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 (µg/g)

Uptake by bivalves

Uptake by predator species

ECoSModel

Results

DYMBAM

ModelTTF

SelenateDSe(VI)

SeleniteDSe(IV)

Organic

Selenide

DSe(-II)

Selenate +Selenite

PSe(IV+VI)

Elemental Se

PSe(0)

Organic Selenide

PSe(-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

Selenide

DSe(-II)

Selenate +Selenite

PSe(IV+VI)

Elemental Se

PSe(0)

Organic Selenide

PSe(-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 (µg/g)

Uptake by bivalves

Uptake by predator species

ECoSModel

Results

DYMBAM

ModelTTF

SelenateDSe(VI)

SeleniteDSe(IV)

Organic

Selenide

DSe(-II)

Selenate +Selenite

PSe(IV+VI)

Elemental Se

PSe(0)

Organic Selenide

PSe(-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

Selenide

DSe(-II)

Selenate +Selenite

PSe(IV+VI)

Elemental Se

PSe(0)

Organic Selenide

PSe(-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 concentrationsTTF = 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, dispersion

3. Phytoplankton (Chl a): result of advection, dispersion, growth, respiration, and grazing

4. 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

Selenate

Se(VI)

Organic

Selenide

Se(-II)

Selenite

Se(IV)

Dissolved SpeciesSelenate+ Selenite

Se(VI)+ Se(IV)

Organic

SelenideSe(-II)

Elemental Se

Se(0)

Selenate+ Selenite

Se(VI)+ Se(IV)

Organic

SelenideSe(-II)

Elemental Se

Se(0)

Organic Selenide

Se(-II)

PSP

Phyto-

plankton

BEPS

Mineralization, k1

Uptake

, k6

Mine

raliz

ation

, k 1

Minera

lization

, k1Ads/Des, a’, b

Ads/D

es, 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

CmsskeCfIRAECwkudt

dCmss ×−××+×=

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

leniu

m lo

ad

s (

kg/y

r)

0

2000

4000

6000

8000

10000

Riverine (kg/yr)

Refineries (kg/yr)

Tributaries (kg/yr)

Annual Selenium Loads

Dissolved Loads for Water Year

1999SJR @ Vernalis

2666

7%

Delta 365

South Bay

1607 176

SJR @ confluence POTWs

32% 3%

Sac. River @ Rio Vista Bay Exchange with Ocean Water

1502 5034

30%

Tributaries Refineries

820 559

16% 11%

Particulate Loads for Water

Year 1999SJR @ Vernalis

652

Delta

78 0

SJR @ confluence POTWs

11%

Sac. River @ Rio Vista Bay Exchange with Ocean Water

465 ~ 754 804 (32 BEPS)89%

Tributaries Refineries Bed Exchange

0 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

redic

ted

(p

su)

0

5

10

15

20

25

30

35

y = 0.9272 x + 1.0404

Jan 21, 1999

Sa

lin

ity (

psu

)

0

5

10

15

20

25

30

35

April 14, 1999

Sali

nit

y (

ps

u)

0

5

10

15

20

25

30

35

May 7, 1999

Sa

lin

ity (

ps

u)

0

5

10

15

20

25

30

35

June 7, 1999

Distance (km)

0 20 40 60 80 100

Sa

lin

ity (

ps

u)

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 (

µµ µµg

/L)

0

2

4

6

8

10

12

April 14, 1999

Ch

l a (

µµ µµg

/L)

0

2

4

6

8

10

12

May 7, 1999

Ch

l a (

µµ µµg

/L)

0

2

4

6

8

10

12

June 7, 1999

Salinity

0 5 10 15 20 25 30 35

Ch

l a (

µµ µµg

/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 35

0

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 (µg/L)

0 2 4 6 8 10 12 14 16

Pre

dic

ted

(µ

g/L

)

0

2

4

6

8

10

12

14

16

R2 = 0.358

Salinity

0 5 10 15 20 25 30 35

Sele

nite

(µg

/L)

0.00

0.02

0.04

0.06

0.08

0.10

Salinity

0 5 10 15 20 25 30 35

Sele

nate

(µ

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

nid

e (

µg/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

Part

. S

eIV

+S

eV

I ( µ

g/L

)

0.000

0.005

0.010

0.015

0.020

0.025

Salinity

0 5 10 15 20 25 30 35

Part

. S

e0

(µ

g/L

)

0.000

0.005

0.010

0.015

0.020

0.025

Salinity

0 5 10 15 20 25 30 35

Part

. S

e-I

I ( µ

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

Observed

Simulated

STN 6

Year

1998 2000 2002 2004 2006 2008 2010

TS

M (

mg

/l)

0

50

100

150

200

250

Observed

Simulated

STN 14

1998 2000 2002 2004 2006 2008 2010

TS

M (

mg

/l)

0

50

100

150

200

250

Observed

Simulated

STN 18

Year

1998 2000 2002 2004 2006 2008 2010

TS

M (

mg

/l)

0

50

100

150

200

250

Observed

Simulated

Evaluation of Chlorophyll a STN 3

1998 2000 2002 2004 2006 2008 2010

Ch

l a (

µµ µµg

/l)

0

2

4

6

8

10

12

14

16

18

20

Observed

Simulated

STN 6

Year

1998 2000 2002 2004 2006 2008 2010

Ch

l a (

µµ µµg

/l)

0

2

4

6

8

10

12

14

16

18

20

Observed

Simulated

STN 14

1998 2000 2002 2004 2006 2008 2010

Ch

l a (

µµ µµg

/l)

0

10

20

30

40

50

Observed

Simulated

STN 18

Year

1998 2000 2002 2004 2006 2008 2010

Ch

l a (

µµ µµg

/l)

0

2

4

6

8

10

12

14

16

18

20

Observed

Simulated

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

Pa

rt. S

eIV

+ S

eV

I ( µ

g/g

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Observed

Predicted

0 5 10 15 20 25 30 35

Part

. S

e0

(µ

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

Part

. S

eII (

µg

/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

To

tal P

art

. S

e (

µg

/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 (

µg

/g)

0

5

10

15

20

25Observed

IR = 0.45, AE = 0.2,0.45, 0.8

IR = 0.65, AE = 0.2, 0.45, 0.8

IR = 0.65, AE = 0.2, 0.45, 0.54

IR = 0.85, AE = 0.2, 0.45, 0.80

White Sturgeon Concentrations

Year

80 85 90 95 00 05 10

Muscle

se

len

ium

concen

tration (

µg/g

)

0

10

20

30

40

50

Suisun Bay

San Pablo Bay

Estuary 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

(µµ µµ

g/g

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Observed

Lower Boundary

Higher 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

so

lve

d S

e (

µg

/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

so

lve

d S

e (

µg

/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

so

lve

d.S

e (

µg

/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

Part

. S

e (

µg/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

Pa

rt.

Se (

µg/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

Part

. S

e (

µg/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 (

µg

/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 (

µg

/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 (

µg

/g)

0

5

10

15

20

25

30

35