1. Elizabeth River PCB TMDL Study: Numerical Modeling Approach
Jian Shen
Virginia Institute of Marine Science
College of William & Mary
May 11, 2011

2. Pollutant Sources from Watershed

3. PCB Transport in Estuary
Atmospheric
deposition
Air-sea
exchange
Runoff
Discharge
Sorbed to
POC & algae
PCB
Transport downstream
Sorption/desorption
Sorbed
to DOC
Dissolved
POC
Settling and
Resuspension
Transport
Upstream due to stratification
Ground
water
Diffusion
Burial

4. Modeling PCB concentrations in an Estuary
Use environmental computer model to simulate PCB transport in the estuary
Environmental computer models are mathematical representations of real-world conditions and are used to estimate environmental events and future changes.

5. James River Grid

6. Model Framework Hydrodynamic Eutrophication Model Model
Transport fields
mixing
Organic carbon in water column
Organic carbon in bottom sediment
point/nonpoint sources
Sorbent dynamics PCB model
(equilibrium partition)
Atmospheric deposition
Diffusion
PCB in bottom sediment
PCB in water
column
Deposition
re-suspension
Net burial

7. Hydrodynamic Model
Tide, Temperature, Salinity, TSS, Meteorological forcing (wind, atm. pressure, dry & wet temperature, cloud cover, solar radiation)
Surface elevation
Current
Dynamic
Model
Temperature
Salinity
Suspended sediment
Provide transport fields for eutrophication and PCB models

8. Sediment process model
Eutrophication Model
Point/Nonpoint source nutrients and carbon loads
Atmospheric deposition
(observation)
Model simulates:
Algae
Nutrients
Carbon DO
Flow
Tide
Temperature
Salinity
Wind
Suspended sediment
Water column
eutrophication model
Hydrodynamic Model
Deposition of organic matter
Organic carbon goes to PCB model
Sediment fluxes:
nutrients and SOD
Sediment process model

9. Eutrophication (Organic carbon) Model
Nutrients (N,P,Si)
Algae
Organic Carbon

10. PCB Model Atmosphere Point and nonpoint sources POC bound Dissolved
Gas Phase PCB
Air-water exchange
Particulate PCB
Deposition
Transport in/out
POC bound
Dissolved
PCB
DOC bound
PCB
Water column
Algae bound
Diffusion
Settling
Re-suspension
Dissolved
PCB
DOC bound
PCB
Surface
sediment
Sorbed PCB
Burial
Diffusion
Dissolved
PCB
DOC bound
PCB
Second
sediment layer
Sorbed PCB
Burial

11. Model Link Summary Hydro- dynamic Model Loading Loading Water column
Tide, Temperature, Salinity, TSS, Meteorological forcing (wind, atm. pressure, dry & wet temperature, cloud cover, solar radiation)
Surface elevation
Current
Hydro-
dynamic
Model
Temperature
Salinity
Suspended sediment
Loading
Loading
Water column
Particulate organic carbon
Water column
POC bound
Algae bound PCB
Dissolved PCB
Algal particulate organic carbon
Organic
Carbon
Model
PCB
Model
DOC bound PCB
Dissolved carbon
Added “organic” to “carbon model”, Added “Hydro-” to “Dynamic Model”
POC sorbed
PCB
DOC sorbed
PCB
Dissolved PCB
Particulate organic carbon
Dissolved carbon
Burial
Sediment
Sediment

12. PCB Model Sorption Processesv
v = PCB concentration on the solid / carbon (ng/g)
Cd =dissolved concentration (ng/L) Kd Cd
Equilibrium model assumes:
Algae
Particulate carbon
The relationships between total PCB, dissolved PCB, particulate carbon bound PCB, algal bound PCB, and dissolved carbon bound PCB are:
PCB
Dissolved PCB
Dissolved carbon
fx = fraction of each component
C = total PCB

14. PCB Transport Model Equation
Settling
Diffusion
Where H is water depth, C is total PCB concentration, Ab is eddy diffusivity, and wsi (i=1,2) are settling velocities associated with particulate organic carbon and algal organic carbon,  is decay constant, u, v, w are velocity at x-, y-, and z- directions, mx and my are scale factors of the horizontal coordinates.

15. The boundary condition at the water column sediment interface, z = 0, is:
Where are POC and algal carbon fluxes between sediment bed, and water column (mass per unit area per second), defined as positive from the bed,  and s are porosities in water column and sediment. The subscripts ‘w’ and ‘s’ denote water column and sediment, respectively, and qdif is diffusion velocity.
The volatilization which occurs at the surface depends on the mass transfer coefficient at the air-water interface and the concentration of PCB in the water column. The boundary condition at the water column and air interface, z = 1, is: (Bamford, et al., 2002)
Where Kv is the volatilization mass transfer coefficient (L/T), Z is the thickness of the first layer near the surface, Ca is the vapor phase PCB concentration in air (M/L3) and KH is the dimensionless, temperature-corrected Henry’s law constant.

16. Bottom Sediment Model Equation
Lost due to re-suspension
Settling from water column
Settling to deep sediment layer
Water column
Diffusion between water column and sediment
Surface layer
Second layer
Where B is the thickness of the sediment layer.

17. Data Needed for Hydrodynamic Model Calibration
Tide
use NOAA observation data at Sewells Point
Salinity at open boundary
use the Chesapeake Bay model output (available from )
Flow data
use USGS upstream daily flow (Appomattox River USGS and Richmond station USGS37500)
Meteorological forcing data
use NOAA data at Sewells and Gloucester Point
wind, atmospheric pressure
dry & wet temperature
cloud cover and solar radiation

18. Link James River Model to the Bay Model
Water quality stations for carbon model calibration
Changed “like” to “link”
Output salinity will be used for James River model boundary condition at the mouth
Sewells Point

19. Data Needed for Eutrophication Model Calibration
Point source loading
Chesapeake Bay program/DEQ
James River mouth open boundary
Monthly observations
Nonpoint source loading
Chesapeake Bay Phase V watershed model output,
Flow
Nitrogen
Phosphorus
Carbon
Algae

20. Data Needed for PCB Model Calibration
Bottom sediment PCB data
use for initial sediment condition (sediment study)
Upstream PCB data
estimate upstream PCB inflow
Loading from contaminated sides
Storm water data ?
Point source data ?
Nonpoint source loading (background, unknown loadings)
estimate based on event driven concentration and flow
Atmospheric deposition
Historical observations/new observations
Model calibration data
Collect short-term data covering large area
Intensive survey data
monthly or bimonthly PCB data for a year at 2-3 stations (i.e., 2-JMS074.44, 2-ELI04.79 )

21. Swapped out map to show both stations

22. Next Steps… Data collection Nonpoint source estimation
Pollutant source estimation
Model setup
Hydrodynamic model calibration
Eutrophication model calibration
PCB Model calibration procedure

23. Questions / Discussion
DEQ PCB TMDL website:
Contacts:
Mark Richards Jennifer Howell
Central Office DEQ Tidewater Regional Office, DEQ
(804) (757)