Natural Weathering of Petroleum and the Applicability of - - PowerPoint PPT Presentation

Natural Weathering of Petroleum and the Applicability of Bioremediation for Oil Spill Cleanup: The Exxon Valdez Experience

Ronald Atlas University of Louisville James R. Bragg Creative Petroleum Solutions LLC

• “Natural biodegradation is ultimately one of the

most important means by which oil is removed from the marine environment, especially the nonvolatile components of crude or refined petroleum.”

• “…

with enough time, microorganisms can eliminate many components of oil from the environment.”

U.S. Congress, Office of Technology Assessment, Bioremediation for Marine Oil Spills—Background Paper, OTA-BP-O-70 (Washington, DC: U.S. Government Printing Office, May 1991)

Biodegradation is an Important Process that Removes Oil from the Marine Environment

OH OH COOH C H3

• C-SCoA

O R-CH2

• CH2
• C-SCoA

O O R-CH CH-C-SCoA R-CH

• CH2
• C-SCoA

O OH R-C-CH2

• C-SCoA

O O CoASH R-C-SCoA O NAD + H++ NADH + H2 O FAD FADH2 Fatty acyl CoA Acetyl CoA TCA CO2 n-Alkane Alcohol + H2 O Aldehyde Fatty acid COOH CH3 OH OH OH Catechol COOH NH2 OH OH HOOC CH3 COOH CH3 OH COOH OH COOH OH OCH3 COOH OH COOH OH OH HO Protocatechuate Ring fission

Diverse Marine Microorganisms Utilize Various Hydrocarbon Biodegradation Pathways to Degrade the Compounds in Crude Oil

Hydrocarbons Microbe Microbe Microbe Microbe

Carbon dioxide + Water Salinity Temperature Fertilizer Polars

Oil Spill Bioremediation

Enhances Rates of Biodegradation (Does not change extent of degradation)

Key Factors Affecting Whether the Rate of Oil Biodegradation Can be Accelerated Sufficiently by Nutrient Addition to Justify Bioremediation

• Concentrations of naturally available nutrients

must be limiting the biodegradation rate

• Sufficient oxygen must be present
• For shorelines, oil residues must have sufficient

contact with flowing water to supply necessary nutrients and oxygen

• Benefits must outweigh risk that oil will cause

ecological harm—efficacy and safety must be demonstrated

Demonstrating Efficacy of Bioremediation

Laboratory Studies and Field Demonstrations

Assessing Oil Weathering & Biodegradation Mass ratio method

% loss of component X = [1- (Cx /Ccon )w (Cx /Ccon )s ] x 100 Where: Cx = Mass concentration of component X in oil Ccon = Mass concentration of conserved species in oil (e.g., hopane or stigmastane) w = weathered sample s = source or reference sample

Sequence of Hydrocarbon Biodegradation

• Alkanes

Degraded Most Rapidly

• Aromatics

are also Degraded.

• Polars are

Generally Recalcitrant

Increasing weathering; compositional changes with time; and loss

• f total

polynuclear aromatics

Exxon Valdez PAH Weathering Sequence

Rates of Biodegradation of PAHs were Dependent on Number of Rings in Field Test at KN135

20 40 60 80 100 20 40 60 80 100 % Depletion Total PAH % Depletiion of Alkylated Phenanthrene

C1-Phenanthrene C2-Phenanthrene C3-Phenanthrene C4-Phenanthrene

Depletion of Alkylated Phenanthrenes Follows Expected Biodegradation Trends from PWS Samples Collected from 2001-2008

The PAH Content Decreases due to Various Weathering Processes Including Biodegradation

Dispersants Increase Rate of Biodegradation by Increasing Oil/Water Interfacial Area

Extent of Biodegradation Time (days) Control Increasing Dispersion Dispersants

Bioremediation of Exxon Valdez Spill: Addition of Nitrogen Fertilizers Accelerated Rates of Hydrocarbon Biodegradation by Indigenous Bacteria

Fertilizer Addition Enhanced Rates of Biodegradation in Field Tests without Causing Toxicity to Fish or Eutrophication and Algal Blooms

Extent of Rate Enhancement was Related to the Ratio of Nitrogen to Biodegradable Oil in PWS Field Tests

Fertilizer Addition was Shown to be Safe

Extensive Testing Prior to, and During Field Application of Fertilizer to Ensure Environmental Safety

• Prescreening of all fertilizers in laboratory tests with

aquatic biota

− Upper safe limits for ammonia based on Ambient EPA Water Quality Criteria (9.8 ppm max, 1.5 ppm continuous at shoreline conditions) − Toxicity tests conducted by EPA and Exxon using Inipol fertilizer and various marine biota species

• 1990 PWS bioremediation test monitoring

– Nearshore water monitored for toxicity to sensitive marine species – Potential for algal growth stimulation measured by chlorophyll concentrations in water – Monitored for oil washout and persistence of 2-butoxyethanol in Inipol liquid fertilizer, including using caged mussels

• Full-scale field application monitored
• Ammonia at ten locations was well below EPA guidelines

Oxygen Concentrations Decreased in Pore Water Following Fertilizer Application but Not Totally Depleted

Changes in Bacterial Populations

Many Commercial Products were Proposed for use by Exxon: None Had Sufficient Scientific Efficacy Data to Warrant Use

Duck Feathers Oil Eating Bacterial Cultures Orange and Lemon Peels

Full Scale Bioremediation Using Fertilizer Addition was Applied Extensively in Prince William Sound From 1989 to 1991

Extent of Fertilizer Application in the Largest Use of Bioremediation

Nitrogen Applied in 1990 Nitrogen Applied in 1989

By 2001 NOAA Estimated that 99.6% of the Spilled Oil Was Gone from Prince William Sound -- Microbes and Other Weathering Processes Worked

Only a Few Sites with Subsurface Oil Remained in 2001

40 80 120 160 Segment

HOR MOR LOR OF

Oiled Sediment Volume in 2001 Estimated by NOAA* (m

3)

* J. Michel, et al., 2006

40 80 120 160 Segment

HOR MOR LOR OF

Oiled Sediment Volume in 2001 Estimated by NOAA* (m )

3

(

* J. Michel, et al., 2006

Oil with TPAH Depletion > 70% 13.5% of total pits No oil or TPAH < 500 ng/g sediment 83.6% of total pits (Background Levels) Oil with TPAH Depletion < 70% 2.9% of total pits Oil with TPAH Depletion > 70% 13.5% of total pits No oil or TPAH < 500 ng/g sediment 83.6% of total pits (Background Levels) Oil with TPAH Depletion < 70% 2.9% of total pits

Overview of Total PAH (TPAH) Depletion for 761 Pit Samples Dug During 2007-2008 Surveys Less than 3% of the 761 total pits examined in 2007-2008 had SSO residue that was less than 70% depleted of TPAH

10 20 30 40 50 60 70 80 90 100

3 M 2 M 1 M 0 M Elevation Above Mean Low Tide

Most of the SSO Found in Pits in 2007-2008 Surveys Was Highly Weathered, Especially Within the Biologically Important Lower Intertidal Zones (0 to 1 M Elevation)

% of Pits at Each Elevation With Total PAH Depletion < 70%

Elevation Total Pits Dug +3 meter 188 +2 meter 191 +1 meter 171 0 meter 163

8% 3% 1% 1%

= No oil (includes pits with TPAH <500 ng/g sed.) = Depletion > 70% = Depletion < 70% % %

88 76

57

94 73

67

98 90 77 83 82 90

10 m +3 m +2 m +1 m

94

SM006B

88 76

57

94 73

67

98 90 77 83 82 90

10 m +3 m +2 m +1 m +1 m

94

Distribution of TPAH depletion in 2007 for SM006B

Oil: % TPAH Depletion < 70% 5% Oil: % TPAH Depletion > 70% 23% No Oil 72%

% of Total Pits

Oil: % TPAH Depletion < 70% 5% Oil: % TPAH Depletion > 70% 23% No Oil 72%

% of Total Pits

(This site contained 44% of all HOR & MOR found by NOAA in 2001)

Depletion > 70%

76 64

Workers

Distribution of TPAH Depletion for SM005B

= No oil (includes pits with TPAH <500 ng/g sed.) = Depletion > 70% = Depletion < 70% % %

No Oil 96% Oil: % TPAH Depletion > 70% 2% Oil: % TPAH Depletion < 70% 2% % of Total Pits No Oil 96% Oil: % TPAH Depletion > 70% 2% Oil: % TPAH Depletion < 70% 2% % of Total Pits

Trench

No Oil 58% Oil: % TPAH Depletion < 70% 15% Oil: % TPAH Depletion > 70% 27%

Distribution of TPAH Depletion in 2007 for EL056C (Also Showing Site of Trench Dug in 2008)

NO OIL 58%

2 7 % 27% 15%

= No oil (includes pits with TPAH <500 ng/g sed.) = Depletion > 70% = Depletion < 70% % %

66 62

TRENCH

500 1000 1500 TPAH = 6000 ng/g sed. % depletion TPAH = 90.4% TPAH = 46800 ng/g sed. % depletion TPAH = 78.8% TPAH = 15200 ng/g sed. % depletion TPAH = 55.3% TPAH = 22500 ng/g sed. % depletion TPAH = 48.5% TPAH = 165 ng/g sed. 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500

91 cm

Oil lens

56 cm 0 cm 76 cm Depth below Surface Cobbles

Upper Oiled “fringe”

25 cm

Lower Oiled “Fringe”

PAH Concentration (mg/kg extract)

Pit Bottom

Total PAH Depletion in EL056C Vertical Trench

500 1000 1500 500 1000 1500 TPAH = 6000 ng/g sed. % depletion TPAH = 90.4% TPAH = 46800 ng/g sed. % depletion TPAH = 78.8% TPAH = 15200 ng/g sed. % depletion TPAH = 55.3% TPAH = 22500 ng/g sed. % depletion TPAH = 48.5% TPAH = 165 ng/g sed. 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500 500 1000 1500

91 cm

Less Degraded SSO

56 cm 0 cm 76 cm Depth below Surface Cobbles 25 cm PAH Concentration (mg/kg extract)

Pit Bottom

Vertical Trench at EL056C Clearly Demonstrates Sequestration of SSO Residue

No SSO Highly Degraded SSO

Oil Sequestered with fine sand/silt

Water velocity through higher conductivity sediment above sequestered oil is high Water velocity through oil is very low

The Only Reason Any Oil Remains is Because It is Sequestered Within Isolated Thin Layers Containing Fine Sand/Silt

Generalized Cross-Section Off Boulder/Cobble Shoreline

• Oil in marine environments is subject to natural

biodegradation

• Detailed chemical analyses are needed to

assess the extent of oil biodegradation and the efficacy of bioremediation

• The use of internal compounds s (e.g.C30-

hopane or C-29aaa20R ethylcholestane [C29- stigmastane) that are resistant to biodegradation is critical for assessing the extent of oil biodegradation following an oil spill

Summary

• One should not expect 100% removal of a

pollutant by bioremediation ─Even after almost all biodegradable hydrocarbons are consumed, up to 50% of the original oil mass may remain as inert polars which are removed by other weathering processes

• The process of biodegradation is relatively

slow

• Biodegradative

removal takes weeks to months to years compared to physical removal which takes hours to days

Summary

Summary

• Bioremediation is an effective means for

speeding up the rate of biodegradation

– effective for the treatment of petroleum pollutants in many, but not all, cases – Establishing limiting factors is critical for determining appropriate teatment – Applicability depends upon environment

While There Are Clear Difference Between the 1989 Exxon Valdez Alaskan Oil Spill and the 2010 Deepwater Horizon Gulf Oil Spill, There are Valuable Lessons About the Applicability

• f Bioremediation and What Microbial Oil Biodegradation Can

Accomplish that Apply to the Current Situation

Coastal Marshes of the Gulf Coast Threatened by Oil from the Deepwater Horizon Spill in 2010 Rocky Shorelines Heavily Oiled by Exxon Valdez Oil Spill in 1989

Extra Backup Slides

Bioremediation Index = % Loss Total PAH – 70%

Calculation of Bioremediation Index

y = 0.9103x R2 = 0.9161

20 40 60 80 100 20 40 60 80 100

% Loss TPAH by C29R- stigmastane % loss TPAH by sum chrysenes

(G)

Where:

• % loss of Total PAH is computed from ratio of (Total

PAH/conserved biomarker) in sample compared to same ratio in spilled EVOS oil

• C29R-Stigmastane was most stable biomarker

(F)

y = 0.9596x R2 = 0.977

20 40 60 80 100 20 40 60 80 100

% Loss TPAH by C29R- stigmastane

% Loss TPAH by C30-Hopane

Hopane Showed ~ 4% loss Sum Chrysenes Showed ~ 9% Loss

Why Use 70% for Bioremediation Index?

Depletion for 2003-2004 Prestige Oil Spill Bioremediation Test (Moreira Site)

• Studies have shown that
• nce lighter alkanes are

removed and 60-70% of Total PAH are depleted, adding nutrients above normal shoreline background levels does not affect rate of biodegradation

(Gallego et al., 2006)

Alkanes Lost

• Amoco Cadiz study

Ixtoc-1 study

Bioremediation Indices for 2007-2008 Samples With Sufficient SSO to Quantify

(all samples with TPAH > 500 ng/g sediment)

• Only 125 samples (16.4% of 761 total pits) had enough oil to

quantify TPAH depletion

• 82.4% of those samples had positive bioremediation indices
• Overall, this indicates very low bioremediation potential
• 3 0
• 2 0
• 1 0

1 0 2 0 3 0

1 7 1 3 1 9 2 5 3 1 3 7 4 3 4 9 5 5 6 1 6 7 7 3 7 9 8 5 9 1 9 7 1 0 3 1 0 9 1 1 5 1 2 1

g

Bioremediation Index Based on C29R-Stigmastane

Bioremediation Index by Sum chrysenes

• 30
• 20
• 10

10 20 30

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69

y y

Total samples = 89 Fraction < 70% = 38.2%

• B. NOAA 2001-2003 SCAT I, II, III

Total samples = 74 Fraction < 70% = 41.9%

• A. ExxonMobil Survey

Comparison of Bioremediation Indices Using Sum

• f Chrysenes as “Conserved” Marker for

2002 ExxonMobil and NOAA 2002-2003 Samples

10 20 30 40 50 60 70 80 90 100

3 M 2 M 1 M 0 M Elevation Above Mean Low Tide

Most of the SSO Found in Pits in 2007-2008 Surveys Was Highly Weathered, Especially Within the Biologically Important Lower Intertidal Zones (0 to 1 M Elevation)

% of Total Pits with Total PAH Depletion < 70%

Elevation Total Pits Dug +3 meter 188 +2 meter 191 +1 meter 171 0 meter 163

2.0% 0.7% 0.1% 0.1%