danny reible – university of texas heidi blischke - gsi 1 polydimethyl siloxane 2 solid phase...
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PDMS1 SPME2 SAMPLING
Danny Reible – University of TexasHeidi Blischke - GSI
1 Polydimethyl siloxane2Solid Phase Microextraction
Solid Phase Microextraction (SPME) Sampler
A ) SPME Fiber Close - up
B ) Complete SPME Device
C ) Insertion into Sediment
Data Quality Objectives Determine whether exceedances of performance standards from
the record of decision and/or comparison criteria of more recent water quality criteria from EPA have occurred at any of the locations sampled. For this objective to be successful, low level detection limits for carcinogenic PAHs are necessary.
Assess concentration gradients between near surface and at depth. For this objective to be successful, samples from discrete intervals within the vertical sediment cap profile are required.
Define trends in interstitial water concentrations that may provide early warning signs of potentially significant contaminant migration through a cap (i.e. migration that may lead to exceedances of performance standards in the near future). For this objective to be successful, detection limits must be sufficiently low to detect PAHs to identify trends.
SPME Decision Logic
PAH< surface thresholdPAH> deep threshold PAH>thresholds
PAH< surface threshold
PAH<deep threshold
PAH> surface threshold PAH<deep threshold No Evidence of
Cap breakthrough
AWQS noncompliant. No Evidence of Bottom-Up breakthrough
Currently Compliant with AWQS
AWQS noncompliant. Evidence of Bottom-Up breakthrough
Fiber-Water Partition Coefficient
Average deviation <5%
Average deviation ~12%
y = 0.757x + 0.513R² = 0.970
3.0
3.5
4.0
4.5
5.0
5.5
6.0
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
Log K
fw
Log Kow
Log Kfw
0.839*LogKow+0.117
Linear (Log Kfw)
f fw pwC K C
Detection Limits,Linearity, and Coefficient of Variation
Kfw
Concentration
Magnification
r2
Linearity COV PDMS
PDMS MDL µg/L
*
PDMS MDL µg/L **
Naphthalene 78.5 0.1547 88.8% 0.3332 0.07207DBF 4027 0.985 10.0% 0.0123 0.00265
2-MNP 2591 0.9817 70.2% 0.0268 0.00580Fluorene 4227 0.9984 5.6% 0.0697 0.01508
Acenaphthene 3662 0.9996 14.1% 0.0315 0.00680Phenanthrene 10938 0.9973 1.3% 0.0076 0.00164
Anthracene 10810 0.998 18.1% 0.0075 0.00161Fluoranthene 30327 0.9985 9.9% 0.0025 0.00054
Pyrene 35394 0.9987 8.1% 0.0021 0.00046Chrysene 52898 0.9967 19.1% 0.00048 0.00010
Benz[a]anth 85097 0.9978 3.9% 0.00011 0.00002Benzo[b]fluoranthene 119712 0.9945 11.6% 0.00011 0.00002Benzo[k]fluoranthene 120458 0.9781 8.0% 0.00002 0.00000
Benzo[a]pyrene 122795 0.9755 5.8% 0.00005 0.00001Dibenz[a,h]anthracene 142042 0.9241 5.5% 0.00007 0.00001Benzo[ghi]perylene +
Indenopyrene 161013 0.9179 7.0% 0.00010 0.00002
Average w/o Naphthalenes 0.98279 9.1%+/-5%
Conventional Detection Limit 0.0118COV Conventional Analysis 10%+/-8%
* 3cm of 10 um layer on 210 um core**1 cm of 30 um layer on 1000um core
Pros: Lower detection
limits for CPAHs – well below NRWQC
Early warning of increasing concentrations
Cons: Naphthalenes have
higher detection limits
Detection limit function of hydrophobicity
Method MDL Comparison
Detection Limits in smaller fiber (not used at M&B)
Fall 2010 SPME Sampling
24 SPME passive samplers were installed: 2 surface water (background) locations 22 sediment cap monitoring locations
After 7 days of exposure, 23 samplers were retrieved: One sampler was lost (Location 4)
SPME Installation
SPME Installation and Depths Target sample depths:
6” below the top of the armoring layer 6” into the sand cap 12” into the sand cap
The actual sample depths varied slightly from the target depths.
Sample Processing Pre deployment
Fiber and sampler cleaning (solvent rinse) Fiber placement in sampler
Deployment Via divers except at shore Difficulty in achieving target depths in armored
area Retrieval after 1 week
Sectioned on site and placed into pre-filled autosampling vial
Shipped back to UT and analyzed directly
Deployment – 1 week Is it adequate?
Static Lab Expts Anacostia River
Slow Equilibrium? Low cap sorption
capacity Speed
Equilibrium? Tides Groundwater flow
PAH Kinetics in Bare Fiber
Time (d)
0 5 10 15 20
Fib
er
co
nc ( g
/L)
0
100
200
300
400
500
600Phe
Chrysene
B[b]F
B[a]P
Deployment – 1 week Is it adequate?
Estimation Performance Reference
Compounds Time Series Two different size fibers
Puget Sound data shown 7 days Tidal system but no
shoreline Nonsorbing cap
Method Uncertainties PDMS
Fiber-water partition coefficient (error ~ 10%)) Equilibrium
PRC or two size fibers (failed in first application to site) Experience suggests near equilibrium for low MW PAH but high
MW PAH may be underestimated Maximum underestimation ~factor of 2-3
Site specific kinetic evaluation is recommended or use of thin fibers
Conventional pore water sampling (Henry’s probe) Poor detection limits (often near criteria) Poor depth control Potential for solids resuspension and sampling artifacts Includes both dissolved and colloidally/particulate bound
contaminants
SPME most biologically relevant
R² = 0.8723
0
5
10
15
20
25
30
35
0.0 1.0 2.0 3.0 4.0
Tis
sue
Con
cent
ratio
n (u
g/kg
)
Pore Water Concentration (ng/L)
Pore Water Concentration (21 day SPME)
R² = 0.4422
0
5
10
15
20
25
30
35
0.0 100.0 200.0 300.0 400.0 500.0 600.0
Tis
sue
Con
cent
ratio
n (u
g/kg
)
Pore Water Concentration (ng/L)
PAH Tissue Correlation Concentration (Centrifugation)
R² = 0.7583
0
5
10
15
20
25
30
35
0.0 0.5 1.0 1.5 2.0
Tis
sue
Con
cent
ratio
n (u
g/kg
)
Pore Water Concentration (ng/L)
Pore Water Concentration (2 day SPME)
R² = 0.2703
0
5
10
15
20
25
30
35
0.0 5000.0 10000.0 15000.0 20000.0 25000.0 30000.0
Tis
sue
Con
cent
ratio
n (u
g/kg
)
Sediment Concentration (ug/kg OC)
OC Normalized Sediment Concentration
M&B 2010 Results Summary 35% of possible compound detects measured LPAHs were detected more frequently than other
PAHs Acenapthene and phenanthrene were detected in
all samples Only LPAHs were detected in the two background samples The three most hydrophobic compounds were not
detected in any samples (likely due to low mobility) Dibenz(a,h)anthracene Benzo(g,h,i)perylene Indeno(1,2,3-cd)pyrene
2010 Near Shore Vertical Profiles: Pyrene
Near shore vertical concentration profiles are fairly uniform.
Concentrations either stay the same or increase slightly with depth.
Possibly due to mixing caused by tidal fluctuations.
2010 Off Shore Vertical Profiles: Pyrene
Off shore vertical concentration profiles display greater gradients than near shore profiles.
Concentrations increase with depth.
Comparison- 2009 & 2010 SPME
Individual PAH concentrations were compared for Locations 5, 9, 12, and 16. All concentrations increased at Location 5. Locations 9 and 16 showed some concentrations
increasing and some decreasing Most concentrations decreased at Location 12.
y = 416.93x1.2574
R² = 0.9271
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
10
100
0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10
SPM
E 20
10
SPME 2009 (Location 5)
y = 0.01x0.5575
R² = 0.8391
1E-06
1E-05
0.0001
0.001
0.01
0.1
1
10
100
0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10
SPM
E 20
10
SPME 2009 (Location 12)
Summary of Results 2010
1E-08
0.0000001
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
10
0 5 10 15 20 25
Nor
mal
ized
pore
wat
er c
oncn
sample locations
Naphthalene
Fluorene
Anthracene
Fluoranthene
pyrene
chrysene
B[a]A
B[b]F
B[k]F
B[a]P
NRWQC
Comparison to NRWQC Only one exceedance: chrysene at location 5
about 12 inches into the sand portion of the cap 18-24 inches below sediment water interface. 0.035 µg/L (duplicate 0.005 µg/L)
Two other detections approached NRWQC at the deepest sample intervals: Benz(a)anthracene was 80% of the criterion at Location 5 Benz(a)anthracene was 60% of the criterion at Location
16 All other compound concentrations at all other
locations and depths were well below the NRWQC.
y = x
R² = 1
All Data Fity = 0.9353x0.9821
R² = 0.9691Interarmoring
y = 0.9795x0.9852
R² = 0.9742
6" Subarmoringy = 1.0331x0.9903
R² = 0.9739
12" Subarmoringy = 0.8512x0.9767
R² = 0.9611
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04
B sa
mpl
es P
AH c
once
ntra
tions
(ug/
L)
A samples PAH Concentrations (ug/L)
Comparison of Duplicates- All samplesIA data
6" Subarmoring
12" Subarmoring
Comparison of Adjacent Duplicates
Comparison of Adjacent Sites 5, 17
0.0001
0.001
0.01
0.1
1
10
100
0.0001 0.001 0.01 0.1 1
Site
5 u
g/L
Site 17 ug/L
-6 cm
-7 cm
-18 cm
parity
Site 5 ~100 times higher than adjacent site (local contamination)
Conclusions - 2010 Sampling 35% of possible compound detections
compared to less than 10% in conventional approaches 50%+ in preceding years suggesting general downward trend
LPAHs detected more frequently than LPAHs No comparison criteria exceeded in inter-armoring or 6
inches into sand cap One cPAH (chrysene) exceeded at 12 inches into sand cap
at Location 5 Few increases noted at 12 inches into sand cap in 2010
samples relative to 2009 – will get trend data in 5-year sampling events for early warning
Sediment cap is protective of surface water and functioning as designed
Conclusions: SPME versus Conventional Sampling for M&B Long-Term Monitoring
SPME Detection limits << criteria More detections from which to draw conclusions Higher spatial resolution (no dilution by
withdrawing excessing water volume) Eliminates particulate and colloidal artifacts Minimal sample processing 1 day placement, 1 day retrieval vs 1 week
conventional sampling requirement More biologically relevant indicator