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NEW ADVANCES IN PASSIVE SAMPLING FOR SEDIMENT RISK
ASSESSMENT
Upal GhoshDepartment of Chemical, Biochemical, & Environmental Engineering
UMBC
SETAC HDCOct 7, 2015
Legacy contaminants in exposed sediment contaminates the food chain through:
1) bioaccumulation in benthic organisms
2) flux into the water column, and uptake in the pelagic food web.
Contaminated sediment
1
Bioaccumulation of Hydrophobic Compounds
• Predictions work reasonably well for natural systems
• Predictions become more challenging for industrially impacted sediments
3
2 L water
100g fish
0.0002 mg DDD
1.7 mg DDD
Sediment1 ppm Koc = 151,000
Large fish1.7 ppm
Small fish0.5 ppm
Plankton0.0265 ppm
Water0.0001 ppm
Bioaccumulation And Exposure of DDD
Ehlers and Luthy, ES&T 2003
Measurement of HOCs in Water is Challenging
Need to measure <ng/L concentrations in sediment porewater
Two approaches to get to this concentration:
1) Modeling based on partitioning calculations:A) Sediment concentration and fraction OCB) Model presumes a certain partitioning behavior for the OCC) Complication from the presence of BCD) Difficult to characterize BC partitioning
2) Direct measurement:A) Detection limits associated with manageable grab samplingB) Separation of colloids challengingC) Passive sampling
Carbon Type Influences PAH Partitioning in MGP Sediments
• Red line shows predicted Koc based on NOM partitioning
• Measured Koc higher by two orders of magnitude
• PAH association with coal, coke, pitch, or soot increases observed Koc
Pyrene
4
5
6
7
8
HD
-3
HD
-5
HD
-6
NY
-5
NY
-18
TR
-12
TR
-15
Milw
auke
e H
arbo
r
Har
bor
Pt.
CA
-10
CA
-17
CA
-18
CA
-2
CA
-5
Me
as
ure
d lo
g(K
oc
)
7
Organic Carbon Types in Soil/Sediment• Sediment contains sand, silt, clays,
charcoal, wood, char, coal, & shells• PCBs/PAHs bound to carbonaceous
particles less bioavailable
charcoal
coal
sand
wood
shell
char
Petrography images
coal charcoal coke
0
1
2
3
4
5
6
7
activ
ated
carb
on
soot
carb
on
parti
culat
e co
al
parti
culat
e ch
arcoa
l
heav
y fue
l oil
coal
tar
Pula
kero
gen
colla
gen
hum
ic acid
degr
aded
alga
e
amor
phou
s org
anic m
atter
oxidi
zed
hum
ic acid
cutic
lealg
aelig
nin
cellu
lose
seve
ral s
oils a
nd se
dimen
t
log
(Koc
)
Phenanthrene partitioning for various organic materials
From: Ghosh et al. Environ. Sci. Technol. 2003
1) Hydrophobic chemicals partition among the aqueous and different solid phases
2) Equilibrium distribution can be described by: Freely dissolved
Passive sampler
DO
C
POCTwo approaches to measure total
and freely dissolved concentrations:
1) Remove POC by centrifugation, measure total dissolved concentration and DOC, estimate freely dissolved concentration.
2) Use calibrated passive sampler to measure freely dissolved concentration, measure DOC/POC, and estimate total dissolved concentration.
Conceptual Understanding of Passive Sampling:
Ctotal = Cfree + DOC*KDOC*Cfree + POC*KPOC*Cfree
PAH & PCB Uptake Kinetics in Well Mixed Batch
Hawthorne et al. Analytical Chem. 2009 & 2011
• Under well-mixed conditions POM, PE, or PDMS reaches close to equilibrium in <30 days
• Used to measure site-specific partition constants
10
Polymer Partition Constants
PDMSPAH: logKPDMS-w = 0.725logKow + 0.479 (R2 = 0.99)PCB: logKPDMS-w = 0.947logKow – 0.017 (R2 = 0.89)
POLYETHYLENEPAH: logKPE-w = 1.22logKow – 1.36 (R2 = 0.99)PCB: logKPE-w = 1.18logKow – 1.26 (R2 = 0.95)
POLYOXYMETHYLENEPAH: logKPOM-w = 0.839logKow + 0.314 (R2 = 0.97)PCB: logKPOM-w = 0.791logKow + 1.02 (R2 = 0.95)
• The most important parameter necessary for calibration is Kpw• Accurate measurement of Kpw for high Kow compounds is
challenging• A list of provisional Kpw values are available in Ghosh et al. 2014
Common polymers : Polyethylene (PE), Polyoxymethylene (POM) and Polydimethylsiloxane (PDMS)
11
• Practical guidance on the use of passive sampling methods (PSMs) for Cfree for improved exposure assessment of hydrophobic organic chemicals in sediments.
• Based on SETAC Technical Workshop “Guidance on Passive Sampling Methods to Improve Management of Contaminated Sediments,” 2012
Practical Guidance for Passive Sampling
Passive sampler uptake slow in static field deployments
12
𝑪𝒘=¿ ¿¿
Polymer-water partitioning coefficient
United States Environmental Protection Agency. (2012, Dec). Guidelines for using passive samplers to monitor organic contaminants at superfund sediment sites
Diffusive Process of HOCs Into Polymers
• First order mass transfer models=
13
CpKu Ke
CwCw
𝐾 𝑝𝑤 • A function of overall mass transfer coefficient
• Dissipation of Performance Reference Compounds
X
Cw Cw
Cp• Diffusion based models
(𝜀+𝜌 𝐾 𝑑)𝛿𝐶𝑤
𝛿𝑡=𝐷
𝛿2𝐶𝑤
𝛿𝑥2
Dp =Diffusion coefficient in polymer, ε = porosity, ρ = particle bulk density D = effective diffusion coefficient, Kd= sediment-water partitioning coefficient
14
Tracking pyrene diffusion with Fluorescence
PE/POM rod in Saturated Pyrene solution
Aluminum foil
Flu
ores
cen
ce in
ten
sity
Distance (mm)
Fluorescence image of polymer slice
Cut
0 1 2 3 4 5 6 70
2
4
6
f(x) = 0.660246633079289 x + 0.920257035396337R² = 0.997662762312603
Pyrene mass (pg)
Flu
ores
cen
ce i
nte
nsi
ty
15
Pyrene diffusion into PE (static)
Sediment side poly
mer
Performance Reference Compounds• Equilibrium slow for: 1) high Kow; 2) static porewater
• Mass transfer in sediment side difficult to predict
• Performance Reference Compounds (PRCs) are used to correct for non-equilibrium
• PRCs have similar diffusion properties as analytes
16
0 30 600
0.5
1
Analyte
PRC
Analyte ad-sorption
PRC des-orption
Pas
sive
sam
pler
Time (days)
Poly
mer
fracti
on
al
up
take
𝐶𝑝=𝐾 𝑝𝑤𝐶𝑤 [1 −𝑒𝑥𝑝 (−𝑘𝑒𝑡 ) ]
𝑘𝑒=−ln (𝐶𝑃𝑅𝐶 , 𝑓 /𝐶𝑃𝑅𝐶 ,𝑖)
𝑡
Limitations of PRC-correction methods• Low fractional loss of high molecular weight PRCs• Extrapolation from low molecular weight PRCs difficult:
17
Loss of low molecular weight
PRCs
Cfree High molecular weight
analytes
Adjustment methods
Inaccurate for high molecular weights
Diffusion model & Kd-Kow correlation2
1st order model & molar volume
correlation1
1- Booij, K.; Hoedemaker, J. R.; Bakker, J. F. Environ. Sci. Technol. 2003, 37 (18), 4213–42202-Fernandez, L. A., C. F. Harvey, and P. M. Gschwend, 2009a. Environmental Science & Technology, v. 43, p. 8888-8894.
How Do You Use Freely Dissolved Concentrations in Porewater (Cfree) ?
DO NOT: Call it : Bioavailable concentration or Bioavailable fraction
• Need a robust toxicity or biouptake model to plug in Cfree
• For PAHs: Can plug directly into toxic units calculation based on the narcosis model
• For other bioaccumulative compounds need to plug into a bioaccumulation model
Examples in last talk by Huan Xia
1) Ex-situ equilibrium measurements of sediment porewater
2) In-situ probing to assess ambient contaminant concentrations or to assess changes with time or with treatment
Pictures of typical applications:
sediment
water
Applications of Passive Sampling
Laboratory batch equilibrium
Field evaluation of treatment performance
Depth profiling of porewater conc. in sediment
Passive sampling of porewater and in-situ bioaccumulation
Tool for inserting passive sampler frame in sediment. The 8’ pole allows deployment from a boat in shallow water sediments
Passive sampler encased in stainless steel mesh and framed for sediment deployment
Underwater video camera for confirming placement depth
Rope and buoy for retrieval after deployment
Deployment Device For Inserting Passive Sampler Frame Into Surface Sediments
Image from underwater camera showing the passive sampler being inserted into sediment
0
20
40
60
80
100
120
1 10 100 1000 10000
Nontoxic Sediment
Toxic Sediment
Sediment Total PAH Concentration (mg/kg)
Perc
ent S
urvi
val (
%)
0
20
40
60
80
100
120
0.001 0.01 0.1 1 10 100
Nontoxic Sediment
Toxic Sediment
SPME Pore Water PAH Conc. (moles/L)
Sur
viva
l (%
)
NONTOXIC TOXIC
Figure 1. Chronic toxicity to H. azteca (28-day) can not be predicted from total PAH
concentration in MGP sediment
Figure 2. Chronic toxicity to H. azteca (28-day) can be predicted by estimating PAHs in
sediment pore water.
Prediction of Toxicity:Sediment vs. Freely Dissolved Conc.
Kreitinger et al , ETC 2007
Prediction of Biouptake in benthic organisms:Sediment vs. Freely Dissolved Conc.
• 7 freshwater and marine sediments• Freely dissolved conc. measured by passive sampling and also directly• Lipid concentrations better predicted from freely dissolved porewater
Werner et al. ES&T 2010
Predicted from sediment Predicted from porewater
Sediment
Passive samplers
Water flow in aquaria tanks
Components in each aquaria
• Treatments: Clean sediment (Rhode River)PCB impacted sediment (Near-shore Grasse River)PCB impacted sediment-AC treated in the lab
• Replicate aquaria with passive samplers in water column and sediment
• Fish species: Zebrafish• PCB-free diet• Sampling after 45 and 90 days
23
Prediction of PCB Uptake in Fish
Fadaei et al. ES&T 2015
24
Sediment Partitioning Coefficient Predictions
Schwarzenbach et al. 2003 Werner et al. 2009
25
• The total PCB concentration in fish was decreased by 87% after treatment with AC
PCB Residue in Zebrafish after 90 Days
Steady-State Approach
≈
Kinetic Approach
26
k1
k2ke
Predicting PCB Uptake in Fish
= - (+)
= (Arnot and Gobas 2004)
Observed and predicted PCB concentrations in fish
Equilibrium model Kinetic model with ingestion
ACKNOWLEDGMENTS
• Funding support from SERDP/ESTCP programs, NIEHS, USEPA GLNPO, and Alcoa
• Several students and post docs
KEY MESSAGES
• Freely dissolved concentrations of HOCs good predictor of biouptake and toxicity
• Passive samplers can accurately measure freely dissolved concentrations at equilibrium
• Corrections needed for non-equilibrium for in-situ measurements
30
Extraction Device
also containing a lipid source (sunflower oil) to mimic the lipophilic environment
Phase one: acidic gastric condition
Phase two: near-neutral intestinal condition
Simulated gastrointestinal fluid
CARBON TYPE ALSO INFLUENCES PAH BIOAVAILABILITY IN ANIMAL GUT
SERDP FUNDED STUDY
31
COMPARISON BETWEEN SOIL KD & BIOACCESSIBILITY
4 5 6 7 8 90.0
0.3
0.6
0.9
1.2
1.5
solvent spiked soil
Exponential (solvent spiked soil)
Benzo(a)pyrene
log KD
Bio
accessib
le F
rac-
tio
nn=30
BACKGROUND ON ESB GUIDANCE (2003, 2008)
• ESBs are based on a target lipid model (Di Toro et al. 2000)
• Developed critical lipid concentrations for 49 aquatic species
• 5th percentile expected to be protective of95 percent of species tested
Gen
us M
ean
Acut
e Va
lue
(mm
ol/g
oct
anol
)
Percentage Rank of Genera
TIERED ASSESSMENT
PAH AND PCB ABSORPTION EFFICIENCY IN CLAMS
From: McLeod et al. Environ. Sci. Technol. 2004
•Tracking 3H-BaP and 14C-2,2’,5,5’ PCB through a clam
ESB GUIDANCES (2008, 2005)