Allison Taylor, Jie Wang, Daniel Schlenk and Jay Gan

Department of Environmental Science University of California, Riverside, CA 92521

“Priority” Organic Pollutants (HOCs) • Chlorinated pesticides

• PCBs/PBDEs FACT 1: • PAHs Strong sorption • Dioxins

• Chlorinated pesticides

• PCBs/PBDEs FACT 2: • PAHs Aged • Dioxins

2

DDT • Paul Hermann Müller, Nobel Prize in Physiology or

Medicine, 1948 • During World War II, control malaria

and typhus among civilians and troops • Agricultural insecticide since 1945 • Banned in 1972 in the U.S.

3

Aging and Bioavailability plant roots

microbes

organic matter

dissolved OM Freely dissolved benthic invertebrates

4

5

plant roots

benthic invertebrates

microbes

organic matter

dissolved OM

Freely dissolved

Bioaccessible

Aging and Bioavailability

6

plant roots

benthic invertebrates

microbes

organic matter

dissolved OM

Freely dissolved

Bioaccessible

Non-accessible

Aging and Bioavailability

7

plant roots

benthic invertebrates

microbes

organic matter

dissolved OM

Freely dissolvedBioaccessible

Non-accessible

Aging and Bioavailability

Measuring Bioavailability

Reversibly bound Freely

dissolved

Irreversibly bound

Reversibly bound Freely

dissolved

Irreversibly bound

Reversibly bound Freely

dissolved

Irreversibly bound

Equilibrium sampling

Total concentration Bioaccessibility Cfree

Reichenberg and Mayer, ET&C, 2006, 1239-1245

Bioavailability

Reichenberg and Mayer, 2006, Environ. Toxicol. Chem. 25, 1239-1245

Total concentration

BioaccessibleConcentration

Freely dissolved

ConcentrationRisk

Bioavailability

Freely dissolved concentration Cfree

The potential for a chemical to undergo spontaneous processes, e.g., diffusion and partitioning

Bioaccessibility

The actual amount of a chemical that is or may become available within a given time and under given conditions

Bioavailability Methods

Bioaccessibility

• Partial desorption• Weak acid extraction• Mild solvent extraction• Gut fluid extraction• Cyclodextrin extraction• Tenax adsorption

extraction• Isotope dilution

method (IDM)

Cfree

• Passive samplers• DGT• Polyethylene devices

(PEDs)• Semi-permeable

membrane devices (SPMDs)

• Polyoxymethylene (POM)

• Solid phase micro-extraction (SPME)

� Health Warnings:

Study I. Aged POPs at the Palos Verdes Superfund Site

US EPA, 2010

A Sediment Core Experiment•Hypothesis:

• Contaminant aging has resulted in reduced bioavailability.

210Pb Dating

Total Concentrations

Total concentration profiles of PCBs and DDTs in (A) 8C and (B) 3C cores in µg/kg dry weight (d.w.) of sediment.

1860

1880

1900

1920

1940

1960

1980

2000

0.05.0x10

1

1.0x102

1.5x102

2.0x102

Total Concentration (µg/kg)Ye

ar

PCB 153 PCB 70 PCB 52 1860

1880

1900

1920

1940

1960

1980

2000

0.02.0x10

3

4.0x103

6.0x103

8.0x103

1.0x104

Total Concentration (µg/kg)

Year

p,p'-DDD p,p'-DDE o,p'-DDE

1920

1940

1960

1980

2000

0.05.0x10

2

1.0x103

1.5x103

2.0x103

Total Concentration (µg/kg)

Yea

r

PCB 153 PCB 70 PCB 52

1920

1940

1960

1980

2000

0.02.0x10

4

4.0x104

6.0x104

8.0x104

1.0x105

Total Concentration (µg/kg)

Yea

r

p,p'-DDD p,p'-DDE o,p'-DDE

A) B)

Tenax Results

3C 8C

Conclusions I

• DDT residues were extensively “aged”.• Due to aging, only a very small fraction of DDTs in the marine

sediment was “bioaccessible”.• DDTs in surface sediment also showed very low bioaccessibility.

• DDT residues were “aged” elsewhere before deposition onto the ocean floor

• Implications:• Risks much lower than expected from total concentration• EPA decided to use MNA (“monitored natural attenuation”)

instead of capping.

Isotope-labeled HOCs

Historically-contaminated soil

Eisenia fetida ultrasonic extraction

SPE purification

Bioaccumulation assay

Study II. A Direct Method to Test Aging

Isotope-labeled HOCs

Historically-contaminated marine sediment

Nereis virens

SPE purification

ultrasonic extraction

Bioaccumulation assay

Isotope-labeled HOCs

Historically-contaminated freshwater sediment

Lumbriculus variegatus

SPE purification

ultrasonic extraction

Bioaccumulation assay

Isotope-labeled HOCs

Historically-contaminated soil/sediment

Tenax beads

Spiked soil/sediment

centrifuging &transferring beads

ultrasonicextraction

transferring

Tenax desorption

PCB52 PCB70 DDE DDD DDT0.0

0.4

0.8

1.2

Bio

acce

ssib

ility

native HOCs labeled HOCs

soil A

PCB52 PCB70 DDE DDD DDT0.0

0.4

0.8

1.2soil B

PCB52 PCB70 DDE DDD DDT0.0

0.4

0.8

1.2sediment 8C

PCB52 PCB70 DDE DDD DDT0.0

0.4

0.8

1.2sediment 6C

PCB52 PCB70 DDE DDD DDT0.0

0.4

0.8

1.2sediment FW

Tenax F24h of native HOCs were consistently smaller than those for isotope labeled HOCs, suggesting reduced bioaccessibility due to aging

Tenax24h

total

CFC

=

PCB52 PCB70 DDE DDD DDT0

5

10

15

20 B

iota

-to-s

oil/s

edim

ent a

ccum

ulat

ion

fact

ors

native HOCs labeled HOCssoil A

PCB52 PCB70 DDE DDD DDT0

4

8

12soil B

PCB52 PCB70 DDE DDD DDT

0.0

0.1

0.2

0.3sediment 8C

PCB52 PCB70 DDE DDD DDT0.0

0.1

0.2

0.3

sediment 6C

PCB52 PCB70 DDE DDD DDT0

1

2

3

4sediment FW

The BSAF values of native HOCs were consistently lower than those for isotope labeled HOCs, clearly indicating aging effect on bioavailability of POPs in environmental matrices

BSAF =Cworm / f lipCtotal / foc

-1 0 1 2 3-1

0

1

2

3

log

labe

led

HO

Cs/

nativ

e H

OC

s (T

enax

)

log labeled HOCs/native HOCs (worm)

y = (0.95±0.09)x + (-0.12±0.14)R2=0.82p<0.05

• Ratios of labeled HOCs to native HOCs accumulated in earthworm, against against with the ratios of Tenax F24h.

• Highly significant linear correlation, with R2 = 0.82, and slope close to 1.

Conclusions II•Compared to freshly spiked chemicals, bioaccumulation of

aged residues was much lower•The same conclusion was made in marine sediment,

freshwater sediment and soil, for different invertebrates•The use of chemically based measurement closely

predicted bioaccumulation•The use of isotope labels is a direct and convincing

technique to demonstrate the effect of aging on contaminant bioavailability.

Funding $upport