9. Marine Oil Spills Flashcards
Are there natural seeps of oil into the ocean?
Yes, approx 5 x 10^6 tonnes every year
Benefit of natural oil seeps into the ocean
Since it is natural, there exists bacteria that have adapted to use hydrocarbons as a resource/energy
What are the two types of ocean hydrocarbon cycles?
- Short term hydrocarbon cycle
- Long term hydrocarbon cycle
Short term hydrocarbon cycle in the ocean (4 points)
- Cyanobacteria converts CO2 into alkenes (hydrocarbons)
- Bacteria converts hydrocarbons back into CO2
- Cyanobacteria uses CO2 for photosynthesis and convert it into alkenes
- Occurs over days
Long term hydrocarbon cycle in the ocean
- Hydrocarbons from natural oil formations seep up the water column
- Bacteria metabolize the hydrocarbons creating CO2
- Occurs over thousands to millions of years
What is Alcanivorax borkumensis? (4 points)
- It is the obligate hydrocarbonoclastic bacterium
- Meaning, hydrocarbons are the only thing they can use as a food source
- It plays a significant role in the biological removal of petroleum hydrocarbons from polluted oceans
- It produces natural emulsifiers (ex soap)
What are the steps of the fate of oil spilled form a tanker at sea? (10)
- Oil spills
- Oil slick reaches the shore
- Wash oil back into the sea
- Removal or addition of fertilizer
- Sedimentation by adsoroption to particulates
- Some volatilizes
- Some becomes water-soluble components
- Mousse formation
- Wave actions dirupts oil slick
- Biodegradation in water (soluble what descends from disrupted mousse)
What are some remediation treatment options for marine oil spills? (11)
- Evaporation / Aerosolization
- Physical recovery
- In-situ burning
- Dispersants
- Photooxidation
- Emulsification
- Dispersion
- Dissolution
- Oil particle aggregation
- Biodegradation
- Sedimentation
Exxon valdez spill, what treatments did they use? (5)
- Physical recovery
- Physical washing of shorelines
- Dispersants (Corexit)
- Burning
- First use of bioremediation (fertilizer) (only limited use)
What are the two major necessary steps when attempting to maximze the cleaning of a beach covered with crude oil?
- Clean up the bulk of the oil by physical means
- Clean up the remaining oil via in situ bioremediation
The in situ bioremediation was only done as a limited trial for Exxon Valdez
Braer spill VS Exxon Valdez spill: which had a bigger spill?
Braer
Braer spill VS Exxon Valdez spill: which took longer to remediate?
Exxon Valdex
* EV had heavier crude oil and calmer seas, whereas Braer had lighter crude and stormy seas
Braer
What compounds were added to stimulate biodegradation of crude oil on beaches
- Inipol EAP 22
- surfactant, contained N, P and C
- Customblen
- N & P
Braer
Were any microbes added?
No, the natural population was stimulated
How do you know if a bioremediation approach was successful? (3)
- Quantify residual oil contamination per area and by type of hydrocarbon, over time
- Look for enhanced population of hydrocarbon degraders at treated sites using molecular genetic methods
- Expect to find increased rate of biodegradation of crude oil constituents in sediments isolated from treated compared to untreated areas
Testing of Exxon Valdez Oil Spill results (2)
- Found signidifcant proption of total population were hydrocarbon degraders VS marine heterotrophs
- Found presence of 2 genes known to be important for biodegradation of hydrocarbons
* xylE → this gene encodes catechol 2,3-dioxigenase
* alkB → this gene encodes alkane monooxygenase
How to test the biodegradation rate? (4)
- Mix equal quantities of sediment slurry from treated (T) and reference (R = untreated, control) areas with 14C-labeled hexadecane or phenanthrene in test bottles (microcosms)
- Hexadecane is a n-C16 straight chain alkane often used as a model alkane in biodegradation studies
- Phenanthrene is a 3-ring PAH often used as a model PAH in biodegradation studies
- Compare the rate of 14CO2 produced over time and in T and R sediments
Exxon Valdex VS BP Deepwater Horizon
Largest spill
Deepwater Horizon (779 million litres VS 41.6 million litres)
Exxon Valdex VS BP Deepwater Horizon
What was the cause?
- Exxon: Tanker spill
- Deepwater: Well leak
Exxon Valdex VS BP Deepwater Horizon
Where was the spill when it was discharged? (depth wise)
- Exxon: discharged as a surface spill
- Deepwater: discharged at well head in 1500m of seawater
Exxon Valdex VS BP Deepwater Horizon
Where was the spill relative to the shore?
- Exxon: on Bligh (near island shorelines
- Deepwater: 77km offshore
Exxon Valdex VS BP Deepwater Horizon
Which used bioremediation extensively?
Exxon Valdez
Exxon Valdex VS BP Deepwater Horizon
Which used aerial and subsurface dispersants?
Deepwater Horizon
BP Deepwater Horizon
What remediation was used? (4)
- Evaporation
- Dispersant
- Burning
- Skimming : ships picking up oil
What is the issue with Corexit (the dispersant used in the BP Deepwater horizon spill)?
We are now more worried about the toxicity of corextit than the hydrocarbons in the gulf of mexico
Metagenomics
Sequencing of all the DNA from a polluted environmental sample and then looking for biodegradative genes and pathways of interest
Metatranscriptomics
- Isolate all mRNAs from an environmental sample, convert to complementary DNA (cDNA), sequence, compare to metagenome
- Indicates which genes are being transcribed ie coming from active microorganisms!
Metaproteomics
- Isolate all proteins from an environmental sample, sequence, compare to metagenome
- Indicates which genes are being transcribed / translated, i.e., really active!
Why does are plastic pollution problem need to be adressed quickly?
- Because plastics don’t biodegrade very well, since they are very long chains or big molecules that cannot fit in the catalytic sites of enzymes
- Because of the current rate at which we pollutle plastic
Can plastic be biodegraded at all?
Yes
* Plastic gets degraded into smaller and smaller pieces
* But it is difficult to mineralize it all the way to CO2 and water bc of its long chains
How is plastic biodegraded? (5)
- Initial attachtment of microbes on the plastic surface
- Microbial Biofilm formation
- Biodeteoriation: secretion of extracellular enzymes and EPS
- Biofragmentation: formation of oligomers, dimers, monomers (smaller bits of plastic)
- Last step would be mineralization to CO2 and H2O, but this seems to not be happening or only happening at the slowest rate ever
What provides a point of attack for hydrolytic enzymes to degrade plastic?
The presence of an ester bond (C-O)
What are examples (2) of a enzyme that can degrade plastic polymers?
Cutinases and lipases
What are the different types of plastics and to what degree are they degradable?
- Oil-derived, non bioddegradable polymers
- Oil based,biodegradable
- Bio-based biodegradable → can be completely mineralized
What is necessary for degradation of plastics?
Hydrolyzable bonds
What is the current “economy” of the plastic industry?
It is a linear economy of ‘take, make and dispose’ with limited recycling
What should the plastic “economy” be turned into?
- A circular production cycle where plastics are re-used, recycled and upcycled through their conversion to valuable products such as biodegradable polymers
- Introducing biodegradable plastics to this model through the upcycling of waste would allow the return of the carbon to nature in a managed, safe, and sustainable way
