incorporation of weathering in pah source apportionment

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Incorporation of Weathering in PAH Source Apportionment Caroline Tuit and Jeffrey Rominger National Environmental Measurement Conference August 11, 2017 Washington DC

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Page 1: Incorporation of Weathering in PAH Source Apportionment

Incorporation of Weathering in PAH Source Apportionment

Caroline Tuit and Jeffrey Rominger

National Environmental Measurement Conference

August 11, 2017Washington DC

Page 2: Incorporation of Weathering in PAH Source Apportionment

2Copyright Gradient 2017

PAH Urban Sediment Sites = High Stakes Allocations

ROD Estimated Clean-up Costs

ā€¢ Ottawa River ($49 Million)

ā€¢ Thea Foss Waterway ($105 Million)

ā€¢ Lower Duwamish Waterway ($342 Million)

ā€¢ Gowanus Canal ($506 Million)

ā€¢ Portland Harbor ($1.05 Billion)

ā€¢ Extremely expensive clean-ups

ā€¢ Multiple Contaminants of Concern

ā€¢ Multiple Sources

ā€¢ Complex Histories

ā€¢ Dynamic Environment

ā€¢ Complex and Weathered Fingerprints

Forensics tools are typically needed to allocate PAH sources

Page 3: Incorporation of Weathering in PAH Source Apportionment

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Key Findings

ā€¢ PAHs are subject to extensive weathering in sediment sites

ā€¢ Water-washing models can approximate weathering effects on PAH fingerprints

ā€¢ PAH source apportionment models rely on well-defined end-members

ā€¢ Evaluation of weathering trends in PAH source apportionment models can

ā–Ŗ Link upland sources to sediment end-members

ā–Ŗ Identify where weathering trends may obscure mixing trends

Page 4: Incorporation of Weathering in PAH Source Apportionment

4Copyright Gradient 2017

Polycyclic Aromatic Hydrocarbons (PAHs)

ā€¢ PAHs can be divided into parent (8270) or alkylated (8270 SIM)

ā€¢ Typical anthropogenic sources:

ā–Ŗ Pyrogenic (burning of coal, petroleum, wood etc.; coal tar; creosote)

ā–Ŗ Petrogenic (oil; gasoline; diesel; asphalt)

ā–Ŗ Urban background (weathered mix of petrogenic and pyrogenic sources)

ā€¢ The pattern of alkylated PAHs can distinguish the PAH source as petrogenic or pyrogenic

ā€¢ Typical source concentrations

ā–Ŗ Crude oil: 0.2 to 7 wt %

ā–Ŗ Coal tar: up to 70 wt %

0

0.2

Petrogenic

0

0.1

0.2

0.3Pyrogenic

LMW (2-3 ring) HMW (4-6 ring)

0

0.1

0.2

N0

N1

N2

N3

N4

AC

YA

CE F0 F1 F2 F3 A0

P0

P1

P2

P3

P4

D0

D1

D2

D3 FL PY

FL1

BA

A C0

C1

C2

C3

C4

BB

FB

KF

BA

P IN DA

GH

I

Urban Runoff

2-Methylnaphthalene

Page 5: Incorporation of Weathering in PAH Source Apportionment

5Copyright Gradient 2017

PAH Weatheringā€¢ Evaporationā€”most PAHs are

non-volatile

ā€¢ Biodegradationā€”Slow, mechanisms are poorly understood

ā–Ŗ Rate and extent correlated with the number of aromatic rings and the presence/absence of side chains

ā€¢ Water-washingā€”Controlled by the aqueous solubility of the individual PAH

ā–Ŗ Solubility of PAHs decreases with number of rings and increasing alkylation

Sources: Haritash, AK; Kaushik, CP. 2009. "Biodegradation aspects of polycyclic aromatic hydrocarbons (PAHs): A review." J. Hazard. Mater. 169(1-3):1-15; Neff, JM; Burns, WA. 1996. "Estimation of polycyclic aromatic hydrocarbon concentrations in the water column based on tissue residues in mussels and salmon: An equilibrium partitioning approach." Environ. Toxicol. Chem. 15(12):2240-2253.

3

4

5

6

7

8

9

100 150 200 250 300

Log

K OW

Molecular WeightAfter Neff and Burns (1996)

PAHs

P0/A0 Series

N0 Series

C0/BaA Series

Water-washing may approximate other weathering

processes

Page 6: Incorporation of Weathering in PAH Source Apportionment

6Copyright Gradient 2017

PAH Weathering

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

N C1-N C2-N C3-N C4-N

Petrogenic Weathering Trend

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

N C1-N C2-N C3-N C4-N

Pyrogenic Weathering Trends

Weathering (e.g., water-washing) can alter PAH distributions preferentially removing low molecular weight (LMW) and parent PAHs

Page 7: Incorporation of Weathering in PAH Source Apportionment

7Copyright Gradient 2017

PAH Forensics ā€“ Typical Allocation Techniques

Principal Component Analysis (PCA)

ā€¢ A statistical tool widely used to determine the number of dominant chemical fingerprints present in the system and examination of relationships between samples and putative sources

ā€¢ Can look at many variables (PAH analytes) at once

Important considerations

ā€¢ Evaluate data for analytical artifacts such as non-detects and low concentrations

ā€¢ Normalize data to eliminate bias due to concentration differences (total normalization) or analytes (variance scaling)

1

23

Page 8: Incorporation of Weathering in PAH Source Apportionment

8Copyright Gradient 2017

PAH Forensics ā€“ Typical Allocation TechniquesReceptor Modeling

ā€¢ Many Techniques: EPA UMIX; EPA Positive Matrix Factorization; Polytopic Vector Analysis; Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS)

ā€¢ An iterative linear algebra method in which the end-member fingerprints that contribute to the sample data are identified and optimized such that the unexplained variance in the data is minimized

ā€¢ Receptor modeling further identifies the fraction that each end-member contributes to every sample

Important Considerations

ā€¢ Well defined end-members

ā€¢ Link end-members to site-specific sources

ā€¢ Evaluate how weathering effects source signatures and end-members

EWP: 55% Tar: 44%

ModelMeas.

Page 9: Incorporation of Weathering in PAH Source Apportionment

9Copyright Gradient 2017

Weathering Model

ā€¢ Based on theoretical model of Short and Heinz (1997) used to identify Exxon Valdez oil in Prince William Sound

ā€¢ Assumptions:

ā–Ŗ Water-washing dominates weathering

ā–Ŗ Equilibration of a small amount of PAH-containing material (NAPL) with a larger volume of clean water

ā–Ŗ PAH concentration calculated separately based on individual KOW

ā€¢ Iterative Depletion: after equilibration, the volume of water is replenished with clean water, and the process repeats itself

ā€¢ The ratio of clean water to NAPL is specified VWater/VNAPL ~10

ā€¢ Higher volume ratios would result in faster weathering; Burns et al. (1997) used 600-700

Short and Heintz (1997); Kow available in Neff and Burns, (1996); Burns et al. (1997).

Page 10: Incorporation of Weathering in PAH Source Apportionment

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Model Equations

š¶š‘š“š‘ƒšæ,š‘–š‘‰š‘š“š‘ƒšæ = š¶š‘š“š‘ƒšæ,š‘“š‘‰š‘š“š‘ƒšæ + š¶š‘¤š‘Žš‘”š‘’š‘Ÿ,š‘“š‘‰š‘Šš‘Žš‘”š‘’š‘Ÿ

Where:CNAPL,i = The initial PAH concentration in the NAPLVNAPL = The volume of NAPLCNAPL,f = The finishing PAH concentration in the NAPL volume after a

water-washing periodCwater,f = The finishing PAH concentration in the waterVwater = The volume of water in contact with the NAPL

š¶š‘š“š‘ƒšæ,š‘“ = š¾š‘œš‘¤š¶š‘¤š‘Žš‘”š‘’š‘Ÿ,š‘“

š¶š‘š“š‘ƒšæ,š‘“š‘–š‘›š‘Žš‘™ = š¶š‘š“š‘ƒšæ,š‘– 1 +š‘‰š‘Šš‘Žš‘”š‘’š‘Ÿ

š‘‰š‘š“š‘ƒšæš¾š‘œš‘¤

āˆ’š‘›

Page 11: Incorporation of Weathering in PAH Source Apportionment

11Copyright Gradient 2017

Important Considerations

ā€¢ NOT quantitativeā€”allows evaluation of fingerprint evolution, not age dating of spills

ā€¢ Most useful in regions with sediment disturbance:

ā–Ŗ Tidal resuspension

ā–Ŗ Storm surge

ā–Ŗ Propeller wash

ā–Ŗ Dredging

ā€¢ Requires well known starting compositions

Page 12: Incorporation of Weathering in PAH Source Apportionment

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Literature Study: Creosote WeatheringAfter Stout et al. (2005); Stout et al. (2001); and Brenner et al. (2002)

ā€¢ PAH weathering based on the Eagle Harbor Superfund Site

ā€¢ Identified 3 source compositions

ā–Ŗ Creosote: pyrogenic; enriched in naphthalene and phenanthrene; high concentration

ā–Ŗ Natural Background: weathered pyrogenic; tPAH < 5 mg/kg

ā–Ŗ Urban Background: enriched in HMW PAHs; tPAH 10-20 mg/kg

0

0.1

0.2

0.3

0.4

Creosote

0

0.05

0.1

0.15

Natural Background

0

0.02

0.04

0.06

0.08

0.1

0.12

N0

N1

N2

N3

N4

Acl

Ace F0 F1 F2 F3 AN P0

P1

P2

P3

P4

D0

D1

D2

D3 FL PY

FP1

BaA C

0C

1C

2C

3C

4B

bF

BkF

BaP ID DA

BgP

Urban Background

Page 13: Incorporation of Weathering in PAH Source Apportionment

13Copyright Gradient 2017

Literature Study: Creosote Weathering

ā€¢ Creosote Weathering

ā–Ŗ Loss of the LMW PAHs

ā–Ŗ Loss of parent PAHs

ā–Ŗ Pyrogenic ratios are still apparent in HMW PAHs

0

0.1

0.2

0.3

0.4

Creosote

0

0.1

0.2Slightly Weathered

0

0.05

0.1

0.15

0.2

Moderately Weathered

0

0.1

0.2

0.3

N0

N1

N2

N3

N4

Acl

Ace F0 F1 F2 F3 AN P0

P1

P2

P3

P4

D0

D1

D2

D3 FL PY

FP1

BaA C

0C

1C

2C

3C

4B

bF

BkF

BaP ID DA

BgP

Severely Weathered

Page 14: Incorporation of Weathering in PAH Source Apportionment

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Principal Component Analysis: Creosote Weathering

ā€¢ Modeled water washing trend follows literature weathering trend

ā€¢ Non-detect effect seen in final water-washing steps

Upland Source

Fresh

Slightly

Moderately

Severely

Urban Background

Natural Background

Fresh

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4

PC

2 (

18

.4%

)

PC1(60.1%)

Upland Source

Fresh

Slightly

Moderately

Severely

Urban Background

Natural Background

Fresh

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4

PC

3(1

6.1

%)

PC1(60.1%)

Page 15: Incorporation of Weathering in PAH Source Apportionment

15Copyright Gradient 2017

Literature Study: Creosote Weathering

0

0.1

0.2

0.3

0.4

Creosote

0

0.1

0.2

Slightly Weathered

0

0.05

0.1

0.15

0.2

Moderately Weathered

0

0.1

0.2

0.3

N0

N1

N2

N3

N4

Acl

Ace F0 F1 F2 F3 AN P0

P1

P2

P3

P4

D0

D1

D2

D3 FL PY

FP1

BaA C

0C

1C

2C

3C

4B

bF

BkF

BaP ID DA

BgP

Severely Weathered

0

0.05

0.1

0.15

0.2

0.25

0.3

0

0.05

0.1

0.15

0.2

N0

N1

N2

N3

N4

Acl

Ace F0 F1 F2 F3 AN P0

P1

P2

P3

P4

D0

D1

D2

D3 FL PY

FP1

BaA C

0C

1C

2C

3C

4B

bF

BkF

BaP ID DA

BgP

0

0.05

0.1

0.15

0.2

0.25

Modeled Fingerprint

Page 16: Incorporation of Weathering in PAH Source Apportionment

16Copyright Gradient 2017

Case Study 2: MGP Impacted

ā€¢ Urban Sediment Superfund Site

ā€¢ History of Combined Sewer Overflows and Manufactured Gas Plant (MGP) Operations

ā€¢ Remedial Investigation with publicly available tPAH17

analyses

ā€¢ Total normalized; Excludes samples with > 30% non-detected (ND) analytes and concentrations < 1 mg/kg

Question: How does weathering of MGP tar change the parent PAH fingerprint?

Page 17: Incorporation of Weathering in PAH Source Apportionment

17Copyright Gradient 2017

Principal Component Analysis of Parent PAH Fingerprints

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

PC

2(1

2.7

%)

PC1 (68.7%)

Native Sediment

Sediment

1

3

2

3 PotentialSources

Page 18: Incorporation of Weathering in PAH Source Apportionment

18Copyright Gradient 2017

Principal Component Analysis of Parent PAH Fingerprints

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

PC

2(1

2.7

%)

PC1 (68.7%)

Native Sediment

Sediment

0.0

0.1

0.2

0.3

0.4

0.0

0.1

0.2

0.3

0.4

0.0

0.1

0.2

0.3

0.4

Page 19: Incorporation of Weathering in PAH Source Apportionment

19Copyright Gradient 2017

Principal Component Analysis of Parent PAH Fingerprints

Crude oilDiesel

#4 Fuel

#6 Fuel

Hi S gas oil

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

PC

2(1

2.7

%)

PC1 (68.7%)

Native Sediment

Sediment

MGP Tar (EPRI 2000)

Petroleum Sources (EPRI 2000)

Page 20: Incorporation of Weathering in PAH Source Apportionment

20Copyright Gradient 2017

Principal Component Analysis of Parent PAH Fingerprints

Crude oilDiesel

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

PC

2(1

2.7

%)

PC1 (68.7%)

Native Sediment

Sediment

MGP Tar (EPRI 2000)

Petroleum Sources (EPRI 2000)

Most of the Sediment impacts can be explained by weathering of the MGP tar sources

Page 21: Incorporation of Weathering in PAH Source Apportionment

21Copyright Gradient 2017

Conclusions

ā€¢ It is critically important to evaluate weathering trends in Principal Component and Receptor Modeling

ā–Ŗ No fingerprint will survive contact with the environment intact

ā€¢ Weathering can shift pyrogenic fingerprints into petrogenic patterns for LMW PAHs

ā€¢ Weathering trends can obscure mixing trends

ā–Ŗ Where this occurs it may be important to incorporate tPAHconcentration or other source tracers into the PAH analysis

ā€¢ Weathering can help identify more appropriate source compositions for use in receptor modeling