Collaborative Meeting on Modeling Mercury in Collaborative Meeting on Modeling Mercury in Freshwater EnvironmentsFreshwater Environments

January 19, 2006January 19, 2006Niagara Falls, NY Niagara Falls, NY

Overview of Watershed and Water Body Models for Mercury

used by the US EPA

Christopher KnightesChristopher KnightesUSEPA / ORD / NERL / ERD Athens, GAUSEPA / ORD / NERL / ERD Athens, GA

Wet Deposition

Hg2+

Dry DepositionHg2+(p,v)

Evasion (Hg0)

Resuspension

Runoff and Erosion

Litterfall and

Throughfall

Hg0

WatershedProcesses

Settling

Hg2+

MeHg

Diffusion

DryDeposition

Burial

Mercury in WatershedsAnd Water Bodies

Food WebTransformation

Ground Water?

MeHgHg2+

Primary1 and Support Models for Analysis of Mercury Fate

available from EPA - Athens

• SERAFM – Mercury Risk Screening Model

• WCS (MLM) – Watershed Loading Model

• GBMM – Grid-Based Watershed Loading Model

• WhAEM2000 – Groundwater Flow Model

• WASP7 – Water Body Pollutant Fate Model

• EFDC – Water Body Hydrodynamic Model

• BASS – Aquatic Food Web Model1 Simulates mercury explicitly.

Watershed Mercury Models

• Watershed Characterization System, Mercury Loading Module – WCS MLM Current available model Grid soil calculations, sub-watershed loading resolution Simple hydrology, erosion, mass balance Provides yearly-average concentrations, loads

• Grid-Based Mercury Model – GBMM Projected Availability: January 2006 Fine grid resolution Simple wetland and tributary transport and transformation

algorithms for mercury Provides daily concentrations, loads Future incorporation into BASINS toolkit

Water Body Mercury Models• SERAFM:

Process-based, Steady-State Lake/Pond Model Enhanced version of IEM-2M from Mercury Report to Congress Stand-Alone model developed for Risk Assessors Incorporates Watershed Runoff and Erosion, Mercury Cycle Chemistry,

Bioaccumulation, and Wildlife/Human Risk Values Provides yearly-average concentrations, loads Serves as a Repository for Updates in Mercury Science and Modeling

• WASP7 and WASP7 Mercury Module: Dynamic, Process Modeling Framework General design for modeling contaminant fate and transport in surface

waters Compartment Modeling Approach, Lakes/Ponds/Rivers Incorporates Mercury Module Is being updated to incorporate SERAFM Science Model architecture is being updated and improved

PamlicoSound

TrentRiver

ClubfootCreek

AdamsCreek South

River

E

Scale

10 km0

N

S

W

5 km

BeardCreek

SlocumCreek

HancockCreek

UpperBroadCreek Goose

Creek

SwiftCreek

BroadCreek

GreensCreek

DawsonCreek

BachelorCreek

WASP Mercury Module

VolatileExchangeof Hg(0)

Watershed and Atmospheric Loadsof Hg(II) and MeHg

State VariablesHg(0) SiltHg(II) SandMeHg Biotic SolidsMethylation

Demethylation Oxidation

Reduction

Burial

Point Source Loads of

Hg(II)

DOC

Mercury Watershed/Water Body Links

Watershed ModelsWCS-MLM

GBMM WARMF

Water Body ModelsWASP

SERAFM

Hydrodynamic ModelsEFDC

DYNHYDEPD-RIV1

BioaccumulationModelsBASSFCM-2

External Spreadsheets

ASCII FilesWindows Clipboard

Atmospheric Models

Brier Creek Mercury Modeling: WCS-MLM and WASP7

HgII in Soil

Tributaries

reduction,evasion

Atmospheric Wet and Dry Deposition

reduction,volatilization

Impervious Surface

volatilization

export

export

Water Surface

runoff

export

runoff and erosion

sediment layer

MeHg Hg(II) Hg0

Silt, POM water column Sand

Burial

Leaching

Mercury Reduction Benefits Analysis:Changes in Mercury Concentrations and

Evaluation of Response Times for Mercury Emission/Deposition Reductions

Applications of

SERAFM, WASP, WCS, and BASS

Eagle Butte, South Dakota Pawtuckaway Lake, New Hampshire

Lake Waccamaw, North Carolina Brier Creek, Georgia Lake Barco, Florida

Summary of Ecosystem CharacteristicsParameter Pawtuckaway

Lake, NHLake

Waccamaw, NCLake Barco,

FLEagle

Butte, SDBrier

Creek, GA

Watershed Area

50 km2 217 km2 0 4.2 km2 2,190 km2

Lake Area 3.64 km2 34.7 km2 0.12 km2 0.19 km2 n/a

Watershed/

Lake Ratio

13.7 6.3 0 22 n/a

Residence Time

165 days 241 days 0 0 12 days

Stratification Yes No No No No

Depth 5m 2.3m 3.7m 2.0m 0.3 – 2.0 m

pH Neutral Acidic Acidic Alkaline n/a

Trophic State Dystrophic Mesotrophic Oligotrophic Eutrophic n/a

Total Hg Dep 20.7 ug/m2/yr

29.2 ug/m2/yr

31.5 ug/m2/yr

19.8 ug/m2/yr

26.8 ug/m2/yr

Predicted vs Observed Fish Concentrations

2

2.5

3

3.5

2 2.5 3 3.5

Log Hg fish (ng/g) - Observed

Lo

g H

g f

ish

(n

g/g

) -

Pre

dic

ted

PawtuckawayLake

Lake Waccamaw

Lake Barco

Eagle Butte

Observed vs. predicted fish mercury concentrations in model ecosystems at steady state with no change in atmospheric loading. Straight line represents 1:1 relationship between observed and modeled results.

Fast: 1 cm sediment, D = 10-4 cm2/s

Medium: 2 cm sediment, D = 10-4 cm2/s

Slow: 3 cm sediment,

D = 5x10-5 cm2/s

Lake Barco, FL50% Loading Reduction

MMapsProportional Relationship

Representative Changes in Fish Concentrations in Response to

Emission/Deposition Reductions

Fast: 1 cm sediment, D = 10-4 cm2/s

Medium:2 cm sediment, D = 10-4 cm2/s

Slow: 3 cm sediment,

D = 5x10-5 cm2/s

Pawtuckaway Lake, NH50% Loading Reduction

MMapsProportional Relationship

Site SERAFM WASPFast Medium Slow Fast Medium Slow

Eagle Butte, SD 3 4 6 6 11 16

Pawtuckaway Lake, NH 80 125 >180 24 44 69

Lake Waccamaw, NC 3 6 12 10 15 17

Brier Creek, GA n/a n/a n/a 49 82 123

Lake Barco, FL 14 28 45 n/a n/a n/a

Sensitivity Range of Response Times

Current and Historical Applications by NERL-ERD Staff

• Steamboat Creek and Wetland Mesocosm near Reno, NV Scott Brown (MS Thesis at UNR) under advisement of Chris Knightes (SERAFM)

• Sudbury River, MA Chris Knightes (SERAFM, WASP7)

• Cheyenne Sioux Reservation Ponds, SD John Johnston (SERAFM)

• Five Representative Ecosystems: Brier Creek, GA; Lee Dam, SD; Pawtuckaway Lake, NH; Lake Barco, FL; Lake Waccamaw, NC. Robert Ambrose, Elsie Sunderland, Chris Knightes, John Johnston (WCS-MLM,

SERAFM, WASP7, BASS)• Vermont & New Hampshire Lakes

Chris Knightes (R-MCM)• Ogeechee, Canoochee, & Brier Creek River Basins, GA

Tim Wool, Chris Knightes & Robert Ambrose (WCS-MLM, WASP7)• Ochlockonee, Savannah, St. Mary’s, Satilla, Suwanee, GA

Tim Wool & Robert Ambrose (WCS-MLM, WASP7); Craig Barber (BASS)• Everglades, FL

Robert Ambrose, Craig Barber, Rochelle Araujo (WASP5, BASS)