fish

3

Large Fish

4

MMHg

Biomagnification

Same framework as for PCBs – parameterized for lake trout in 4th level

Physical-chemical model of

(particulate and) dissolved concentrations


Mercury mass balance modeling in lake ontario

Data

  • Much uncertainty in loading data

  • “Preliminary” loading estimates from 2004 Lake Ontario LaMP:

    • Upstream: 75%

    • Point discharges: 10%

    • Atmospheric deposition: 10%

    • Tributaries: 5%

  • “No estimations” of discharge via St. Lawrence River or volatilization (2004 Lake Ontario LaMP)


Summary

Summary


Sensitivity analysis

Sensitivity Analysis

  • Focus on methylation/demethylation rates

    • Widest range in reported values

    • Expected impact on model results most uncertain

    • Variations expected on site-specific basis


Variation in methyl hg with k1 h

Variation in methyl Hg with k1_H

hypolimnion

epilimnion


Summary1

Summary

  • Besides MMHg, little sensitivity found

  • For MMHg, strong sensitivity to both k1 and k2, especially in the hypolimnion

    • Other processes more important in epilimnion

  • Steady state reached for water column concentrations of Hg(0) and Hg(II) after 1 – 2 years

  • Steady water column concentrations of MMHg were reached after about 10 years

  • Sediment concentrations for all species approached steady values only for times approaching 70 years


Ongoing and future work

Ongoing and Future Work

  • Continue testing LOTOX2 with incorporated Hg submodel

  • Recalibrate Hg bioaccumulation portion of the model

  • Long-term runs with variable loading (atmospheric, tributary) – similar to PCB runs

    • Determine extent to which steady conditions exist in the lake

    • Evaluate relative impacts of different sources

  • Continue data collection and site-specific Hg process experimentation


Mercury mass balance modeling in lake ontario

Questions and Discussion


  • Login