impact of groundwater discharge on contaminant behavior in

1

Office of Research and Development, National Risk M anagement Research Laboratory1 Land Remediation and Pollution Control Division, Cincinnati, OH2 Ground Water and Ecosystems Restoration Division, Ada, OK 3 formerly with USEPA/ORD

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Robert Ford1, Kirk Scheckel1, Steven Acree2, Rick Wilkin2, Randall Ross2, Bob Lien1, Patrick Clark1, Frank Beck3, Todd Luxton1, Cindy Paul2, Aaron Williams3 and Brad Scroggins3

Region 1Industri-Plex - Joseph LeMayFort Devens - Ginny Lombardo, Bill Brandon, Rick Sugatt

Impact of Groundwater Discharge on Contaminant Behavior in Sediments

23 Oct 2008NSF

1

Conceptual Model Conceptual Model GW/SW Transition ZoneGW/SW Transition Zone

EPA-540-R-06-072 Evaluating Ground-Water/Surface-Water Transition Zones in Ecological Risk Assessmentshttp://www.epa.gov/oswer/riskassessment/ecoup/pdf/eco_update_08.pdf

EPA/600/S05/002 The Impact of Ground-Water/Surface-Water Interactions on Contaminant Transport with Application to an Arsenic Contaminated Sitehttp://www.epa.gov/ada/download/briefs/epa_600_s05_002.pdf

NARPM 2008 - Ground Water/Surface Water Interaction - Concepts, Field Methods, and Site Management Challenges Panel Session http://www.ttemidev.com/narpm2008Admin/conference/agenda.cfm

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2

Categories of GW InfluenceCategories of GW Influence

1) Direct contribution of contaminant mass from discharge of the plume through sediments

2) Indirect influence on contaminant speciation due to biogeochemical processes that control sediment properties (precipitation-dissolution)

3) Indirect influence on contaminant speciation or mass due to the influence of groundwater discharge on microbial processes that support contaminant transformation or degradation.

3

Conceptual Model Conceptual Model -- RevisitedRevisited

GW/SW Transition ZoneEPA/600/S-05/002

Surface Water (SW)O2 Diffusion

Contaminated SedimentChlorobenzene & Arsenic

Competing processes influenced by GW discharge:

1) Chlorobenzene oxidation / SO42-

reduction2) Fe2+ oxidation by O2(g) / H3AsO3

coprecipitation with Fe(OH)3(s)3) SO4

2- reduction / H3AsO3coprecipitation with FeS(s)

Groundwater (GW)Fe2+, SO4

2-, H3AsO3

3

4

Potential Influence on RemedyPotential Influence on Remedy

�Physical Barrier• Discharge causing physical damage

�Reactive Barrier• Discharge causing short-circuiting• Flux of non-contaminant constituents

consume reaction capacity

�Monitored Natural Recovery• Changes in flux of constituents

influence extent or direction of attenuation process (biodegradation or immobilization)

• Changes in GW flux could cause contaminant transport via advection

5

IndustriIndustri --Plex Superfund SitePlex Superfund SiteControls on Sediment ChemistryControls on Sediment Chemistry

Degree-of-sulfidation

0.8 - 1.00.4 - 0.80 - 0.4

DOS>0.5

DOS>0.2

DOS>0.8

Ground-waterinput

25 m Hall’s BrookHolding Area

HClpyr

pyrAVS

FeFe

FeFeDOS

++

=

ArsenicPlume Hydrocarbon

Plume

4

6

IndustriIndustri --Plex Superfund SitePlex Superfund Site

O2

Fe(II)aq

FeS(s)

Fe(OH)3(s)

Aqu

eous

Sol

id

SO4(aq)

Surface Water

Groundwater

Flow path for geochemical

measurements

H3AsO3(aq)

SolidPhase

As

GW/SW Transition Zone

Sulfate Reducing

IronReducing

B

Upgradient -anaerobic hide piles & wetland soils

IronOxidizing

O2

Fe(II)aq

FeS(s)

Fe(OH)3(s)

Aqu

eous

Sol

id

SO4(aq)

Surface Water

Groundwater

Flow path for geochemical

measurements

H3AsO3(aq)

SolidPhase

As

GW/SW Transition Zone

Sulfate Reducing

IronReducing

B

Upgradient -anaerobic hide piles & wetland soils

IronOxidizing

• Sediment chemistry unique at intersection of GW plumes discharging into pond

• Sediments serve as an “incubator” for microbial processes and contaminant transformations

• SW conditions impacted by biogeochemical processes within shallow sediments

7

1

2

3A

3B

4

Fe oxidation-precipitation

Iron (hydr)oxide settling

Iron (hydr)oxide dissolution

Deposition & diagenesis

Dissolved Fe & As transport

Bound to oxygen

Bound to sulfur

Arsenic is most labileArsenic is most labile

IndustriIndustri --Plex Superfund SitePlex Superfund SiteFate of Metals entering Pond SystemFate of Metals entering Pond System

5

8

Fort Devens Fort Devens -- Project ObjectiveProject Objective

�Project Goals– Identification of the mobile form of arsenic in

groundwater– Identification of the process(es) controlling arsenic

uptake onto Red Cove Study Area sediments– Evaluation of the stability of arsenic associated with

Red Cove Study Area sediments

�Site Characterization– GW hydrology and chemistry in Red Cove Study Area– Sediment chemistry including arsenic speciation in

Red Cove– SW chemistry in Red Cove

�Provide recommendations for GW & sediment remedies, where applicable

9

Site CharacterizationSite CharacterizationMonitoring NetworkMonitoring Network

Shepley’sHill Landfill

PlowShopPond

Red CoveRed CoveStudy AreaStudy Area

6

10

Site Characterization: Site Characterization: PhysicalPhysical

Mapping Sediment Temperature

Measuring GW Flow Potential

Measuring GW Discharge

Red Cove

11

PZ Flow PotentialUpNegligibleDown

GW wells

PZ11

PZ9

PZ8

PZ6

PZ5

GW Flow Potential – Head Difference (ft)

9/11/07 11/6/07 5/1/08 8/20/08 9/17/08

PZ11 0.04 -0.26 NM -0.10 -0.08

PZ9 0.04 0.02 0.05 0.03 0.03

PZ8 0.00 0.03 0.02 0.02 0.01

PZ5 0.05 0.08 0.13 0.11 0.10

PZ6 0.11 0.14 NM NM 0.17


7

12


Direct measurement of GW discharge into Red Cove

+2.56 Jun 08

+2.77 Apr 07

+1.13 Jun 08

+2.83 Apr 07

+2.77 Apr 07+1.95 Aug 07+1.12 Nov 07

+2.44 Apr 07

+0.30 Jun 08

+0.15 Jun 08

Nor

thin

g

Easting

+0.86 Jun 08-0.68 Aug 08

Current locations of automated advective flux meters(Bob Lien, ORD-Cincinnati)

Seepage Rate(cm/day)

Region in aquifer where change in flow gradient begins; transition from discharge to recharge.

13


5/30/2008 6/30/2008 7/30/2008 8/30/2008 9/30/200850

60

70

80

50

60

70

80

50

60

70

80

50

60

70

80

Tem

pera

ture

(F

)

Date

PZ13 PZ14

2 ft below sediment

1 ft below sediment

sediment surface

3 ft above sediment

Sediment temperature cooler at location of highest GW discharge.

PZ13

Nor

thin

g (m

)

Easting (m)

Cove Perimeter Advective Flux Meter Surface Water Piezometer

PZ14

8

14

Site Characterization: Site Characterization: PhysicalPhysicalSignature for Influence of GW Discharge on Signature for Influence of GW Discharge on Sediment TemperatureSediment Temperature

192180 192200 192220 192240

922640

922660

922680

922700

922720

7 8

9

10

9

192180 192200 192220 192240

922640

922660

922680

922700

922720

RSK 37-42

RSK 13-15

RSK 8-12

RSK 1-7

SW

Temp Buttons

Easting (meters)

Nor

thin

g (m

eter

s)

50

52

54

55

57

59

61

62

64

GW

RSK 16-20

49.4 ± 0.4 F

52.5 ± 0.2 F

50.5 ± 0.2 F

52.0 ± 0.4 F

SW (64.5-69.6 F) RSK RCTW

K (mg/L) Aug 21-23, 2007 Aug 22, 2007

Relative Influence

• Sediment temperature at 1 foot depth measured continuously at “Temp Buttons” locations

• Cooler temperatures indicative of GW influence; warmer indicates less GW influence

• Distribution of cooler temperatures generally aligns with distribution of high K in shallow GW (5-10 ft below sediment)

15

Site Characterization: Site Characterization: ChemistryChemistryUpgradientUpgradient GW GW –– RC GW RC GW –– RC SWRC SW

• Chloride (Cl) & sodium (Na) are not a reliable indicators of GW discharge• Potassium in shallow SW relatively constant & low, providing a signature

for SW influence in deep SW and sediment pore water

0 10 20 30 40

0

10

20

30

40

50

0 5 10 15 20 25

0

10

20

30

40

50

SW02A 4/07

SW02B 4/07

SW02B 8/07, SW04 9/07, SW05 9/07

SW03 8/07

IC 5/06

MC 5/06

K RangeRSK 1-7

RSK 16-20RSK 8-12

Na RangeRSK 1-7

RSK 16-20RSK 8-12

RSK Linear Trend RCTW GW Wells Shallow SW 2006-2007 RSK GW Wells

Cl (

mg/

L)

Na (mg/L)

Cl RangeRSK 1-7

RSK 16-20RSK 8-12

K (mg/L)RC = Red Cove

9

16

Highest As in upgradient GW wells associated with high K

0 2 4 6 8 10 12 14

0

100

200

300

400

500

600

700

800

900

As

(µg/

L, <

0.45

µm

)

K (mg/L, <0.45 µm)

RSK GW (average) Shallow SW

RSK 37-42

RSK 16-20

RSK 13-15

RSK 8-12

RSK 1-7

Site Characterization: Site Characterization: ChemistryChemistryAs in As in UUpgradientpgradient GW GW –– Shallow SWShallow SW

17

192190192200

192210192220

192230192240

192250

9.39.7

8.4

13.411.3

2.5

10.7

6.1

12.4

10.5

2.2

8.8

4.3

2.4

2.4

7.1

10.1

9.3

11.8

5.8

10.2

11.3

192190192200

192210192220

192230192240

192250922650

922660

922670

922680

922690

922700

922710 K (mg/L)August 2007

Easting (meters)

Nor

thin

g (m

eter

s)

9.8±0.7

RCTW Deep SW Cove Perimeter

Easting (meters)

0

2

4

6

8

10

12

14

5.4

K (mg/L)August 2006

Deep SW similar to shallow GW in RCTW wells at known discharge location

Site Characterization: Site Characterization: ChemistryChemistryPotassium SignaturesPotassium Signatures

10

18

20003000

1000

4000

1000

7 8

9

10

9

192180 192200 192220 192240 192260

922640

922650

922660

922670

922680

922690

922700

922710

922720

0.3 ± 0.3

3.8 ± 2.6

Sediment RCTW As Flux (g/dy) Cove Perimeter

Easting (meters)

Nor

thin

g (m

eter

s)

0

1000

2000

3000

4000

5000

6000

7000

8000

6800

8600

25.5 ± 14.3

14.9 ± 12.5

RSK 1-7

RSK 16-20

RSK 8-12

RSK 13-15

RSK 37-42

8.0 ± 7.7

K (mg/L)

As (mg/kg)

6940

Site Characterization: Site Characterization: ChemistryChemistryGW As Flux and Sediment As ContentGW As Flux and Sediment As Content

19

• High particulate Fe in SW from GW discharge of Fe2+

• Oxidation & precipitation of Fe2+ captures As, but only after contact with DO in SW

SuspendedSolids

(next slide)

-200 0

200

400

600

800

5

4

3

2

1

0

0 2 4 6 8

55 60 65 70

0 30 60 90 120 150 180

0 200 400 600 800 0 10 20 30

5

4

3

2

1

0

Aquifer

Water Surface

SedimentSurfaceD

epth

(ft

bws)

Sp. Cnd. (µS/cm) ORP (mV)

RCTW4

pH (S.U.) DO (mg/L)

Temp (F)

Turb. (NTU)

SW02B20 Aug 2007

AcuteAWQC

Chr

onic

AW

QC

Part. As (µg/L) Diss. As (µg/L)

MC

L

Diss. K (mg/L) Fe2+ (mg/L) Part. Fe (mg/L)

GW sampled using low-flow procedure, i.e., low turbidity

Site Characterization: Site Characterization: ChemistryChemistryCrossCross --section through Red Covesection through Red Cove

11

20

Red Cove Surface WaterRed Cove Surface WaterSuspended Solids CompositionSuspended Solids Composition

• Seepage meter installed adjacent to location SW02B (suspended solids)

• Orangish-red precipitates in SW are the mineral ferrihydrite

• Zones of high Fe precipitation tend to have low aquatic plant growth

SeepageMeter atSW02B

21

0 5 10 15 20 25 30 35 40

0

2000

4000

6000

8000

10000

Linear Reg (All, R2=0.91)

Linear Reg (Shallow, R2=0.94) RC Sediment (All) RC Sediment (Shallow) RC Susp. Solids (SW02B)

Aci

d E

xtra

ctab

le A

s (m

g/kg

)

Acid Extractable Fe (wt%)

Red Cove Surface WaterRed Cove Surface WaterRelationship between Suspended Relationship between Suspended Solids & Shallow SedimentsSolids & Shallow Sediments

• Significant correlation between Fe and As in sediments• Concentration of As in suspended solids from Fe precipitation

consistent with most elevated concentrations in shallow sediments

Suspended solids from SW02B

12

22

Red Cove SedimentsRed Cove Sediments• Spatial heterogeneity in Fe and S distribution in sediment• S generally higher near location of plume discharge• Fe generally higher further out in cove where more oxidizing

0.2

0.40.6

0.8

1.01.21.4

0.7

0.4

0.0

0.71.9

3.3

0.2

1.1

1.1

0.3

192190 192200 192210 192220 192230 192240 192250

922660

922670

922680

922690

922700

922710

0.1

Sediment S (wt%)

Sediment Surface Water RCTW Cove Perimeter

Easting (meters)

Nor

thin

g (m

eter

s)

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.3

10 15

20 25

5

30

10

14.4

3.9

5.0

3.06.115.6

8.8

23.4

23.0

37.4

192190 192200 192210 192220 192230 192240 192250

922660

922670

922680

922690

922700

922710

1.5

Sediment Surface Water RCTW Cove Perimeter

Easting (meters)N

orth

ing

(met

ers)

0

5

10

15

20

25

30

35

40Sediment Fe (wt%)

35.9

Highest sulfate flux

23

Red Cove SedimentsRed Cove Sediments

• Sediment As associated with Fe-bearing minerals (mostly Fe oxides)• Predominantly As(III) in western & central transect; As(V) more significant

in eastern transect• High As concentrations and greater As(V) in eastern transect due to less

GW discharge and more oxidizing condition (ferrihydrite more stable)

13

24

192215 192220 192225 192230 192235

208

210

212

214

216

218 MC SW02B SW04

RCTW 4RCTW 9

RCTW 10

Easting (meters)

Ele

vatio

n (f

t AM

SL)

ContaminatedSediment

Conceptual Site ModelConceptual Site ModelRed Cove ArsenicRed Cove Arsenic

Contaminated GW discharge introduces high As & Fe into Red Cove

Fe-oxide rich shallow sediment layer produced from Fe2+

precipitation & settling, but As-laden material is not stable due to reducing conditions

Direct Recycled

25

0 2 4 6 8 10 12 14

0

200

400

600

800

1000

SW02A SW02B1

SW02B2

SW03SW04

SW05

IC

MCRCTW6

RCTW8

RCTW6

Acute AWQC

Chronic AWQC

Deep SW 2006-2007 Shallow SW 2006-2007 RCTW 2006 RCTW 2007

As

(µg/

L)

K (mg/L)

MCL

Surface Water Arsenic Surface Water Arsenic Concentrations within Red CoveConcentrations within Red Cove

• SW02 & MC in known GW discharge area

• SW03 & SW04 in areas with less significant GW discharge (based on sediment temperature measurements)

• Existing contaminated sediments contribute As to overlying SW

14

26

Fort Devens Fort Devens -- Existing Data GapsExisting Data Gaps

1) Improved delineation of As plume discharging into Red Cove• Acquisition of additional GW chemistry data to delineate As

distribution throughout saturated overburden thickness in central portion of Shepley’s Hill Landfill

• Better targeting for potential remedy to increase efficiency and reduce cost

2) Exposure assessment within cove to characterize risk• Differentiate influence of direct GW discharge vs. sediment

exposure (currently in development)

3) Acquisition of additional depth-resolved SW data to more completely map out the spatial distribution of redox conditions and dissolved contaminants within the water column

27

� USEPA Region 1 – Ginny Lombardo (RPM), Bill Brandon, Rick Sugatt

� Dept of the Army – Robert Simeone; ECC – David Reault

� USEPA Region 1 Laboratory – Dan Granz, Tim Bridges

� Gannett-Fleming, Inc. – Carol Stein, David McTigue� Shaw Environmental, Inc. (Analytical Support under

Contract 68-C-03-097)� USEPA/ORD – Thomas Holdsworth, Dennis

Timberlake, Thabet Tolaymat

AcknowledgementsAcknowledgements

impact of groundwater discharge on contaminant behavior in

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