Application and Use of Passive Samplers for Monitoring ... · The Use of Passive Samplers to Monitor Organic Contaminants at Superfund Sediment Sites ... The Use of Passive Samplers

26 August 2013

The Use of Passive Samplers to Monitor Organic Contaminants at Superfund Sediment Sites

Application and Use of Passive Samplers

for Monitoring Organic Contaminants at

Superfund Sediment Sites

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Background

• Management of contaminated sediments includes source and institutional controls, remediation, and evaluating effectiveness of selected management actions

• Contaminant analyses for bulk or whole sediment often serve as a critical LOE used to support decision-making

− Often provide a poor predictor of exposure and subsequent risk since contaminant bioavailability is ignored

− EqP models were developed to predict freely dissolved concentrations in sediment porewater…BUT WITH LIMITATIONS

• Driven partly by cost of remedial decisions, these challenges have led to advances in use of passive sampling methods (PSMs)

– Goal: quantify bioavailability of contaminants in sediments

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Variety of PSM phases and configurations

Passive Sampling Phase or Media Configuration Target Analytes

Polydimethylsiloxane (PDMS) Coated fiber, vial HOCs

Polyethylene (PE) Film/sheet, tube HOCs

Polyoxymethylene (POM) Film/sheet HOCs

Ethylvinylacetate (EVA) Coated vial HOCs

Silicone rubber (SR) Sheet, Ring HOCs

Gels (e.g., DGT) Thin film “DGT” Metals

Resin impregnated polyacrylamide gel “Gellyfish” Metals

Metal-chelating media Disk/membrane Metals

Water-filled equilibration cell “Peeper” Metals

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Cfree estimates from PSMs

• Measure the equilibrated polymer concentration (Cp)

• Cfree = Cp / Kpw

where Kpw is the substance-specific polymer-water partition coefficient

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Regulatory “Acceptance” …

• They are accepted

• Are being used at several sites, mostly to revise the Conceptual

Site Model

• Is no formal Superfund acceptance process

• If passive samplers helps remedial project managers (RPMs)

answer key site questions, they will be used:

– Is there a risk, what are the key exposure pathways?

– What combination of dredging, capping, MNR?

– What are the risk-based goals and sediment cleanup levels?

– How to determine remedy effectiveness?

– Does the remedy meet performance targets and RAOs ?

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… So why aren’t PSMs more widely used?

• Key barriers to more regulatory acceptance and use include:

− Failure of practitioners and decision makers to understand the

advantages and limitations of these chemical-based approaches

over traditional analytical methods

− Confusion regarding the plethora of different methods and formats

that are increasingly reported in the literature

• Lack of consensus on:

− Technical guidance for PSM selection and standardization

− Use in regulatory decision-making contexts

• Limited experience in use and analysis of PSMs by commercial laboratories

• Uncertainty over cost vs. benefit

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Technical Guidance on Bioavailability & Bioaccessibility

Measurements Using Passive Sampling Methods

and Partitioning-Based Approaches for Management of Contaminated

Sediments

Summary of a SETAC Workshop

Rachel Adams

Ian Allan

Mayumi Allinson

Kim Anderson

Sabine Apitz

Chris Beegan

Todd Bridges

Steven Brown

Robert Burgess

John Cargill

Peter Campbell

Peter Chapman*

Yongju Choi

Beate Escher*

Will Gala

Jay Gan

Upal Ghosh*

Frank Gobas

Todd Gouin

Marc Greenberg*

Phillip Gschwend

Amanda Harwood

Steven Hawthorne

Paul Helm

Michiel Jonker

Susan Kane-Driscoll*

Peter Landrum*

Huizhen Li

Michael Lydy*

Keith Maruya*

Philipp Mayer*

Charles Menzie

Megan McCulloch

Julie Mondon

Munro Mortimer

Jochen Mueller

Amy Oen

Thomas Parkerton*

Willie Peijnenburg*

Danny Reible

James Shine

Foppe Smedes

Jing You

Gesine Witt

Eddy Zeng*

http://www.setac.org/resource/resmgr/publications_and_resources/executivesummarypassivesampl.pdf

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• Generally accepted that Cfree provides more relevant

exposure metric than total or bulk sediment conc

• Hydrophobic organic compounds (HOCs) – Significant literature available detailing calibration and application of PSMs in

sediment assessment (>100 papers)

– Estimates of Cfree from PSMs shown to better predict measurement

endpoints e.g. sediment bioaccumulation and toxicity

– Wide range of calibration parameters have been published for the various

polymers and/or configurations of PSMs

State of the Science

102 103 104 105 106

10

2

10

3

1

04

10

5 1

06

Ob

serv

ed

T

issu

e

(µg

/kg

lip

id)

Predicted Tissue = Cfree x Kow

in oligochaetes

PCBs & PAHs

0

20

40

60

80

100

0.001 0.01 0.1 1 10 100 1000

Toxic

> 41 TUS

urv

iva

l (%

)

Porewater PAH34 Conc. (Toxic Units)

Nontoxic

< 5.2 TU

Area of Uncertainty

Probit Analysis of EPA H. azteca 28-day Tests

Lu et al (2011) ET&C 30, 1109-16.

Adapted from Kreitinger et al., 2006; 2009

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Tissues & Integration of Passive Samplers Example: Naval Station San Diego

9

Good correlation between Musculista tissue and SPME-derived pore water concentrations for PAHs

Weak correlation between TOC-normalized bulk sediment concentration and tissue concentration

Benzo(b)fluoranthene, Benzo(k)fluoranthene, Benzo(a)pyrene

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R² = 0.8723

0

5

10

15

20

25

30

35

0.0 1.0 2.0 3.0 4.0

Tis

su

e C

on

cen

trati

on

(u

g/k

g)

Pore Water Concentration (ng/L)

PAH Tissue Correlation with Pore Water Concentration (0-7 cm)

R² = 0.2703

0

5

10

15

20

25

30

35

0 5000 10000 15000 20000 25000 30000

Tis

su

e C

on

cen

trati

on

(u

g/k

g)

Sediment Concentration (ng/g)

PAH Tissue Correlation with TOC Normalized Sediment Concentration

21 day PDMS Bulk sediments

Tissues & Integration of Passive Samplers Example: Naval Station San Diego

10

Good correlation between Musculista tissue and SPME-derived pore water concentrations for PAHs

Centrifugation slightly improved predictability over bulk sediments, but still disturbs samples and can confuse relationships between porewater and bioaccumulation

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R² = 0.8723

0

5

10

15

20

25

30

35

0.0 1.0 2.0 3.0 4.0

Tis

su

e C

on

cen

trati

on

(u

g/k

g)

Pore Water Concentration (ng/L)

PAH Tissue Correlation with Pore Water Concentration (0-7 cm)

21 day PDMS Centrifuged

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Potential Application in Laboratory & Field Settings

• Consensus that several PSMs ready for application

• Consider 5 key guiding principles for selection, preparation,

implementation and validation of PSMs

1. Define question(s) posed by managers to be addressed by measurement of Cfree

using PSMs

Endpoints addressed by PSMs

• Sediment toxicity

• Benthic organism bioaccumulation

• Transport (i.e., direction of flux,

gradients)

• Spatial extent delineation

• Site-specific KOC

• Model calibration / verification

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Guiding Principles (con’t)

2. Determine pros/cons of ex-situ (bring sediment

sample back to lab) versus in-situ application of

PSMs

Other Considerations • Site accessibility / security

• Time / Cost

• Level of expertise required

• Regulatory considerations

• Importance of spatial resolution

(heterogeneity; grab vs. fine scale)

• Temporal resolution

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3. Perform trade-off of key considerations to select the

most appropriate PSM(s)

Technical Considerations

• Target analytes (magnitude

of Kow, organic/inorganic)

• Physicochemical conditions

• Time for deployment

• Performance specs

(sensitivity, accuracy,

precision)

• Commercial availability

4. Establish QA/QC guidelines for project

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5. Quantify PSM measurement uncertainty and propagate

through the risk assessment

The uncertainty associated with Cfree measurements

using PSMs is expected to be only a fraction of the

uncertainty associated with the status quo

PSMs uses in sediment assessments and decision frameworks

• Nature and Extent

• Flux measurements

• Evaluating remedial options

• Exposure and risk assessment

• Use in tiered assessment approaches

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Fate, Transport and Exposure Processes

• Characterizing exposure under current

and future conditions

– Mass movement vs phase movement

– Getting from contaminant mass distribution to

exposure point concentrations and dose

– Projecting the effects of remedial actions

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Modeling

• PSDs are source of input parameters for

models:

– Contaminant mass-balance

– Sediment and contaminant transport

– Exposure and Dose-Response

– Bioaccumulation

– Engineering design

– Risk/site recovery projection

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Potential Risk Management Applications

• Cfree gives managers a

better predictor of

bioavailability for 3 key

exposure pathways:

1. Direct exposure to inverts.

(tox, bioaccum)

2. Flux from sediments to

overlying water column

3. Exposures in water

column

Sediment layer 1

Sediment layer 2

Water column

Contaminant

flux (CF)

CF

CFCF

CF

DDT

DDT DDT

DDT

DDT

DDT

Particulate

Phase

Dissolved

Phase

DDT

DDT

Measurements of Cfree with PSMs can reduce

uncertainty in risk assessment and subsequent

risk management decisions

1

2

3

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Applications of PSMs in Context of

Sediment Management

• Use in site investigations and risk assessment (these studies

form the technical basis of a clean-up decision)

– Pore water concentration estimates

– Moving toward use of PSM measurements as dose metric

– Indicator of bioaccumulation and/or bioavailability

• Use in remedial effectiveness monitoring

– Surface and pore water concentrations—bioavailability trends

– Sediment cap and amendment performance

– Surrogate for benthic organism bioaccumulation

– Indicator for fish bioaccumulation

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Example Profiles

-25

-20

-15

-10

-5

0

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Dep

th in

cap

(in

ches

)Pore water concentration(µg/L)

Pore water concentration profile(location 5)

Naphthalene

Fluorene

Acenaphthane

phenanthrene

Anthracene

Fluoranthene

pyrene

chrysene

B[a]A

B[b]F

B[k]F

B[a]P

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Site Year to Year Comparison

y = 1.2778xR² = 0.9413

0.001

0.01

0.1

1

10

100

1000

10000

0.01 0.1 1 10 100 1000

Co

nce

ntr

atio

n L

oca

ito

n 4

(2

01

0)

Concentration Location 4 (2009)

Site 1

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Site Year to Year Comparison

Site 1

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Summary of Potential Assessment & Risk

Management Applications

• Improvements from using passive samplers for Cfree

determinations and data collection—increase certainty:

– Ambient or compliance monitoring programs

– Quantifying spatial and temporal trends in bioavailable contaminants

– Identifying contaminant sources

– Dose metric to develop exposure concentration-response relationships

– Understanding of risk zones based on likelihood of effects

– Modeling (input parameters or verification data)

– Evaluating remedial options and designs

– Short- and long-term monitoring of chemical bioavailability

– Evaluating results of sediment treatment, disposal, or beneficial reuse

following management actions

– Evaluating remedy effectiveness

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Thank you for your

attention today

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Documents

Application and Use of Passive Samplers for Monitoring ... · The Use of Passive Samplers to Monitor Organic Contaminants at Superfund Sediment Sites ... The Use of Passive Samplers