Solid Phase Microextraction (SPME) to Assess the Contribution of PAHs.ppt

chemistry

1. Use of Solid Phase Microextraction
(SPME) to Assess the Contribution
of PAHs to Toxicity of Sediments
at a Former Manufacturing Plant
Battelle Sediment Conference
Jacksonville, Florida
February 5, 2009
Susan Kane Driscoll, Margaret McArdle, and Pieter Booth

2. Introduction
•Former manufacturing and assembly
plant
•Several site investigations have been
conducted, subject to audit by state
•Area of concern:
–Brook
•Contaminants
of concern:
–PAHs, metals,
phthalates, PCBs,
and pesticides

3. Site Habitat and Surroundings
•Urban setting with mixed
industrial, commercial,
and residential uses
•Stream quality is impacted
by typical urban stressors
–Impervious surfaces influence
stream flow
–Riparian habitat loss from
development
–Degradation from storm water
discharges
–Ephemeral water flow limits
fish community

4. Conceptual Model: Brook
•Assessment Endpoint 2:
Reduced survival, growth, or
reproduction of benthic invertebrates in the brook
•Measurement Endpoints:
Comparison to sediment benchmarks, chronic
toxicity tests, and PAH toxicity models

5. Exposure Assessment:
Freshwater Brook
•25 sediment samples screened for metals
and SVOCs
•14 sediment samples selected for further
analysis
–Chronic sediment toxicity with Hyallela azteca
–Pesticides
–34 PAHs
–Total organic carbon
–Grain size
–Black carbon
–Solid-phase microextraction (SPME) and analysis of
34 PAHs in pore water

6. Freshwater Brook:
Sample Locations

7. Freshwater Brook
•Sediment
–Lead was detected up to 6,400 mg/kg
–Zinc was detected up to 900 mg/kg
–Antimony was detected up to 200 mg/kg
–Total PAHs were detected up to 900 mg/kg
–Pthalates were detected up to 1,000 mg/kg
–Total PCBs were detected up to 1 mg/kg
–Total DDT was detected up to 0.09 mg/kg
•Porewater
–SPME used to measure PAHs in a subset of
samples

8. Effects Assessment for PAHs
based on U.S. EPA Guidance
Documents
•U.S. EPA. 2003—Procedures for the Derivation
of Equilibrium Partitioning Sediment
Benchmarks (ESBs) for the Protection of
Benthic Organisms: PAH Mixtures
•U.S. EPA. 2000—Draft Methods for the
Derivation of Site-Specific Equilibrium
Partitioning Sediment Guidelines (ESGs) for
the Protection of Benthic Invertebrates:
Nonionic Organics

9. U.S. EPA ESB Approach
•Calculates “toxic units” for 34 PAHs as:
–Note: EPA FCV provided as mg/kg OC or
mg/L
•If Sum-TU for 34 PAHs < 1.0,
concentration of total PAHs in sediment
is protective of benthic invertebrates
C
SED, PAH
i
Final Chronic Value
PAH
i

10. U.S. EPA ESB Approach
•Three methods used to calculate Σ-TUs:
–One-phase model estimates PAHs in pore
water from PAHs in bulk sediment and TOC
–Two-phase model estimates PAHs in pore
water from PAHs in bulk sediment, TOC, and
black carbon
–Solid phase microextraction (SPME) method
directly measures PAHs in pore water

11. One-Phase Model for Calculating
the Sum of Toxic Units
where:
C
SED= concentration of each PAH in sediment (µg/kg dry wt)
C
W= concentration of truly dissolved PAH in pore water (µg/L)
f
TOC= weight fraction of TOC (kg organic carbon/kg dry wt)
K
OC= organic carbon-water partition coefficient (L/kg)
The equation is rearranged and used to solve for
C
W. C
Wfor each PAH is divided by its
corresponding F
CVto calculate a toxic unit.
C
SED/C
W= f
TOC･K
oc

12. Two-Phase Model for Calculating
the Sum of Toxic Units
C
SED/C
W= f
NPOC･K
OC+f
BC･K
BCC
W
n-1
where:
C
SED= concentration of each PAH in sediment (µg/kg dry wt)
C
W= concentration of truly dissolved PAH in pore water (µg/L)
f
NPOC= weight fraction of non-pyrogenic organic carbon in sediment (kg non-
pyrogenic organic carbon/kg dry wt, calculated from the difference
between TOC and black carbon)
K
OC= organic carbon to water distribution coefficient (L/kg)
f
BC= weight fraction of black carbon in sediment
(kg black carbon/kg dry wt)
K
BC= black carbon to pore water partition coefficient (L/kg)
n = Freundlich exponent, which accounts for nonlinear sorption behavior
(n=0.6) (Accardi-Dey and Gscwend 2002)
An iterative approach was used to solve for C
W.C
Wfor each PAH is
divided by its corresponding FCV to calculate a toxic unit.

13. Relationship of log K
OWto log K
BC
Data from Accardi-Dey and Gschwend 2003

14. Station
TOC
(%)
BC
as %
of TOC
Lead
(mg/kg)
Total (34)
PAHs
(mg/kg)
Avg
Survival
(%)
Avg
Repro
(# offspring)
1 0.6 1.6 7.9 2.0 96 8.2
2 1.4 0.7 26 10 94 7.3
3 2.6 2.5 52 11 91 7.4
4 2.2 12.3 6400 662 78 2.4
5 2.3 2.4 1100 68 93 7.7
6 2 1.5 1900 114 84 2.8
7 2.7 4.5 2500 895 63 3.2
8 1.7 8.5 2600 150 83 4.5
9 3.2 2.4 2700 225 2 0
10 1.9 0.5 710 84 94 5.3
11 1.9 0.5 420 72 93 7.3
12 2.0 2.1 1200 57 10 1.0
13 1.4 17.8 340 48 90 6.3
14 2.0 2.3 240 101 92 4.7
Results of Physical Analyses for
the Brook Study Site
Significantly reduced survival = greenSignificantly reduced growth = yellow

15. Sum ESB Toxic Units for Modeled
and Measured PAH Concentration in
Porewater

16. Concentrations of PAHs in pore water measured by SPME were much
lower than predicted from the one-phase or two-phase model, which
could be influenced by the values of K
BCused in the 1-phase and
2-phase models.

17. Conclusions of SPME Analyses
•PAHs were ruled out as contributing to
observed toxicity
–ΣTU SPME indicates that PAHs would not
result in toxicity
–ΣTU for any method (one-phase, two-phase,
or SPME) did not correlate strongly with
survival and reproduction

18. Correlation Analysis
•Several metals, PAHs,
PCBs, and phthalates
were strongly
correlated with each
other and with survival
and reproduction
–Lead exceeded
probable effect
concentration (PEC)
to much greater extent;
lead PEC-hazard
quotient ranged from
2 to 50
•Target cleanup level
for lead set to 1,150
mg/kg
Numbers = Stations

19. Proposed Remediation Area

20. Summary and Conclusions
•Previous ERAs indicated that brook
sediments adjacent to the plant posed
an unacceptable ecological risk and
would need to be remediated
•Collecting site-specific data and using
innovative approaches in sediment
bioavailability provided more realistic
estimates of ecological risk and the
extent of remediation required in these
areas