Post on 01-Jan-2016
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Mesocosm Scale Evaluation of Dispersant Effectiveness and Toxicity
Kenneth Lee, Kats Haya, Les Burridge, Simon Courtenay, Zhengkai Li
Fisheries and Oceans Canada
Peter Hodson
Queens University
Michel C. Boufadel
Temple University
Albert D. Venosa
US Environmental Protection Agency
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Rational• For ecological relevance, the replication of natural sea-state
conditions and knowledge of environmental factors is essential for oil dispersant studies.
• National Research Council (NRC) Committee on Understanding Oil Spill Dispersants: Efficacy and Effects (2005) identified three factors to be addressed in oil dispersant efficacy studies:• Energy Dissipation Rate• Particle Size Distribution• Toxicity
• To address these specific issues, a wave tank facility was constructed at the Bedford Institute of Oceanography, Nova Scotia Canada
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Wave Conditions
(a) (b)
(c)
(a)Regular Non-breaking
(b)Spilling Breaking
(c) Plunging Breaking
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Factorial Experimental Designfor Dispersant Effectiveness Evaluation
• Factors:• Dispersants: Water (control), Corexit 9500, SPC 1000 • Waves: regular non-breaking wave, spilling breaker, plunging
breaker • Oil types: Mediun South American (MESA), Alaska North
Slope (ANS)
• Effectiveness indicators: • Oil concentration • Droplet size distribution
• Analytical methods• Ultraviolet Spetrophotometry • Ultraviolet Fluorometry• Laser In-Situ Scattering and Transiometry• Epi-fuorescent microscopy
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Sampling Locations
125
3200
Wave absorbers Flap-type wave maker
200
8000200
7070
5
200400020001500
Locations for UVS samplers Locations for laser particle counter
Dimension in cm; not to scale
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0 5 10 15 20 25 30 35 40 45
Depth below water surface, cm
10 -3
10 -2
10 -1
10 0
10 1
10 2
10 3
10 4
Ep
silo
n, m
W/k
g
Energy Dissipation Rate for Spilling, Plunging, and RegularWaves as a Function of Depth Below Water Surface
Plunger
Spiller
Regular
Energy Dissipation Rates
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49.025.0
1.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
29.015.0
1.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
5.03.0
1.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
19.010.0
1.0
Distance (m)
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
Water-MESA-Regular
5 min
30 min
60 min
120 min
Physical Dispersion
1.0
3.0
5.0
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
2.5
2.01.5
1.0
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
4.03.0
2.0
5.0
10 12 14 16 18 20D
ep
th (
cm)
-140
-105
-70
-35
3.0
2.0
4.0
Distance (m)
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
Water-MESA-Plunging
5 min
30 min
60 min
120 min
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Chemical Dispersion
25.01.0
73.049.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
11.0
6.0
16.0
1.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
5.0
9.0
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
5.0
7.5
Distance (m)
10 12 14 16 18 20
Dep
th (
cm)
-140
-105
-70
-35
Corexit-MESA-Regular
5 min
30 min
60 min
120 min
10.0
1.0
28.0
19.0
37.010.0
10.01.0
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
11.00
8.00
5.00
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
9.006.00
10 12 14 16 18 20D
ep
th (
cm)
-140
-105
-70
-35
6.005.00
Distance (m)
10 12 14 16 18 20
De
pth
(cm
)
-140
-105
-70
-35
Corexit-MESA-Plunging
5 min
30 min
60 min
120 min
9Droplet size (m)
10 100
Con
cent
ratio
n of
oil
(l/l
)
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
Droplet size (m)
10 100
Con
cent
ratio
n of
oil
(l/l
)
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
Con
cent
ratio
n of
oil
(l/l
)
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
Con
cent
ratio
n of
oil
(l/l
)0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
RegularWater
RegularCorexit
SpillingCorexit
Spilling Water
Plunging Water
Plunging Corexit
Con
cent
ratio
n of
oil
(l/l
)
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
Con
cent
ratio
n of
oil
(l/l
)
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
frac
tion
0.00
0.25
0.50
0.75
1.00
Droplet Size Distribution
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Dispersant Effectiveness of ANS
Wave Conditions
Regular non-breaker Spilling breaker Plunging breaker
Dis
pers
ion
Eff
icac
y (%
)
0
20
40
60
80
100
Water Corexit SPC
• Higher levels of chemical DE was observed for Corexit 9500 at the two high ε
• High DE was also achieved for SPC1000 at high ε
• Fresh ANS appears to be more readily dispersible than the weathered MESA crude,
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• Chemical dispersion has DE significantly higher than physical dispersion
• Spilling and plunging breakers increased dispersant effectiveness
Dispersion kinetics data demonstrate the change of the dispersed oil droplet size distribution as a function of time Corexit 9500 dispersed MESA and ANS to <70 μm at high ε at t=3min, and to <50 μm at 2 h at all three ε SPC 1000 needs higher ε to disperse MESA than ANS to smaller droplets
• The droplet size distribution of chemically dispersed oil has a larger number of small droplets (less than 10 um) compared to the
physically dispersed oil droplets.
Dispersant Effectiveness
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Toxicity
• Despite test results that show effective dispersion at sea, authorization and guidance for the use of these products is suppressed by concerns over biological effects on commercial species of fish from exposure to low concentrations of oil
• A key recommendation of National Research Council of the National Academy of Science was “Quantitative assessment of toxicological impacts from dispersed oil in the water column”
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System Modification for Continuous Flow Studies
• A “flow-through” system will allow simulation of natural exposure levels that result from dilution of dispersed oil in an open environment influenced by both tides and currents
• Operation in a flow-through mode will provide a controlled environment to study: Dissolution and uptake kinetics of toxic components as a function of oil
type and environmental conditions (including influence of SPM) The influence of exposure time and wave- and current-driven
hydrodynamic regime with mixture and dilution Environmental persistence (biodegradation of dispersed oil)
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Flow-through Wave Tank Facilities
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Mode of Action
• Toxicity of oils to fish is correlated to the concentration of alkyl-substituted-polynuclear aromatic hydrocarbons (PAH) in the water accommodated fraction (WAF) of oil
• Low molecular weight (LMW) hydrocarbons, such as BTEX, napthalenes, and C1-C12 aliphatics are acutely toxic by narcosis, they do not contribute to chronic toxicity because they are highly volatile and readily diluted in water
• High molecular weight (HMW) hydrocarbons such as waxes, resins and asphaltenes, are too large to be accumulated to toxic concentrations
• Difference in toxicity between WAF and CEWAF is likely due to the effect of dispersion on the solubilization of oil.
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2008 – 2009 Objectives• Compare the biological responses of selective marine
organisms to environmentally relevant time of exposure and concentrations of dispersed and non-dispersed oil
• The sequence of tasks will be: • lethality tests (acute toxicity tests - LC50)• Sublethal dose response tests• Identification of sensitive endpoints based on
relevant exposure times
The information generated will improve the capacity of The information generated will improve the capacity of on site spill managers to gauge the risks associated with on site spill managers to gauge the risks associated with dispersant applications and contribute to optimal control dispersant applications and contribute to optimal control strategiesstrategies
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Test Species
• Multi-endpoint toxicity analysis on commercially important marine finfish:
• Atlantic salmon smolts (Salmo salar)• Juvenile cod (Gadus morhua)
• Evaluate the toxicity of dispersed oil to function of developmental stage, exposure time, and dispersed oil concentration.
• Atlantic herring embryos (Clupea harengus)• The results will define the critical exposure windows
for the greatest and least toxicity, and provide statistical models describing the relationship between exposure time and concentrations of dispersed oil causing lethal and sublethal effects
• Shrimp (Pandalus sp. or Crangon sp.) depending on availability from local live harvesting in winter) will be used as a sensitive indicator of invertebrates in the acute lethality tests
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Toxicity EndpointsBiomarker Organ Comment
Cytochrome P-450 monoxygenase (MFO)
liver, gill Induced by polyaromatic hydrocarbons
Na, K - Adenosine triphosphatase
gill Osmoregulatory enzyme
Vitellogenin plasma Endocrine function - reproduction
Heat Shock Proteins liver General stress response
Glycogen Liver, muscle Indicator of metabolic reserves (energy status)
Total Lipid Whole body Indicator of metabolic reserves (energy status)
Hepato Somatic Index
Liver Hypertrophy induced by oil