a model of the food-web bioaccumulation of pcbs in san francisco bay frank a.p.c. gobas and jon a....
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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
Biological effect levels in seals, bird eggs
Human Health Risk levels
Concentrations in prey species (food-web)
Concentrations in higher trophic species
Concentrations in sport fish
Concentrations in Water & Sediment
Loadings
End-Point
Acceptable loadings
Target Levels, criteria
Biota Sediment Accumulation Factor (BSAF)
BSAF = CB / CS
Sediment
Shiner surfperch
SedimentSediment
Amphipod
Jacksmelt
White croaker
Bivalve
Shrimp
PolychaetePhytoplankton
Yellowfin goby
Zooplankton
Mysid
Plainfin midshipman
Harbor seal
Double-crested cormorant
Shiner surfperchShiner surfperch
SedimentSedimentSedimentSedimentSediment
AmphipodAmphipod
JacksmeltJacksmelt
White croakerWhite croaker
BivalveBivalve
ShrimpShrimp
PolychaetePolychaetePhytoplanktonPhytoplanktonPhytoplankton
Yellowfin gobyYellowfin goby
ZooplanktonZooplankton
MysidMysid
Plainfin midshipmanPlainfin midshipman
Harbor sealHarbor seal
Double-crested cormorantDouble-crested cormorant
SFB Food-Web Bioaccumulation
Model
Csediment Cbiota
Input Model Output
Cbiota = BSAF x Csediment
Log Cbiota = log BSAF + log Csediment
SFB Food-Web Bioaccumulation
Model
Csediment Cbiota
Shiner surfperch
SedimentSediment
Amphipod
Jacksmelt
White croaker
Bivalve
Shrimp
PolychaetePhytoplankton
Yellowfin goby
Zooplankton
Mysid
Plainfin midshipman
Harbor seal
Double-crested cormorant
Shiner surfperchShiner surfperch
SedimentSedimentSedimentSedimentSediment
AmphipodAmphipod
JacksmeltJacksmelt
White croakerWhite croaker
BivalveBivalve
ShrimpShrimp
PolychaetePolychaetePhytoplanktonPhytoplanktonPhytoplankton
Yellowfin gobyYellowfin goby
ZooplanktonZooplankton
MysidMysid
Plainfin midshipmanPlainfin midshipman
Harbor sealHarbor seal
Double-crested cormorantDouble-crested cormorant
Model Performance Analysis
Model Bias (MB) = 10
BSAF predicted BSAF observed
m
i m
BSAFBSAF iOiP
jMB 1
log ,,
10*
m
i m
BSAFBSAF iOiP
jMB 1
log ,,
10*
Log (BSAF predicted,i
BSAF observed,i) / n
i=1
n
Model Uncertainty Analysis
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
-3 -2 -1 0 1 2 3
log (Model Bias)
Re
lati
ve
Fre
qu
en
cy
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
-1 0 1 2 3 4 5
log (BSAF)
Re
lati
ve
Fre
qu
en
cy
0
0.02
0.04
0.06
0.08
0.1
0.12
-1 0 1 2 3 4 5
log (BSAF)
Re
lati
ve
Fre
qu
en
cy
1. Monitoring data
2. Stochastic Analysis : Monte Carlo Simulations
Cs, PCB congener 1 Cb, PCB congener 1
Congener Specific Calculation
Cs, PCB congener 2 Cb, PCB congener 2
Cs, PCB congener 3 Cb, PCB congener 3
Csediment, PCB Cbiota, PCB
+**
Results: Model Performance Analysis
Jacksmelt - SFB
-1
-0.5
0
0.5
1
1.5
28 18 28 31 33 44 49 52 56 60 66 70 74 87 95 97 99 101
105
110
118
128
132
138
141
149
151
153
156
158
170
174
177
180
183
187
194
195
201
203
PCB Congener
log
BS
AF
(k
g/k
g)
Predicted
Observed
Results: Model Performance Analysis
Cormorant Egg
0
0.5
1
1.5
2
2.5
3
3.5
48 18 28 31 33 44 49 52 56 60 66 70 74 87 95 97 99 101
105
110
118
128
132
138
141
149
151
153
156
158
170
174
177
180
183
187
194
195
201
203
PCB Congener
log
BS
AF
(k
g/k
g)
Predicted
Observed
Results: Model Performance Analysis
Adult Male Seal
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
58 18 28 31 33 44 49 52 56 60 66 70 74 87 95 97 99 101
105
110
118
128
132
138
141
149
151
153
156
158
170
174
177
180
183
187
194
195
201
203
PCB Congener
log
BS
AF
(k
g/k
g)
Predicted
Observed
Results:Results: Model Performance Analysis - PCB
0 0.5 1 1.5 2 2.5 3 3.5 4
Shiner surfperch
Jacksmelt
White croaker
DC Cormorant Egg
Forster's Tern Egg
Male Harbor Seal
Female Harbor Seal
log BSAF (kg - dw sed / kg - ww biota)
Observed Predicted - 95% MCS
0 1 2 3 4 5
log (BSAF)
Model Application
Forwards Calculation
0
0.05
0.1
0.15
0.2
0.25
0.3
-1 0 1 2 3 4
log SUM SFEI PCB (u g/kg dry wt) in sediment
Fre
qu
ency
SFB Food-Web Bioaccumulation
Model
0 1 2 3 4 5 6
log (CB)
+ =
0
0.05
0.1
0.15
0.2
0.25
0.3
-1 0 1 2 3 4
log SUM SFEI PCB (u g/kg dry wt) in sediment
Fre
qu
ency
0
5
10
15
20
25
-1 0 1 2 3 4
log SUM SFEI PCB (u g/kg dry wt) in sediment
Fre
quen
cy
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.
White croaker
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4log SUM PCBs (ug/kg)
Pro
babi
lity
Den
sity
Observed
MCS
MB
Adult Male Seal
0
0.05
0.1
0.15
0.2
2 3 4 5 6log SUM PCBs (u g/kg)
Pro
bab
ilit
y D
ensi
ty
Observed
MCS
MB
Adult Male Seal
0
0.25
0.5
0.75
1
2 3 4 5 6log SUM PCBs (u g/kg)
Cu
mu
lati
ve P
rob
abil
ityLOAEL
MCS
MB
Threshold Effect Concentration:
Immunotoxicity
(Kannan et al. 2000)
0 1 2 3 4 5
log (BSAF)
Model Application
Backwards Calculation
SFB Food-Web Bioaccumulation
Model
=
0 1 2 3 4 5
log (CB)
-
-3 -2 -1 0 1 2 3
log (CS)
0 10 20 30 40 50 60 70 80
Shiner surfperch
Shiner surfperch
Jacksmelt
Jacksmelt
White croaker
White croaker
Cormorant Egg
Tern Egg
Male Harbor Seal
Male Harbor Seal
Male Harbor Seal
Male Harbor Seal
Female Harbor Seal
Female Harbor Seal
Female Harbor Seal
Female Harbor Seal
Current Sediment Concentration
SFEI Sum PCB sediment concentration (u g/kg dry)
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 (H=1)
Black: Based Upperbound estimate of 1:100,000 excess life time cancer risk in SFB fish eating humans
Yellow : Based on 5% exceedence of the threshold effect concentration
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5 6
log (Csediment)
Rel
ativ
e F
req
uen
cy
Bay-wide geometric mean concentrations
ConclusionsDeveloped 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.
We thank the many people who have helped us to bring all the information together for the development of the
model.
Organism Criterion
TissueConcentration
SUM PCBs (SFEI)(ug/kg wet weight)
% equal or exceed
Shiner surfperch Human Health Risk – 10-5 Cancer 51.9 81.3
Shiner surfperch Human Health Risk – Threshold 207 31.8
Jacksmelt Human Health Risk - 10-5 Cancer 51.9 26.9
Jacksmelt Human Health Risk – Threshold 207 2.9
White croaker Human Health Risk - 10-5 Cancer 51.9 84.3
White croaker Human Health Risk – Threshold 207 36.3
Cormorant Egg Ecological Risk – LOAEL 5000 17.0
Tern Egg Ecological Risk – LOAEL 4000 10.3
Female Harbor Seal Ecological Risk - Threshold Effect 4730 56.4
Male Harbor Seal Ecological Risk - Threshold Effect 4730 76.3
0 0.5 1 1.5 2 2.5 3 3.5 4
Shiner surfperch
Jacksmelt
White croaker
DC Cormorant Egg
Forster's Tern Egg
Male Harbor Seal
Female Harbor Seal
log BSAF (kg - dw sed / kg - ww biota)
Observed Predicted - 95% MB
Results: Model Performance Analysis - PCB
0 1 2 3 4 5
log (BSAF)
Model Application
Forwards Calculation
0
0.05
0.1
0.15
0.2
0.25
0.3
-1 0 1 2 3 4
log SUM SFEI PCB (u g/kg dry wt) in sediment
Fre
qu
ency
SFB Food-Web Bioaccumulation
Model
0 1 2 3 4 5 6
log (CB)
+ =
Species Name MB (5 - 95% ile) MB* (5 - 95% ile)
California mussels Mytilus californianus 0.97 (0.24 - 3.96) 0.73 (0.38 – 1.41)
Pacific oyster Crassostrea gigas 0.91 (0.23 - 3.58) 0.71 (0.32 – 1.56)
Shiner surfperch Cymatogaster aggregate 1.17 (0.32 - 4.33) 0.97 (0.31- 2.98)
Jacksmelt Atherinopsis californiensis 1.14 (0.48 - 2.72) 0.95 (0.27- 3.39)
White croaker Genyonemus lineatus 1.35 (0.38 - 4.84) 1.02 (0.39 – 2.64)
Double-crested cormorant Phalacrocorax auritus 1.19 (0.44 - 3.21) 0.85 (0.37 – 1.93)
Male harbor seal Phoca vitulina 1.05 (0.72 - 1.54) 1.19 (0.23 – 6.22)
Female harbor seal Phoca vitulina 0.87 (0.47 - 1.63) 0.79 (0.34 - 1.85)
PCB congeners PCB
Results: Model Performance Analysis
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 1 2 3 4 5 6
log (BSAF)
Rel
ativ
e F
req
uen
cy
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
-2 -1 0 1 2 3 4
log (BSAF)
Rel
ativ
e F
req
uen
cy
Model for uptake, elimination & bioaccumulation of PCBs in organisms other than phytoplankton & algae
Gw.Ew.Cw + Gd.Ed.Cd
Cb = Gw.Ew + Gf.Ed + Vb (km +kg)
Kbw Kbf
Model Calculations
26%
4%
1.5%
1
0.15
0.058
1
6.5
17.3
Mineralization
OC Z fAlgae,Macro-phytes
Suspended solids
Bottom sediments