overview of tm6: simulation of selenium fate and transport in north san francisco bay limin chen,...
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Overview of TM6:Simulation of Selenium Fate and Transport in North San Francisco Bay
Limin Chen, Sujoy Roy, and Tom GriebTetra Tech, Inc., Lafayette, CA
Presentation to TMDL Advisory Committee
April 28, 2010
Overview Goal: Develop tool to calculate selenium in water and
biota in response to different loads of selenium entering North San Francisco Bay
Technical Review Process
Modeling Approach
Selenium Loads
Example Calibration Results
Predicted Loads and Concentrations
Role of Boundary Conditions
Model Scenarios
Technical Review Committee (2007-2010) Dr. Nicholas S. Fisher, State University of New York,
Stony Brook Dr. Regina G. Linville, California State Office of
Environmental Health Hazard Assessment Dr. Samuel N. Luoma, Emeritus, U.S. Geological Survey Dr. John J. Oram, San Francisco Estuary Institute
The role of the Technical Review Committee was to provide expert reviews of the modeling process as well as credible technical advice on specific issues arising during the review. Final TM-6 report includes their comments and our responses.
Model Structure
Total Particulate Selenium as a Mix of Organic and Inorganic Species (g/g)
Uptake by bivalves
Uptake by predator species
ECoSModel
Results
DYMBAMModel
TTF
SelenateDSe(VI)
SeleniteDSe(IV)
Organic SelenideDSe(-II)
Selenate +Selenite
PSe(IV+VI)
Elemental SePSe(0)
Organic SelenidePSe(-II)
Bed Sediments
Dissolved species
Particulate species
Point Sources (Refineries, POTWs, Other Dischargers)
Contribute primarily to suspended particulates, and to dissolved phase in a limited way
Contribute to dissolved phase
Estuary Water Column
River and Tributary
Loads
SelenateDSe(VI)
SeleniteDSe(IV)
Organic SelenideDSe(-II)
Selenate +Selenite
PSe(IV+VI)
Elemental SePSe(0)
Organic SelenidePSe(-II)
Bed Sediments
Dissolved species
Particulate species
Point Sources (Refineries, POTWs, Other Dischargers)
Contribute primarily to suspended particulates, and to dissolved phase in a limited way
Contribute to dissolved phase
Estuary Water Column
River and Tributary
Loads
Total Particulate Selenium as a Mix of Organic and Inorganic Species (g/g)
Uptake by bivalves
Uptake by predator species
ECoSModel
Results
DYMBAMModel
TTF
SelenateDSe(VI)
SeleniteDSe(IV)
Organic SelenideDSe(-II)
Selenate +Selenite
PSe(IV+VI)
Elemental SePSe(0)
Organic SelenidePSe(-II)
Bed Sediments
Dissolved species
Particulate species
Point Sources (Refineries, POTWs, Other Dischargers)
Contribute primarily to suspended particulates, and to dissolved phase in a limited way
Contribute to dissolved phase
Estuary Water Column
River and Tributary
Loads
SelenateDSe(VI)
SeleniteDSe(IV)
Organic SelenideDSe(-II)
Selenate +Selenite
PSe(IV+VI)
Elemental SePSe(0)
Organic SelenidePSe(-II)
Bed Sediments
Dissolved species
Particulate species
Point Sources (Refineries, POTWs, Other Dischargers)
Contribute primarily to suspended particulates, and to dissolved phase in a limited way
Contribute to dissolved phase
Estuary Water Column
River and Tributary
Loads
ECoS = Fate and transport modeling framework for selenium speciesDYMBAM = Dynamic Bioaccumulation Model for estimating bivalve concentrations TTF = Trophic Transfer Factor, ratio between food and predator tissue concentration
Red dots: approximate locations of model segments
Yellow pins: sampling stations in Cutter and Cutter (2004) survey
Model domain starts at Sacramento River at Rio Vista and extends to Golden Gate
Study Domain
Model Components and Steps in Calibration1. Salinity: relatively conservative (advection and dispersion)2. Total Suspended Material: three components of PSP, BEPS
and phytoplankton, result of advection, dispersion3. Phytoplankton (Chl a): result of advection, dispersion, growth,
respiration, and grazing4. Dissolved selenium: selenite (SeIV), organic selenide (SeII),
selenate (SeVI)5. Particulate selenium: particulate elemental , particulate
organic selenide , particulate adsorbed selenite + selenate
Transformation modeled as first order reactions; transformations include: uptake by phytoplankton, adsorption/desorption, oxidation, mineralization
Modeling Steps
During model calibration, adjustable parameters were varied to obtain a best fit to the data; for evaluation, the model was run with the fitted parameters and compared with new data sets
Model calibrated to data from 1999, and tested against datasets from 2001, 2005, 1998 and 1986
Model applied in a predictive mode using historical hydrology and different load scenarios
Tetra Tech worked with model developers (Shannon Meseck, John Harris) over the course of this work
Model Schematic
Point Sources, Tributaries, and South Bay Input
Sacramento River at Rio Vista
San Joaquin River near
Delta
Seawater Exchange
North San Francisco BayGolden Gate
1-D model with 33 well-mixed cells representing the bay.
Selenium Transformations
SelenateSe(VI)
Organic SelenideSe(-II)
SeleniteSe(IV)
Dissolved SpeciesSelenate+ Selenite
Se(VI)+ Se(IV)
Organic Selenide
Se(-II)
Elemental SeSe(0)
Selenate+ SeleniteSe(VI)+ Se(IV)
Organic Selenide
Se(-II)
Elemental SeSe(0)
Organic SelenideSe(-II)
PSP
Phyto-plankton
BEPS
Mineralization, k1
Uptake, k6
Mineralizatio
n, k 1
Mineralization, k1
Ads/Des, a’, b
Ads/Des,
a’, b
Uptake, k4
Uptake, k5
Oxidation, k2
Oxidation, k3
Advective/Dispersive Exchange with Upper
Cell
Advective/Dispersive Exchange with Lower
Cell
Bed Exchange
Represented by first-order rate constants.
Uptake by Bivalves
Time
Time
Time
Time
Se(0), particulate
Se(IV) + Se(VI),particulate
Se(-II),particulate
AE = 0.2AE = 0.45
AE = 0.54 to 0.8
C. amurensisconcentration
CmsskeCfIRAECwkudtdCmss
Cmss is selenium concentration in tissue (μg/g), ku is the dissolved metal uptake rate constant (L/g/d), Cw is the dissolved metal concentration (µg/L), AE is the assimilation efficiency (%), IR is the ingestion rate (g/g/d), Cf is the metal concentration in food (e.g. phytoplankton, suspended particulate matter, sediment) (µg/g), and ke is the efflux rate (d-1).
Boundary Conditions are Important
0 100Distance
C
Sources in the Bay
Seawater boundary
Riverine boundary
C, on the y-axis, represents a constituent being modeled. The model framework shown on the preceding slides involves the solution of a set of differential equations. These explain the shape of the curve. However, the boundary conditions also have an important effect on determining the actual magnitudes of C.
Year
1985 1990 1995 2000 2005
Se
leni
um
load
s (k
g/yr
)
0
2000
4000
6000
8000
10000
Riverine (kg/yr) Refineries (kg/yr) Tributaries (kg/yr)
Annual Selenium Loads
Dissolved Loads for Water Year 1999
SJR @ Vernalis2666
7%
Delta 365South Bay
1607 176SJR @ confluence POTWs
32% 3%
Sac. River @ Rio Vista Bay Exchange with Ocean Water1502 503430%
Tributaries Refineries820 55916% 11%
Particulate Loads for Water Year 1999
SJR @ Vernalis652
Delta
78 0SJR @ confluence POTWs
11%
Sac. River @ Rio Vista Bay Exchange with Ocean Water465 ~ 754 804 (32 BEPS)
89%
Tributaries Refineries Bed Exchange0 0 0.1
Xcal
Xobs
Xobs
XcalGOF 1*100(%)
Example Calibration 1: Salinity (1999)
Salinity
Observed (psu)
0 5 10 15 20 25 30 35P
red
icte
d (
psu
)0
5
10
15
20
25
30
35
y = 0.9272 x + 1.0404
Jan 21, 1999
Sal
init
y (p
su)
0
5
10
15
20
25
30
35
April 14, 1999
Sal
init
y (p
su)
0
5
10
15
20
25
30
35
May 7, 1999
Sal
init
y (p
su)
0
5
10
15
20
25
30
35
June 7, 1999
Distance (km)
0 20 40 60 80 100
Sal
init
y (p
su)
0
5
10
15
20
25
30
35
August 17, 1999
Sep 14, 1999
Oct 19, 1999
Nov 10, 1999
Distance (km)
0 20 40 60 80 100
r = 1.00GOF = 97.0%
r = 0.98GOF = 99.6%
r = 1.00GOF = 89.2%
r = 0.97GOF = 85.2%
r = 0.99GOF = 98.5%
r = 1.00GOF = 94.9%
r = 1.00GOF = 94.8%
r = 0.99GOF = 97.5%
Example Calibration 2: Chlorophyll a (1999)
Jan 21, 1999
Ch
l a
(g
/L)
0
2
4
6
8
10
12
April 14, 1999
Ch
l a
(g
/L)
0
2
4
6
8
10
12
May 7, 1999
Ch
l a
(g
/L)
0
2
4
6
8
10
12
June 7, 1999
Salinity
0 5 10 15 20 25 30 35
Ch
l a
(g
/L)
0
2
4
6
8
10
12
August 17, 1999
0
2
4
6
8
10
12
Sep 14, 1999
0
2
4
6
8
10
12
Oct 19, 1999
0
2
4
6
8
10
12
Nov 10, 1999
Salinity
0 5 10 15 20 25 30 350
2
4
6
8
10
12
r = 0.31GOF = 68.5%
r = 0.09GOF = 95.2%
r = 0.40GOF = 92.4%
r = 0.47GOF = 86.0%
r = 0.45GOF =66.8%
r = -0.04GOF = 48.2%
r = 0.07GOF = 31.8%
r = 0.83GOF = 82.2%
Chlorophyll a
Observed (g/L)
0 2 4 6 8 10 12 14 16
Pre
dict
ed ( g
/L)
0
2
4
6
8
10
12
14
16
R2 = 0.358
Salinity
0 5 10 15 20 25 30 35
Se
leni
te ( g
/L)
0.00
0.02
0.04
0.06
0.08
0.10
Salinity
0 5 10 15 20 25 30 35
Se
lena
te ( g
/L)
0.00
0.02
0.04
0.06
0.08
0.10
Salinity
0 5 10 15 20 25 30 35
Org
. S
ele
nide
( g
/L)
0.00
0.02
0.04
0.06
0.08
0.10
r = 0.164GOF= 95.0%
r = 0.192GOF = 78.3%
r = 0.353GOF = 95.8%
Example Calibration 3: Dissolved Selenium (1999)
Salinity
0 5 10 15 20 25 30 35
Par
t. S
eIV
+S
eV
I (
g/L)
0.000
0.005
0.010
0.015
0.020
0.025
Salinity
0 5 10 15 20 25 30 35
Par
t. S
e0
(g/
L)
0.000
0.005
0.010
0.015
0.020
0.025
Salinity
0 5 10 15 20 25 30 35
Par
t. S
e-I
I (
g/L)
0.000
0.005
0.010
0.015
0.020
0.025
r = 0.801GOF = 92.1%
r = 0.676GOF = 83.5%
r = -0.021GOF = 73.5%
Example Calibration 4: Particulate Selenium (1999)
TSM Long-Term Evaluation at USGS Stations
STN 3
1998 2000 2002 2004 2006 2008 2010
TS
M (
mg
/l)
0
50
100
150
200
250
ObservedSimulated
STN 6
Year
1998 2000 2002 2004 2006 2008 2010
TS
M (
mg
/l)
0
50
100
150
200
250
ObservedSimulated
STN 14
1998 2000 2002 2004 2006 2008 2010
TS
M (
mg
/l)
0
50
100
150
200
250
ObservedSimulated
STN 18
Year
1998 2000 2002 2004 2006 2008 2010
TS
M (
mg
/l)
0
50
100
150
200
250
ObservedSimulated
Evaluation of Chlorophyll a STN 3
1998 2000 2002 2004 2006 2008 2010
Ch
l a
(g
/l)
0
2
4
6
8
10
12
14
16
18
20
ObservedSimulated
STN 6
Year
1998 2000 2002 2004 2006 2008 2010
Ch
l a
(g
/l)
0
2
4
6
8
10
12
14
16
18
20
ObservedSimulated
STN 14
1998 2000 2002 2004 2006 2008 2010
Ch
l a
(g
/l)
0
10
20
30
40
50
ObservedSimulated
STN 18
Year
1998 2000 2002 2004 2006 2008 2010
Ch
l a
(g
/l)
0
2
4
6
8
10
12
14
16
18
20
ObservedSimulated
Suisun Bay
Suisun Bay
San Pablo Bay
Central Bay
Predicted Particulate Selenium Concentrations (1999)
November 11, 1999
0 5 10 15 20 25 30 35
Par
t. S
eIV
+ S
eVI
(g
/g)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
ObservedPredicted
0 5 10 15 20 25 30 35
Par
t. S
e0 ( g
/g)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20 25 30 35
Par
t. S
eII
(g
/g)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Salinity
0 5 10 15 20 25 30 35
Tot
al P
art.
Se
(g
/g)
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Bivalve (C. amurensis) Concentrations
Year
1998 1999 2000 2001 2002 2003 2004 2005 2006
Cm
ss ( g
/g)
0
5
10
15
20
25ObservedIR = 0.45, AE = 0.2,0.45, 0.8IR = 0.65, AE = 0.2, 0.45, 0.8IR = 0.65, AE = 0.2, 0.45, 0.54IR = 0.85, AE = 0.2, 0.45, 0.80
White Sturgeon Concentrations
Year
80 85 90 95 00 05 10
Mu
scle
se
len
ium
co
nce
ntr
atio
n ( g
/g)
0
10
20
30
40
50
Suisun BaySan Pablo BayEstuary Mean
TTF = 1.7
Effect of Changing Boundary Conditions
Salinity
0 5 10 15 20 25 30 35
Pa
rtic
ula
te
Se
len
ium
( g
/g)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
ObservedLower BoundaryHigher Boundary
Scenarios Examined
Scenario Description1 Base case
2 Removal of all point source loads (refineries, POTWs), and local tributary loads
3 30% reduction in refinery and San Joaquin River loads, dissolved only
4 50% reduction in all point sources (refineries, POTWs), local tributaries and San Joaquin River loads, dissolved only
5 Increase dissolved selenium loads from San Joaquin River by a factor of 3, particulate loads remain the same as the base case
6 Decrease dissolved selenium loads from San Joaquin River by a factor of 50%, particulate loads remain the same as the base case
7 Increase particulate selenium loads associated with PSP, BEPS, and phytoplankton from Sacramento River by a factor of 3, dissolved loads remain the same as the base case
8 Decrease particulate selenium loads associated with PSP, BEPS, and phytoplankton from Sacramento River by a factor of 50%, dissolved loads remain the same as the base case
9 Increase San Joaquin River particulate loads by 3x, other loads stay the same
10 A natural load scenario, where the point sources are zero, the local tributary loads and speciation are at Sacramento River values, and the San Joaquin River is at 0.2 µg/l, at current speciation
Impact on Dissolved Se
High Flow Month (April, 1999)
0 1 2 3 4 5 6 7 8 9 10
Dis
solv
ed S
e (
g/l)
0.0
0.1
0.2
0.3
Low Flow Month (November, 1999)
0 1 2 3 4 5 6 7 8 9 10
Dis
solv
ed S
e (
g/l)
0.0
0.1
0.2
Dry Year Dry Month (July, 2001)
0 1 2 3 4 5 6 7 8 9 10
Dis
solv
ed.S
e (
g/l)
0.0
0.1
0.2
Impact on Particulate Se
High Flow Month (April, 1999)
0 1 2 3 4 5 6 7 8 9 10
Par
t. S
e (
g/g)
0.0
0.5
1.0
1.5
2.0
Low Flow Month (November, 1999)
0 1 2 3 4 5 6 7 8 9 10
Par
t. S
e (
g/g)
0.0
0.5
1.0
1.5
2.0
Dry Year Dry Month (July, 2001)
0 1 2 3 4 5 6 7 8 9 10
Par
t. S
e (
g/g)
0.0
0.5
1.0
1.5
2.0
Summary of Model Results The model is able to simulate key aspects of physical and biological
constituents that affect selenium concentrations. During calibration, the model was able to fit the patterns in concentrations of
dissolved and particulate selenate and selenite well, although it performed less well for the organic fractions. The model was also able to represent the observed variation in biota concentrations.
The model is a valuable tool to explore selenium transport, fate, and bioaccumulation in the bay, and can be applied in analyses in support of the TMDL, as demonstrated through a set of example scenarios.
A modeling study provides an opportunity to synthesize information from the system, and in doing so, highlights unknowns that may have a bearing on model predictions.
This report presents a set of data needs for further evaluation such as characterization of boundary conditions, selenium loads from major sources, recent water column concentrations and speciation, as well as biota concentrations.
Impact on Bivalve Se
High Flow Month (April, 1999)
0 1 2 3 4 5 6 7 8 9 10
Cm
ss S
e (
g/g)
0
5
10
15
20
25
30
35
Low Flow Month (November, 1999)
0 1 2 3 4 5 6 7 8 9 10
Cm
ss S
e (
g/g)
0
5
10
15
20
25
30
35
Dry Year Dry Month (July, 2001)
0 1 2 3 4 5 6 7 8 9 10
Cm
ss S
e (
g/g)
0
5
10
15
20
25
30
35