sanborn head has met the standards and requirements of the

“Sanborn Head has met the standards and requirements of the

Registered Continuing Education Program. Credit earned on

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COPYRIGHT MATERIALS

This educational activity is protected by U.S. and International copyright laws. Reproduction, distribution, display and use of the educational

activity without written permission of the presenter is prohibited.

©Sanborn, Head & Associates, Inc., 2020

Purpose and Learning Objectives

Participants will gain a better understanding of PFAS fate & transport, including air deposition transport, fate in saturated soil, and fate in groundwater. This course will discuss the complexities of PFAS fate and transport including considerations when investigating a site for PFAS contamination. This course will also review current technologies being used for PFAS treatment and remediation as well as experimental technologies and approaches currently in the research phase.

At the end of this presentation, you will be able to:1. Describe various sources of PFAS contamination.2. Explain variations in PFAS fate & transport as compared to better-studied

contaminants of concern.3. Explain the fate & transport considerations that should be part of PFAS

investigations.4. Describe ways in which PFAS-impacted media can be treated or

remedied.

PFAS Updates: PFAS Fate & Transport Characteristics and Remediation Alternatives

Stephen Zemba, Ph.D., P.E.Harrison Roakes, P.E.

PresentationOverview

PFAS Background/Introduction Atmospheric Deposition Fate and Transport Models Emissions Deposition to soil Soil as a source to groundwater

2

PFAS– AClassofChemicals

Fluorocarbon tail Strong bonds Hydrophobic Lipophobic Varying length Branched isomers

Functional group Strong to weak

acids Hydrophilic Effects chemical

properties

O

OH

F F F F F F FF

F F F FFF Fperfluorooctanoic acid

(PFOA)

Variations Chain length Fluorine saturation Precursors

Source: DraftToxicologicalProfileforPerfluoroalkyls, U.S. Department of Health and Human Services, 2018

> 4,700 identified ~ 30 quantified Focus on PFOA and PFOS

(8 C compounds)

ImportanceofDrinkingWaterExposureAverage PFOA Levels in Blood (µg/L)

PFOS: National average 4.3 µg/l Belmont, MI individual 3200 µg/l

https://www.health.ny.gov/environmental/investigations/hoosick/docs/qandabloodtestingshort.pdf

5

LifespanExposureofPFOAbasedonTransgenerationalToxicokineticModelforPFASCompounds

Goeden et al. (2018), J Expo Sci Environ Epidemiol. 29(2):183-195.

20.6 µg/L PFOAat 1 year

6.6 µg/L PFOAat 7 years

3.6 µg/L PFOAsteady state as adult

4.0 µg/L PFOAat time of delivery

3.6 µg/L PFOAsteady state as adult

4.0 µg/L PFOAat time of delivery

1.1 µg/L PFOAat one year

breastfeeding

Goeden etal. model used in MN and NH toestablish drinking water standards

Based on maximum target PFAS serum level Example for NH PFOA MCL of 12 ng/l

PFOSSurfaceWaterScreeningLevels

State

DrinkingWater

Std/Guideline(ng/l)

SurfaceWaterScreeningLevel

(ng/l)

MI 16 11

MN 15

6(lakes)

14(rivers)

FL 70 4(proposed)

Image courtesy of usda.gov

AtmosphericDepositionofContaminants

Wet and DryDeposition

Courtesy of NH Department of Environmental Services

DepositionFactors/Considerations

Particles and vapors Dry v.Wet Dry “Donut Hole”

8

PlumeImpaction

Drinking water wells up to ~20 miles from industrial source werecontaminated with PFOA through air deposition (WV & Ohio).

Source: S. Frisbee,West Virginia Univ.School of Medicine. 2008.

Courtesy of Gloria B. Post, NJDEP, June 5, 2013

PFASInvestigationNearManufacturingPlant

Industrial Source

*Detected in public water supply wells at up to 280 ng/L.

0 1 32Miles

*Public

610 ng/l

Industrial Site

Courtesy of Gloria B. Post, NJDEP, June 5, 2013

PFASAirborneTransportFoundNearNJFacility

PFOA– AirborneDepositionSite

Courtesy of NH Department of Environmental Services

Merrimack, NH – textilecoating operation

Most points representindividual monitoring wells

NH PFOA MCL (underchallenge) set at 12 ppt

Some impacts likely fromwater discharges at factoryand local landfill

Commingled impacts nearairport?

FormerFactory

RiverFlow

Elevated Terrain

Waste Disposal Area

Airport

EvidenceofGenX DepositioninNC

12

AtmosphericDepositionfromAqueousFireFightingFoamhttp://www.miljodirektoratet.no/old/klif/publikasjoner/2444/ta2444.pdf

13

Mongstad Oil Refinery – Norway’s largest (230,000 bbl/d) Fire training initiated in 1988 Peak levels >10,000 ppb in soil found 52 m from source Pattern in soil suggests spray drift and deposition

Disclaimers Not based on any specific investigation No intent to be precise

Motivations/uses Gauge consistency of PFAS data within a conceptual site

model (CSM) Identify areas of refinement or exploration

14

PFASOrderofMagnitudeModels

HowMuchPFASinAirisNeededtoContaminateGroundwater?

Assume: PFAS deposits and mixes with precipitation Deposition velocity 3 cm/s 1 m annual precipitation depth

Find by mass balance: 1 ng/m3 in air produces 1,000 ng/l in water

Perspective: 70 – 170 ng/m3 detected in air near Dupont in WV Typical particulate matter concentrations are 5,000 – 10,000 ng/m3

15

WhatPFASEmissionRateProducesObservedAirLevels?

Ballpark Assumptions: PFAS in air at 10 ng/m3

Emission height ~ 30 m Class D/E stability Wind speed ~5 m/s Transport distance ~1,000 to 1,500 m

Guesstimate: Impact Cu/Q of 5.0×10-5 m-2 (Turner’s Workbook) Implied emission Q = 0.008 lb/hr = 70 lb/yr = 0.035 tons/year Significant emission threshold for particulate matter = 100 tons/year

16

PFASAirEmissionEstimates Chromium plating facilities Concentration 4.9 μg/m3 in vented exhaust corresponds to 1

lb/yr PFOS (1) Lake Calhoun, MN mass balance: 36 lb/yr (2,3)

Dupont plant in Washington, WV (3) > 10,000 lb/yr from 1978 through 2002 Peaked at 34,000 lb/yr (1999) = 17 tons/yr

Chemours Fayetteville NC plant NC DENR estimates 2,758 lb/yr GenX emissions in 2018 (4)

17

(1) NAVFAC TR-2243-ENV, March 2004(2) https://www.minneapolisparks.org/_asset/0jd11p/water_resources_report_2015.pdf (1.8×107 m3 and 4.2 yr residence)

https://www.pca.state.mn.us/sites/default/files/c-pfc1-02.pdf (average 108 ppt)(3) Paustenbach et al (2007), J Toxicol Environ Health 1:28-57(4) https://files.nc.gov/ncdeq/GenX/epa-comm-mtg/Abraczinskas-EPA-PFAS-Stakeholder-mtg-Aug14-2018.pdf

PFASModelingStudyExample

18

H.-M. Shin etal. (2012), Atmospheric Environment 51 (2012) 67-74

Soil PFAS levels in the 10’s of ppb (10,000’s ppt)

Air: 200 ng/m3

Soil: 11,000 ng/kgWater: 4,000 ng/l

Soil:TheCriticalPFASReservoir?

19

Atmospheric deposition

Accumulation/Depletion

Infiltration

Leaching

Soil

Groundwater

Direct exposure to PFAS in soil is generally not a “risk driver” EPA RSLs for PFOA & PFOS = 126

ppb; Background ~ 1 ppb However, ppb levels in soil can

supply ppt levels in groundwater for many years

PFASinsoilispotentiallyimportantforsourcecontrol

PFASinSoilNearanEmissionSourceEstimate0.015g/m2 PFOA/PFOSinsoilcolumnbasedon: 10 ng/g of PFOA/PFOS in soil Contaminated depth of 1 m Soil bulk density of 1,500 kg/m3

Estimatedepositionrateof0.009g/m2‐yrbasedon(previousexample): 10 ng/m3 PFOA/PFOS in air deposition velocity of 3 cm/s

20

< 2 years deposition

PFASBackgroundLevelsinVTSoils

1

10

100

1,000

10,000

PFHxA PFHpA PFOA PFNA PFDA PFUnDA PFBS PFHxS PFOS

Concen

tration (ng/kg or p

pt)

Analyte

Quartiles Maximum 95th Percentile Median Minimum Method Detection Limit

21https://anrweb.vt.gov/PubDocs/DEC/PFOA/Soil-Background/PFAS-Background-Vermont-Shallow-Soils-03-24-19.pdf

RegionalPFASDeposition

39,000lb/yr ofemissionsfor50yearsrequiredfor: Level of PFOA+PFOS = 1 µg/kg (VT soils) Land area of 1.5×106 miles (half of U.S.) 0.15 m (6 in) depth Soil bulk density of 1500 kg/m3

PFOAemissionsfromWVmanufacturingplantaloneaveraged14,000lb/yr (1)for50years

22(1) Paustenbach et al (2007), J Toxicol Environ Health 1:28-57

Summary&ConclusionsonModelingAllModelsareWrong,SomeareUseful

Order-of-magnitude models are possiblyinstructive/suggestive, but not conclusive Need to consider other factors Better and more complex models Proper input and diagnostic data for models Site-specific hydrology Leaching parameters Aquifer retardation factors

23

© Sanborn, Head & Associates, Inc.

Soil as a Source to Groundwater Fundamentals and background Leaching‐based screening values Anthropogenic background Screening approaches Treatment/remediation

The focus of this presentation is on PFOA and PFOS. PFAS, including precursors to PFOA and PFOS, have

widely ranging chemistries and properties.

1


Soil is a key media for many releases2

Soil

Groundwater



Soil

Groundwater

Soil‐GW ratio



1. Anderson, Adamson, and Stroo. (2019). Journal of Contaminant Hydrology, 220 59‐65: https://doi.org/10.1016/j.jconhyd.2018.11.011

Soil

Groundwater

U.S. Air Force sites histogram of Soil‐GW Ratios1

324 AFFF sites Source‐zone soil and GW 8 orders of magnitude

variation


PFOA Chemical Structure

Fluorocarbon tail Hydrophobic Lipophobic

5

Throughout the presentation, PFOA molecules are illustrated. These illustrations are not to scale, and numerous other details are not shown, including counterions, water molecules, and solids molecules.

Functional group Hydrophilic High solubility Low volatility

FF F F F

F F F F F F F

F FF

O

O(–)

AirWater

Ionic skeletal and 3D models

Branched isomer models

Surfactant

FF F F FF F F O

O(–)

F F FF F F F


PFOA/PFOS Phase Partitioning6

1. Li, Oliver, and Kookana. (2018). Science of the Total Environment, 628‐629 110‐120: https://doi.org/10.1016/j.scitotenv.2018.01.167

Surfactant behavior

(at higher conc.)

Solid Liquid

Electrostatic interactions

Hydrophobic sorption

Li et al. (2018)1

Not just Kd = Koc × foc



1. Brusseau, Yan, Van Glubt, Wang, Chen, Lyu, Dungan, Carroll, Holguin. (2019). Water Research, 148 41‐50: https://doi.org/10.1016/j.watres.2018.10.0352. Guo, Zeng, and Brusseau. (2020). Water Resources Research, 57: https://doi.org/10.1029/2019WR026667

AirWater

AirLiquidLiquidAir

Brusseau et al. (2019)1 and Guo et al. (2020)2 >80% total retention Greater retention in sand vs. finer‐grains

Dr. Linda AbriolaSERDP/ESTCP air‐water and

NAPL‐water interface partitioning presentation:

https://www.youtube.com/user/SERDPESTCP


Key Factors: Soil and water chem, e.g. Organic carbon Co‐contaminants pH & surface charge Major ions

PFOA/PFOS concentration Previous conditions


For more information, see ITRC PFAS Technical and Regulatory Guidance Document:https://pfas‐1.itrcweb.org/5‐environmental‐fate‐and‐transport‐processes/#5_2

nonlinear

hysteresis

Not to scale


Field Conditions Phase Partitioning Hydraulics Microscale Macroscale

Kinetics/mass transfer

Field conditions: Approach equilibrium Complex/variable Heterogeneous Cannot replicate in a lab

Delicate Disturbed by sampling

9


PFAS in Background Vermont Shallow Soils10

Source, University of Vermont and Sanborn Head: https://anrweb.vt.gov/PubDocs/DEC/PFOA/Soil‐Background/PFAS‐Background‐Vermont‐Shallow‐Soils‐03‐24‐19.pdf

66 locations, 0‐6” depth

Parks, grass areas, forests

13 PFCAs & 4 PFSAs

ΣPFAS (ng/kg) >5,000 [n = 8]2,000‐5,000 [n = 23]1,000‐2,000 [n = 25<1,000 [n = 10]


370

685

1,300

3,580

10

100

1,000

10,000

100,000

ng/k

g

PFOSVT Data

PFOAVT Data

PFOSScreening Values

PFOAScreening Values

median

95th percentile

median

95th percentile

Soil Leaching Values & VT Background11

1. The intent of this aggregate comparison is to contextualize the regulatory and guidance values. The individual data in this study were not collected for comparison to regulatory or guidance values and should not be used for that purpose. 2. “Soil to GW Protection Values” were largely obtained from the ITRC fact sheet spreadsheet updated June 2020 (https://pfas-1.itrcweb.org/fact-sheets/). Some proposed or draft values, which may be on-hold or now replaced with updated values, are also included.


370

685

1,300

3,580

10

100

1,000

10,000

100,000

ng/k

g

PFOSVT Data

PFOAVT Data

PFOSScreening Values

PFOAScreening Values

median

95th percentile

median

95th percentile

Soil Leaching Values & VT Background12

1. The intent of this aggregate comparison is to contextualize the regulatory and guidance values. The individual data in this study were not collected for comparison to regulatory or guidance values and should not be used for that purpose. 2. “Soil to GW Protection Values” were largely obtained from the ITRC fact sheet spreadsheet updated June 2020 (https://pfas-1.itrcweb.org/fact-sheets/). Some proposed or draft values, which may be on-hold or now replaced with updated values, are also included.

Suggest faster leaching

Suggest slower leaching


Common Tools Rely on Key Assumptions and Interpretation

13

Empirical Theoretical

Simple

Complex Site Data

Soil data

Paired Soil / GW data

Lab Tests Models

Generic

GW data

Single‐point leaching


Lab Tests

Single‐point leaching

Consider Empirical and Complex Tools14

Empirical Theoretical

Simple

Complex Site Data

Soil data

Paired Soil / GW data

Models

Generic

GW data

High res.

In‐situ testing(e.g., lysimeter) Column

testing

Kinetic andisotherm studies

Site Specific


PFOA Atmospheric Deposition Case Study15

Column testing and photographs by XDD Environmental, LLC.

1

10

100

1,000

10,000

Soil NearbyGW

Column SPLP

ng/L or n

g/kg

NDs

ND

~0.2 L/kg ~20 L/kg



Column testing and photographs by XDD Environmental, LLC.

1

10

100

1,000

10,000

Soil NearbyGW

Column SPLP

ng/L or n

g/kg

NDs

ND

~0.2 L/kg ~20 L/kg


1

10

100

1,000

10,000

Soil NearbyGW

Column SPLP

ng/L or n

g/kg

NDs

ND


Column testing and photographs by XDD Environmental, LLC. ~0.2 L/kg ~20 L/kg


Remediation/Treatment Options18

DestructionSequestrationSeparationSorption


Ex-Situ Sorption Typically GAC (granular activated carbon) or AIX (anion exchange)

Site‐specific PFAS chain‐length Water matrix Space & pretreatment Combined technologies Community acceptance

19

Hydrophobic sorption

Electrostatic interactions


Other Technologies

In‐situ Stabilization Sorptive media PRBs or injection Thermal/redox [D?]

Ex‐situ Membranes (RO and nano) Anion exchange regeneration Specialty coagulants &

electrochemical precipitation [S?] Foam fractionation [S] Plasma [D] [S] Redox [D] [S?] Sonolysis [D] [S]

20

See ITRC for technology summaries: https://pfas‐1.itrcweb.org/12‐treatment‐technologies/

Air

Water

Very strong

[D] = destructive

[S] = surfactant behaviorleveraged


SummarySorption (F&T and treatment) Many important factors and wide‐ranging case‐study data

Screening Approaches Consider multiple lines of evidence, empirical data

For more information, we recommend:ITRC technical resources for PFAShttps://www.itrcweb.org/Team/Public?teamID=78 Fact sheets Web‐based Tech. Reg. Guidance Document Online Training Materials

21

22

Thank you for your time!Questions?

Stephen G. Zemba, PhD, PE

[email protected] 802.391.8508M 617.225.0225

[email protected] 603.415.6156M 207.337.3662

Harrison R. Roakes, PE

sanborn head has met the standards and requirements of the

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