Transcript Application of a Mass Balance and Bioaccumulation Model

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
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
1980s Brought Focus on “Toxic Substances”
in the Great Lakes
What is a “Toxic” Substance? PBT

Is Persistent in the environment
–

Tends to be Bioaccumulative
–
–

Half-life > 8 weeks in any medium (IJC definition)
Characteristic of hydrophobic substances
Often not well-metabolized within organism
Elicits a Toxic response in exposed biota
Critical PBTs in Great Lakes Basin –
Legacy Contaminants
(IJC Virtual Elimination Task Force, 1991)
Typical Great Lakes Legacy Toxic
Substance
 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
Typical Historic Pattern of PCB Loadings
Hydrophobic Chemicals Accumulate in Lake
Sediments
Typical Great Lakes Toxic Substance
 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
–
Percent
Contribution of
Atmospheric
Deposition of Dioxin
to Lake Ontario
Typical Great Lakes Toxic Substance
 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
Food Web Bioaccumulation
Biomagnification in
Lake Ontario Food
Web (IJC, 1987)
BAF for PCBs in
Lake Ontario lake trout
 6 x 106 L/Kg (ww)
Fish Concentrations Responded to Chemical
Bans and Load Reductions
Chemicals of Emerging Concern in the
Great Lakes


Tend to have similar properties as Legacy
Contaminants but with recent and/or ongoing
environmental release
Examples:
–
–
–

Polybrominated diphenylethers (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/
Mass Balance Model Concept
External Loading
System Boundary
Control Volume
Substance X
Transport In
Transformations/
Reactions
Transport Out
Rate of Change of [X] within System Boundary (dCX/dt) =
(Loading)  (Transport)  (Transformations)
Value of Models for PBT Management

Models can help evaluate and measure the success of
load reduction programs
–
–
–

Models can aid assessments for which there is no actual
environmental experience
–
–
–

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
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
Lake Ontario Lakewide
Management Plan (LaMP)

GLWQA mandated Lakewide Management Plan (LaMP) in all
Great Lakes
–
–

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
–

Lake Ontario LaMP led by Four Party Secretariat
EPA-Reg 2, NYS DEC, Environment Canada, Ontario MOE
PCBs, DDT & metabolites, Dieldrin, Dioxins-Furans, MirexPhotomirex, Mercury
LOTOX2 model develop to help address several management
questions for critical pollutants in Lake Ontario
Toxic Chemical Questions for Lake Ontario Lakewide
Management Plan (LaMP)
1. What is the relative significance of each major
2.
3.
4.
5.
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?
Information Flow in LOTOX2 Model
Hydraulic
Transport
Model
Chemical
Loading
Sorbent
Dynamics
Model
Chemical
Mass Balance
Model
In situ
Solids Levels
Food Chain
Bioaccumulation
Model
LOTOX2 - Time-dependent, spatiallyresolved model relating chemical loading to
concentration in water, sediments and adult
lake trout
LOTOX2 Chemical Mass Balance Framework
Atmospheric wet &
dry deposition
Hamilton Harbor
US tributaries
Canadian tributaries
Total toxicant in water column
desorption
Toxicant on
suspended
particulates
Toxicant in
dissolved
form
sorption
Decay
US direct sources
Canadian direct sources
Outflow
settling
diffusive
exchange
resuspension
Water Column
Niagara river
Gas phase
absorption Volatilization
Total toxicant in sediment
desorption
Dissolved
toxicant in
interstitial water
sorption
Deep Sediment
burial
Decay
Surficial
Sediment
Toxicant on
sediment
particulates
Surface water column
Deep water column
LOTOX2
Segmentation
Scheme
- plan view
Surface sediment
N
Projection of water column
to sediment segments
Bioaccumulation Model Framework
Predation
Depuration
Toxicant
Concentration
in
Phytoplankton
(mg/g) (1)
Uptake
Depuration
Depuration
Toxicant
Concentration
in
Zooplankton
(mg/g) (2)
Toxicant
Concentration
in
Small Fish
(mg/g) (3)
Uptake
Depuration
Toxicant
Concentration
in
Large Fish
(mg/g) (4)
Uptake
“Available” (Dissolved) Chemical Water Concentration (ng/L)
Physical-Chemical
Model of
Particulate and Dissolved
Concentrations
Uptake
PCB Calibration/Confirmation:
Historical Simulation
Reconstruction of historical PCB Loading
20,000
10
Cg
8
15,000
6
10,000
4
5,000
2
0
1930
0
1940
1950
1960
1970
Year
1980
1990
2000
Atmospheric Gas Phase PCB
Concentration, ng/m 3
Watershed PCB Loading, kg/yr
Load
Model Calibration/Confirmation for Water
Column PCB
Water Column tPCB Concentrations
Concentration, ng/m
3
4000
LOTOX2 base
NYSDEC data
Data (Literature)
LOADS data
Env. Canada (April 2004)
3000
2000
1000
0
1980
1985
1990
1995
Year
2000
2005
Confirmation of Average Surface Sediment
Concentrations by Segment (1998)
PCB Concentration, ng/g
250
Data (1998) with Std.Dev.,
Env. Canada
200
LOTOX2 Results
150
100
50
0
23 24 25 26 27 28 29 30 31 32 33 34 35 36
Segment Number
Model Calibration/Confirmation - Lake Trout
PCB
Model Confirmation 1998-2001
Lake Trout tPCB Concentration,
mg/kg wwt
20
18
Huestis et al., 1996 and Whittle 2003 Data (with Std Dev)
EPA data (with Std Dev)
LOTOX2 Model
De Vault et al., 1996
Whittle 2003 Data (w/ Std Error)
Model Confirmation (Whittle 2003 Data w/ Std Error)
Model Confirmation (EPA Data)
16
14
12
10
8
6
4
2
0
1930
1940
1950
1960
Year
1970
1980
1990
2000
Model Confirmation - Lake Trout PCB
LOTOX2
Huestis et al., 1996 and Whittle 2003 Data (with Std Dev)
EPA data (with Std Dev)
LOTOX2 Model
De Vault et al., 1996
Whittle 2003 Data (w/ Std Error)
Model Confirmation (Whittle 2003 Data w/ Std Error)
OME 2002
Env. Canada
Lake Trout tPCB Concentration,
mg/kg wwt
14
Calibration
Period
12
Confirmation
Period
Forcasting
Period
10
8
6
4
2
0
1975
1980
1985
1990
Year
1995
2000
2005
2010
Management Application of
LOTOX2: Source Category and
System Response Time
Sediment Feedback Delays Lake Trout
Response
(all scenarios start at 2000 and run for 50 years)
2.0
2.0
Base Forecast
Forecast (No
(No Action
Action Scenario)
Scenario)
Base
Scenario_2
Base Forecast
(Natural
(No Action
Attenuation)
Scenario)
Scenario_2
(Natural
Attenuation)
Scenario_8 (Eliminate all loads)
Lake Trout PCB Conc.
(mg/kg wwt)
1.8
1.8
1.6
1.6
1.4
1.4
1.2
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
1990
2000
2000
2010
2010
2020
2020
Year
Year
2030
2030
2040
2040
0.0
2050
2050
Influence of Sediment Feedback
Baseline and Categorical Scenarios
(all scenarios start at 2000 and run for 50 years)
2.0
2.0
Base Forecast
Base
Forecast
Base
BaseForecast
Forecast
Base
Forecast
Scenario 7a (Zero
all Point Sources)
Scenario 7a (Zero all Point Sources)
Base
Scenario
Scenario
7b (Scenario
7a (Zero
7a
all+Forecast
Point
Zero Sources)
all tributaries)
Scenario 7b (Scenario 7a + Zero all tributaries)
Scenario 7c (Scenario 7b + Zero Niagara River)
Scenario 7a (Zero all Point Sources)
Scenario
(Scenario7b7a+ +Zero
ZeroNiagara
all tributaries)
Scenario
7c7b(Scenario
River)
Scenario
7d (Scenario
7c + Zero all atmospheric
loads)
1.8
1.8
Lake Trout PCB Conc.
Lake Trout PCB Conc.
(mg/kg wwt)
(mg/kg wwt)
1.6
1.6
1.4
1.4
2.0
2.0
1.8
1.8
1.6
1.6
1.4
1.4
1.2
1.2
1.2
1.2
1.0
1.0
1.0
1.0
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.0
0.0
1990
1990
2000
2000
2000
2010
2010
2010
2020
2020
2020
Year
Year
Year
2030
2030
2040
2040
2040
0.0
0.0
2050
2050
2050
LOTOX2 Findings for Management of
PCBs in Lake Ontario


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
Acknowledgements



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
Gulls Biomagnify PCBs from Fish