A Model of the FoodWeb Bioaccumulation of PCBs in San Francisco Bay

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A Model of the Food-Web Bioaccumulation of PCBs
in San Francisco Bay Frank A.P.C. Gobas and Jon
A. Arnot School of Resource Environmental
Management Simon Fraser University Burnaby
British Columbia Canada
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Biological effect levels in seals, bird eggs
Human Health Risk levels
End-Point
Concentrations in higher trophic species
Concentrations in sport fish
Concentrations in prey species (food-web)
Target Levels, criteria
Concentrations in Water Sediment
Loadings
Acceptable loadings
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Biota Sediment Accumulation Factor (BSAF)
BSAF CB / CS
Sediment
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Csediment
Cbiota
SFB Food-Web Bioaccumulation Model
Input Model
Output
Cbiota BSAF x Csediment
Log Cbiota log BSAF log Csediment
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Csediment
Cbiota
SFB Food-Web Bioaccumulation Model
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Model Performance Analysis
Model Bias (MB) 10
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Model Uncertainty Analysis
1. Monitoring data
2. Stochastic Analysis Monte Carlo Simulations
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Congener Specific Calculation
Cs, PCB congener 1
Cb, PCB congener 1
Cs, PCB congener 2
Cb, PCB congener 2
Cs, PCB congener 3
Cb, PCB congener 3



Csediment, ?PCB
Cbiota, ?PCB
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Results Model Performance Analysis
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Results Model Performance Analysis
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Results Model Performance Analysis
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Results
Results Model Performance Analysis - ?PCB
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Model Application
Forwards Calculation


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Distributions of ?PCB concentrations in sediments
in the Northern (blue line), Southern (red line)
and Central (green line) sections of San
Francisco Bay as well as the distribution for the
entire Bay (black line) based on a total of 1,284
samples collected at RMP stations between 1999
and 2001.
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Threshold Effect Concentration Immunotoxicity
(Kannan et al. 2000)
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Model Application
Backwards Calculation

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Brown Current Concentration in Sediment Green
Based on NOAEL Red Based on LOAEL Blue
Based on Threshold Effect Concentration Grey
Based on human health hazard (H1) Black Based
Upperbound estimate of 1100,000 excess life time
cancer risk in SFB fish eating humans Yellow
Based on 5 exceedence of the threshold effect
concentration
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Bay-wide geometric mean concentrations
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Conclusions Developed and constructed a food-web
bioaccumulation model of PCBs for San Francisco
Bay (Excel spreadsheet). Tested the model against
empirical field data. Model Bias among species
ranged between 0.83 and 1.35 (for PCB congeners)
and 0.73 and 1.19 (for ?PCB). Ideal 1. Range
of model predicted BSAFs that include 95 of the
observed BSAF values ranges between a factor of 2
to 4 of the mean depending on the species. The
model can be used to set Bay-wide target PCB
concentrations for the sediment of San Francisco
Bay. The model can be further developed to make
more spatially explicit calculations of the
relationship between PCB concentrations in
sediments and biota when information on
migrations routes and corresponding sediment
concentrations become available.
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We thank the many people who have helped us to
bring all the information together for the
development of the model.
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Results Model Performance Analysis - ?PCB
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Model Application
Forwards Calculation


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Results Model Performance Analysis
PCB congeners ?PCB
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Model for uptake, elimination bioaccumulation
of PCBs in organisms other than phytoplankton
algae
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Model Calculations
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Mineralization
OC
Z
f
Algae,Macro-phytes
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1
1
4
0.15
6.5
Suspended solids
1.5
0.058
17.3
Bottom sediments