1

Distribution of PAHs among Sediment Size

Fractions Determined by Thermal Desorption

Gas Chromatography Mass Spectrometry

Jejal Reddy Bathi1, Robert Pitt1, Robert Findlay2,

Shirley E. Clark3

1Department of Civil, Construction and Environmental Engineering

University of Alabama, Tuscaloosa, AL 35487 2Department of Biological Sciences, University of Alabama

Tuscaloosa, AL 35487 3Penn State - Harrisburg, School of Science, Engineering and

Technology, Middleton, PA - 17507

2

Overview of Presentation

Introduction

Thermal Desorption (TD) Method

Development

Sample Collection and Analyses

Conclusions

Question and Answers

3

Introduction

Steps for PAH analyses

Sample preparation

Extraction and Concentration

Detection and Quantification

Liquid-liquid extraction by separatory funnel and Solid Phase Extraction (SPE) are the most common PAH extraction methods for liquid samples.

SPE method is ineffective for liquid samples with high concentrations of solids.

4

Introduction

For solid samples, Soxhlet, automated Soxhlet, and

ultrasonic extraction are the most common PAH

extraction methods.

Disadvantages of traditional methods include,

Time consuming

Labor intensive

Use of large amounts of toxic solvents

Exposure of toxic organic solvents to the

operators

5

Introduction - Fugacity Modeling Contaminant partition constants (KOW, KOC, Henry’s constant) are

key factors in their fate.

Fugacity Level I equilibrium model (Mackay et al. 1992) was used for predicting the phase partitioning of PAHs. The following graph illustrates the effect of KOW and KOC on partitioning onto solids.

0

20

40

60

80

100

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

Log (Kow), Log (Koc)

% o

f P

AH

wit

h S

olid

s

Log (Kow) Log (Koc)

6

After Hurricane Katrina, and other

devastating hurricanes of the 2005 season,

EPA reviewed several monitoring and

cleanup programs in the days following the

events. The selection of the right analytical

and sampling methods for water and

sediment were all found to be very critical

in reducing the risk to the cleanup crews,

emergency workers, and residents.

Katrina oil refinery damage (EPA photo) Waste sorting area with field labs (EPA photo)

Fuel and other material leakage from damaged boats. Hurricane Katrina (NOAA photo)

7

Analytical Method Development

The main transport mechanisms and fate of PAHs in the aquatic environment are closely related to their major associations with particles. Therefore, it is essential that rapid and sensitive analytical tools be used that can measure PAHs in samples having large amounts of suspended sediment.

During the aftermath of natural disasters, homeland security incidents, and accidental releases of hazardous and toxic materials, the rapid analyses of samples is needed to identify areas for priority cleanup and in preventing dangerous exposures to cleanup personnel and residents.

Analytical tools need to be developed and tested on a variety of samples to ensure their applicability to a wide range of emergency situations.

With these objectives in mind, a TD-based GC/MSD method was developed and tested using urban stream sediments for PAH contamination.

8

TD Method Development The TD analytical method is rapid, uses no solvent, and is

less labor intensive than other PAH analytical methods, especially for samples having high sediment concentrations.

TD uses elevated temperatures as a means to directly transfer the analytes from solid sample matrices to the gaseous analytical system of the GC/MSD.

The desorbed analytes are concentrated in a cyrotrap at the head of the GC column and are then re-vaporized into the column for separation and final detection.

Final desorption temperature and temperature holding times are two important factors to be optimized for better recovery of PAHs from solid matrices.

9

Direct thermal extraction and

analysis technique

SIS Thermal desorption unit

10

TD Method Development A desorption temperature of 350oC produced the largest

peak areas for the individual PAHs, for the tested range of

temperatures 250oC to 375oC with 25°C step changes.

A final temperature holding time of 15 min produced

maximum peak areas for the individual PAHs in the

resulting chromatograms.

11

TD Method Interferences

Other major findings included the addition of small amounts of copper to avoid interfering sulfur compounds and freeze drying the samples to reduce the moisture content in the samples to prevent ice blockages in the GC column. Local urban stream sediments were sufficiently dried using a conventional drying oven.

Chromatogram obtained by TD/GC/MS

method for the standard NIST PAH sediment

sample which was collected at Chesapeake Bay

at the mouth of Baltimore Harbor

12

TD Method Detection Limits

DL = Y0 + SyZα

(McCormick and Roach 1987)

NIST sediment was tested in

the weight range 3 – 60mg

PAH R2 Detection

Limit (ng)

Naphthalene 98.5 9.63

Fluorene 96.4 2.62

Phenanthrene 97.1 6.37

Anthracene 94.1 3.83

Fluranthrene 98.8 2.67

Pyrene 93.2 9.81

Benzo(a)anthracene 96.8 2.25

Chrysene 96.5 2.63

Benzo(b)flouranthrene 97.6 4.15

Benzo(a)pyrene 97.5 4.2

Indeno(1,2,3-cd)pyrene 93.1 1.34

Dibenz(a,h)anthracene 52.2 1.05

Benzo(ghi)perylene 97.1 0.97

y = 1.2481x + 6.1919

R2 = 0.9854

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Amount of Analyte in NIST Standard (ng)

Calc

ula

ted

Am

ou

nt

of

An

aly

te (

ng

)

Naphthalene

13

TD Method Recovery Calculations

PAH

% Recovery

from Solid

Samples

Acceptable Range of %

Recovery from EPA

Methods (Aqueous

Samples)

Acceptable Range of %

Recovery from Standard

Methods (Aqueous

Samples)

Naphthalene 125 D – 122 21 – 133

Fluorene 142 D – 142 59 – 121

Phenanthrene 110 D – 155 54 -120

Anthracene 104 NG NG

Fluranthrene 62 14 – 123 26 – 137

Pyrene 33 D – 140 52 – 115

Benzo(a)anthracene 109 33 – 143 33 – 143

Chrysene 140 17 – 168 17 – 168

Benzo(b)flouranthrene 35 24 – 159 24 – 159

Benzo(a)pyrene 41 17 – 163 17 – 163

Indeno(1,2,3-cd)pyrene 34

NG NG

Dibenz(a,h)anthracene 46 NG NG

Benzo(ghi)perylene 43 NG NG

14

Effect of Recovery by Particle Size Concentrations of PAHs in three replicates of two coarse samples were

compared with PAH concentrations in the same samples that were

ground to <180 µm to test the effect of particle sizes on PAH recovery.

Only one PAH of one sample was significantly affected by grinding.

PAH

ANOVA P Value (95% C.I) of Comparing Concentrations

Comparing the Coarser 710 - 1400µm

with Its Ground Sample Comparing the Coarser 1400 - 2800µm

with Its Ground Sample

Naphthalene 0.122 0.128

Fluorene 0.064 0.118

Phenanthrene 0.618 0.052

Anthracene 0.776 0.204

Fluranthrene 0.786 0.135

Pyrene 0.516 0.076

Benzo(a)anthracene 0.052 0.368

Chrysene 0.36 0.249

Benzo(b)flouranthrene 0.342 0.409

Benzo(a)pyrene 0.048 0.45

Indeno(1,2,3-cd)pyrene 0.175 0.67

Dibenz(a,h)anthracene 0.376 0.294

Benzo(ghi)perylene 0.100 0.660

15

Sampling Sites

Sediment samples were collected from three urban creeks in the Tuscaloosa and Northport, Alabama, areas

Site 1: Cribbs Mill Creek

Source areas: medium density two story family home residential area

No history of sanitary sewage contamination (Pitt, et al 2005)

Site 2: Hunter Creek

Source areas: automobile service commercial areas, heavy traffic along McFarland Blvd., and runoff from trailer park residential areas

Site 3: Carroll Creek

Source areas: A residential area on one side and forested lands on the other side of the creek

Has a recent history (in 2006) of sanitary sewer overflows (SSOs) into the creek (ADEM Consent Order No. 07-139-CWP to City of Northport)

16

Sample Particle Size Distributions Five sediment samples were collected from each of the three

creeks.

All sediments were fractionated into nine size (µm) ranges <45,

45-90, 90-180, 180-355, 355-710, 710-1400, 1400-2800,

>2800(w/o large organic matter (LOM)) and > 2800 (LOM only).

0

10

20

30

40

50

60

70

80

90

100

10 100 1000 10000Size (um)

% L

ess t

han

Hunter Creek Cribbs Mill Creek Carroll's Creek

17

COD Associations by Particle Size COD analyses were conducted to indicate the amount of organic

material in the samples (a rapid and commonly available analytical method), an important factor in PAH associations.

Median mass of the sediment COD was associated with 355 µm particles.

0.E+00

2.E+07

4.E+07

6.E+07

8.E+07

1.E+08

1.E+08

1.E+08

2.E+08

<4545 - 9

090 - 1

80

180 - 355

355 - 710

710 - 1400

1400 - 2800

>2800

Size Range (µm)

CO

D (

mg/

Kg)

Hunter Carroll's Cribbs

0

20

40

60

80

100

10 100 1000 10000Size (um)

% o

f T

ota

l C

OD

Le

ss T

ha

n

Hunter Carroll 's Cribb's Mill

Cribbs Mill Creek Hunter Creek Carroll's Creek

1.60E+09 1.50E+09 1.30E+09

COD in large organic material fraction >2800 µm (LOM), COD much larger than in

other sample sizes:

18

Thermal Chromatography used to Identify Major Sample

Components

Temperature range of 104 – 550 °C

(total volatile fraction)

Temperature range of 240˚C – 365 ˚C

(mostly leaves and grass fraction)

Temperature (oC) Material Lost at These

Temperatures

up to 104 Moisture

104 - 240 Paper debris

240 - 365 Leaves and grass

365 - 470 Rubber

470 - 550 Asphalt

Above 550 Remaining material is inert

Temperature

Range (ºC)

LOM % Weight Loss

Hunter Carroll's

104 - 240 8.6 20.4

240 - 365 42.5 33.5

365 - 470 28.3 3.9

470 - 550 1.3 0.9

% Inert Material 19.2 41.4

02468

101214161820

<4545 - 9

0

90 - 180

180 - 355

355 - 710

710 - 1400

1400 - 2800

>2800 (w/o LO

M)

Size Range (µm)

% o

f W

eigh

t Lo

ss

Hunter Carroll's Cribb's

02468

1012141618

<4545 - 9

0

90 - 180

180 - 355

355 - 710

710 - 1400

1400 - 2800

>2800 (w/o LO

M)

Size Range (µm)

% O

f W

eig

ht

Loss

Hunter Carroll's Cribbs

19

Log(y) = 1.1694Log(x) + 6.9732

R2 = 0.9393

3

5

7

9

0 0.5 1 1.5 2

Log(% Total Weight Loss)

Log(

COD

)

Log(y) = 1.0739Log(x) + 6.9425

R2 = 0.805

3

5

7

9

-0.5 0 0.5 1 1.5 2 2.5

Log(% Total Weight Loss)

Log(

COD

)

y = 5E+06x + 5E+07

R2 = 0.808

0.E+00

2.E+07

4.E+07

6.E+07

8.E+07

1.E+08

1.E+08

1.E+08

2.E+08

0 4 8 12 16 20 24

% Total Weight Loss

CO

D (

mg/

Kg)

COD vs. Expected Leaves and Grass Fraction

Cribbs Mill Creek Hunter Creek

Carroll’s Creek

P < 0.005

P < 0.005

P < 0.005

Creek

ANOVA P Value of

Regression

Slope Constant

Cribbs Mill Creek < 0.005 < 0.005

Hunter Creek < 0.005 < 0.005

Carroll's Creek < 0.005 < 0.005

20

PAH concentration

trends with sediment

size are similar to the

trends for COD and

the leaves and grass

fractions.

The smaller

(<180μm) and larger

(>710μm) particles

were found to have

higher concentrations

of PAHs than the

intermediate sizes

Concentrations

of PAHs by

Particle Sizes

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)Naphthalene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

3500

3000

2500

2000

1500

1000

500

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)

Fluorene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

90 -

180

45 -

90<

45

4000

3000

2000

1000

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)

Anthracene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

7000

6000

5000

4000

3000

2000

1000

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)

Dibenz(a,h)anthracene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

8000

7000

6000

5000

4000

3000

2000

1000

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)

Benzo(g,h,i)perylene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

4000

3000

2000

1000

0

Size Range (µm)

Co

nce

ntr

ati

on

(µ

g/

Kg

)

Indeno(1,2,3-cd)pyrene

21

Almost all of the

sediment PAHs are

associated, by mass, in

the intermediate

particle size fraction

(90 to 710 µm), even

though this size range

had the lowest

concentrations

Size (µm)

% Average

dry weight

of Sediment

<45 1.1

45 – 90 2.8

90 - 180 14.4

180 - 355 46.4

355 - 710 27.4

710 - 1400 3.5

1400 - 2800 1.8

Large organic

matter0.3

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

30000

25000

20000

15000

10000

5000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

tNaphthalene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

50000

40000

30000

20000

10000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

t

Benzo(g,h,i)perylene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

35000

30000

25000

20000

15000

10000

5000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

t

Dibenz(a,h)anthracene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

20000

15000

10000

5000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

t

Anthracene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

25000

20000

15000

10000

5000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

t

Fluorene

Leav

es

> 28

00

1400

- 28

00

710 - 1

400

355 - 7

10

180 - 3

55

90 -

180

45 -

90<

45

35000

30000

25000

20000

15000

10000

5000

0

Size Range (µm)

% M

ass A

sso

cia

tio

n w

ith

Se

dim

en

t

Indeno(1,2,3-cd)pyrene

Mass of PAHs by Urban Sediment

Particle Sizes

22

Conclusions

When discharged into the aquatic environment, PAHs are mostly associated with particulate matter, rather than in the dissolved form.

Thermal desorption (TD) is rapid, minimizes the likelihood for human errors and contamination, and uses no solvents.

The leaf and grass content, COD and PAH concentrations in the urban creek sediments showed similar trends: smaller and larger sized particles were associated with higher concentrations compared to the intermediate sized particles.

However, most of the mass of the PAHs were associated with the intermediate particle sizes (90 – 710 µm) in the stream sediments which were in the greatest abundance, even though their PAH concentrations were the lowest.

23

Acknowledgments

NSF EPSCoR, COSS research center for funding this research work

Fellow graduate students in the department of civil engineering at The University of Alabama

Disclaimer:

This material is based upon work supported by the National Science Foundation under Grant No. EPS-0447675. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

24

Thank you

Questions?