Oil in the ocean photooxidizes within hours to days, new study finds

Study provides new details on the fate of spilled oil in the marine environment, effectiveness of chemical dispersants


Research News


MIAMI–A new study lead by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science demonstrates that under realistic environmental conditions oil drifting in the ocean after the DWH oil spill photooxidized into persistent compounds within hours to days, instead over long periods of time as was thought during the 2010 Deepwater Horizon oil spill. This is the first model results to support the new paradigm of photooxidation that emerged from laboratory research.

After an oil spill, oil droplets on the ocean surface can be transformed by a weathering process known as photooxidation, which results in the degradation of crude oil from exposure to light and oxygen into new by-products over time. Tar, a by-product of this weathering process, can remain in coastal areas for decades after a spill. Despite the significant consequences of this weathering pathway, photooxidation was not taken into account in oil spill models or the oil budget calculations during the Deepwater Horizon spill.

The UM Rosenstiel School research team developed the first oil-spill model algorithm that tracks the dose of solar radiation oil droplets receive as they rise from the deep sea and are transported at the ocean surface. The authors found that the weathering of oil droplets by solar light occurred within hours to days, and that roughly 75 percent of the photooxidation during the Deepwater Horizon oil spill occurred on the same areas where chemical dispersants were sprayed from aircraft. Photooxidized oil is known to reduce the effectiveness of aerial dispersants.

“Understanding the timing and location of this weathering process is highly consequential. said Claire Paris, a UM Rosenstiel School faculty and senior author of the study. “It helps directing efforts and resources on fresh oil while avoiding stressing the environment with chemical dispersants on oil that cannot be dispersed.”

“Photooxidized compounds like tar persist longer in the environment, so modeling the likelihood of photooxidation is critically important not only for guiding first response decisions during an oil spill and restoration efforts afterwards, but it also needs to be taken into account on risk assessments before exploration activities” added Ana Carolina Vaz, assistant scientist at UM’s Cooperative Institute for Marine and Atmospheric Studies and lead author of the study.


The study, titled “A Coupled Lagrangian-Earth System Model for Predicting Oil Photooxidation,” was published online on Feb 19, 2021 in the journal Frontiers in Marine Science. The authors of the paper include: Ana Carolina Vaz, Claire Beatrix Paris and Robin Faillettaz.

The study was supported by the Gulf of Mexico Research Initiative (GoMRI): C-IMAGE III (Center for the Integrated Modeling and Analysis of the Gulf Ecosystem) and RECOVER 2 (Relationship of Effects of Cardiac Outcomes in ?sh for Validation of Ecological Risk).

From EurekAlert!

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March 12, 2021 10:33 pm

Oil must be continually oozing from natural vents under the oceans everywhere.
If it didn’t get broken down fairly quickly, there wouldn’t be a beach worth visiting anywhere.

Ron Long
Reply to  Mr.
March 13, 2021 1:25 am

Mr. is correct. During the late 1970’s I interacted with the CONOCO Research Lab in Ponca City, Oklahoma. They had developed an airborne UV laser system to illuminate oil from sea floor seeps, and it worked great for “prospecting” for new oil locations. Then they noticed that the passage of ships was easily detectable due to the lubrication products trailing after the ships and because these refined products fluoresced much stronger than unrefined seeps. The program was put under wraps by some one of the alphabet secret service groups of the US, as they realized they could also detect submarines with the technique.

Reply to  Ron Long
March 13, 2021 7:04 am

Ron, I spent decades detecting submarines with various equipment for sensing different emissions from subs. Never got to use that one.

Gordon A. Dressler
Reply to  mkelly
March 13, 2021 7:34 am

Likely because submarine engineers since the days of WWII realized that leaks of lubricating oil and diesel fuel from submarines were not favorable for vessel underwater survival, and therefore extended great efforts to minimize/eliminate such.

Of course, then and even today such leaks are not so much of concern for surface-going marine vessels since they are readily detectable day or night by means other than trailing oil slicks.

Reply to  Gordon A. Dressler
March 13, 2021 9:17 am

Gordon you are probably correct. Plus by the late 70’s the Russian sub fleet was primarily nuclear and only some of their allies had diesel subs.

Ron Long
Reply to  mkelly
March 13, 2021 4:59 pm

All of your comments notwithstanding, the airborne UV laser system, with accurate remote sensing screen, could literally see drops of oil in sea water, especially refined products.

Justin Burch
Reply to  Mr.
March 13, 2021 6:14 am

Oil not only continues to ooze but there is an entire ecosystem that runs on the degradation of it. During the oil spill there was a spill sized explosion of bacterial activity circulating with oil. That helped a lot. Unfortunately that bacteria does not work on beaches.

Reply to  Justin Burch
March 13, 2021 8:32 am

Where did you get the idea that bacteria does not help to break down oil on beaches?

Reply to  Mr.
March 13, 2021 8:30 am

There are beaches where you need to clean your feet after leaving them. But these beaches are few in number.
Interestingly enough, the number of beaches in S. California that had tarring problems dropped dramatically after they started drilling for oil near those beaches.

Reply to  MarkW
March 13, 2021 12:23 pm

These were from local, transient pressure sinks from production. The source of producing zone pressure support is the Pacific Ocean. The tarring will continue unabated now that the wells have mostly watered out, and the Cal offshore PAA pipeline system is so rotten that it can’t be economically resuscitated.

The twisted logic that minimizes the impacts of the ’69 and ’97 oil spills because “It’s always tarring out there” also continues unabated…

Reply to  bigoilbob
March 13, 2021 7:04 pm

The beach tarring in southern Cal is from production? You live in a fantasy world.

1% of the oil in the ocean there is from drilling. 4% is from oil transport. 33% is from oil consumption (ships, run-off from roads, etc). 62% is from natural oil seeps. Some of the largest natural oil seeps in the world are off the southern Cal coast.

The tarring will continue, reduced by a whopping 1% if production has been stopped. Or are you maintaining that nature only allows oil produced by humans to pollute beaches?

Reply to  jtom
March 13, 2021 7:52 pm

The beach tarring in southern Cal is from production?”

Reading comprehension, pro favor?

What I actually SAID was the that the offshore production resulted in a temporary REDUCTION in this tar production. When the production ceased (about 8 years ago, when the PAA pipeline finally burst a seam from lack of maintenance), tarring trended towards its historic average.

Bill Rocks
Reply to  Mr.
March 13, 2021 9:12 am

Correct. There are thousands of natural oil seeps in the deep water of the Gulf of Mexico as documented by Texas A&M Univ. and others a long time ago.

Reply to  Mr.
March 13, 2021 10:00 am

Opposition to oil and gas has nothing to do with pollution or the environment. It’s all about gaming the system so that the neo-oligarchs are enriched in the Green New Deal. The only math that matters is the math that fattens their bank accounts. If the world ran on renewables, the neo-oligarchs would invent oil and punish anyone who had the audacity to oppose it.

March 12, 2021 10:51 pm

Interesting research and thesis, but it may not be necessary.
All of the oil from the “Deepwater” disaster ended up in the Bermuda Triangle.
Never to be seen again.

Farmer Ch E retired
Reply to  Bob Hoye
March 13, 2021 3:32 am

As I recall, about half the DWH oil remained at depth because it was so finely atomized it was neutrally buoyant. It was then handily biodegraded.

Reply to  Farmer Ch E retired
March 13, 2021 8:33 am

If memory serves, I thought the oil on the surface came from the drill rig when it exploded.

Reply to  MarkW
March 13, 2021 10:38 am

Oh, no, Mark. I clearly recall all the efforts to close down the ruptured wellhead on the seafloor at the time. And I also recall a company that has a system to recover the oil slick from the surface, but the EPA and other Federal alphabet agencies refused to let them operate because their equipment was only about 95% effective, and they demanded 99+%.

So they allowed the oil slick to reach shore instead…

Reply to  Kpar
March 13, 2021 12:37 pm

“And I also recall a company that has a system to recover the oil slick from the surface, but the EPA and other Federal alphabet agencies refused to let them operate because their equipment was only about 95% effective, and they demanded 99+%.”

Versions of this story of a miracle company recur after every spill. Including the 2 in which I was part of the response team. And my bro’ a veteran EPA OSC often gets pimped by outfits trying to get him to use the next big thing. Or at least to get them on the list of approved vendors. A little due diligence on his part chases most of them away.

I have not seen any doc of this, but since I’m not a GOM guy, I might have missed it. Got anything beyond your “recollection?

Farmer Ch E retired
Reply to  Kpar
March 13, 2021 7:23 pm

Many technologies were employed but the ones I observed were mostly traditional involving sand screening, oil booms, sand washing plant, and good old fashioned land filling. I was an auditor on and off for a couple of years checking the work activities and waste handling against the regs and other documents. Here’s yours truly on one of the islands east of Grand Isle, LA.

March 12, 2021 11:11 pm

I have to ask: Did these kids bother to go play outside and see is what happened on their computer screens actually concurs with what happens in, say, a bucket of salt water? Or do they need a grant to go to a specific beach in the Rivieras?

Pamela Matlack-Klein
Reply to  paranoid goy
March 13, 2021 2:57 am

I would like to think today’s students at Miami did go out in the field, they can literally walk outside the building and mount an investigation in the harbor. Back in my day, BC (before computers) we lived for fieldwork and my happiest memories of grad school are of the assorted locations where I actually went and collected raw data.

March 12, 2021 11:12 pm

Typo in headline fixed.


Reply to  Willis Eschenbach
March 13, 2021 8:34 am

Ah shucks, where’s the fun in that?

March 13, 2021 12:27 am

Seems to be a case of a model generating data, not data generating a model. In other words “junk science”. Yawn, going back to sleep.

Peta of Newark
March 13, 2021 12:51 am

Under which rock are these people from…

Photooxidation of Crude Oils
Quote:””Publication Date:October 2, 1998
Copyright © 1998 American Chemical Society“”

Oil Weathering after the Deepwater Horizon Disaster Quote:””Publication Date:July 18, 2012

Stephen Skinner
March 13, 2021 2:33 am

Oil and coal are natural and organic and made from recycled dead plants and animals. 100% green.

Gordon A. Dressler
Reply to  Stephen Skinner
March 13, 2021 7:41 am

“100% green.”?

Au contraire . . . cannot be such if they can be burned to produce CO2 that would be released into the atmosphere. You have to understand the FULL meme. 😉

March 13, 2021 4:04 am

A local company here in Scotland attended the Exon Valdes grounding. They were appalled that the oil was to be removed from the beaches. They thought that there would be much less environmental damage overall if it was just left to break down naturally, although the animal and bird casualties might be greater to start with.

Nick Graves
Reply to  Oldseadog
March 13, 2021 5:15 am

IIRC, they used to love squirting detergent everywhere, but it transpired it merely washed the natural oils out of seabirds’ feathers and they drowned.

As well as k111-ing the rest of the flora & fauna.

Best to leave it to nature to resolve the mess.

Then again, some people think that things like catalytic converters are magical, when all they do is speed up a natural process.

Reply to  Oldseadog
March 13, 2021 7:17 am

This company has developed an organic solvent that is benign and does a great job on getting oil out of feathers without damaging the barbs, etc on the edges and is less stressful on the birds and mammals. They haven’t gotten to market yet but the research looks very promising. The solvent can be recycled indefinitely and works with salt water. It also can be used to capture the bitumens in oil sands.


Reply to  Oldseadog
March 13, 2021 8:37 am

I remember reading about an experiment that was run at the time. They isolated a small section of beach and spread some chemical that increased the number of bacteria. A month later, that section of beach was the cleanest section in all of the spill zone. With no environmental degradation.

John Savage
March 13, 2021 5:59 am

I have often wondered about the oil that was spilled during the Battle of the Atlantic. Thousands of merchant ships were sunk including many oil tankers. The stories of the day talk about the oil spills. But no one ever spoke about “environmental disaster” and I know of no account of long term damage. Anyone?

Reply to  John Savage
March 13, 2021 7:13 am

I suspect sometimes it burned of, because a torpedoed ship has a good chance of catching fire. There’s a scene in Das Boot (movie and, IIRC, the book) about that, and I recall being trained in the Navy for swimming away from a sinking ship while avoiding burning oil. Still, as you say, it wouldn’t all have burned. To this day, oil still leaks from the wreck of the USS Arizona in Pearl Harbor.

Reply to  John Savage
March 13, 2021 8:40 am

Does anyone know where the deep water that is flowing through the N. Atlantic is going to come back to the surface and when? I’ve wondered how all that rusting iron is going to impact the chemistry of that place.

Julian Flood
Reply to  John Savage
March 13, 2021 9:05 am

That’s why the blip.


H. D. Hoese
Reply to  John Savage
March 13, 2021 9:57 am

There were stories of oiled sailors on Louisiana beaches, refined materials often burned. One even torpedoed by accident a Mississippi River jetty.
Wiggins, M. 1995.Torpedoes in the Gulf. Galveston and the U-Boats, 1942-1943. Texas A & M Univ. Press.

Julian Flood
March 13, 2021 6:19 am

If you look at the bigger version of the DW spill on 30 April 2010 (it’s in a lower link picture below the post at https://wattsupwiththat.com/2010/04/30/nasa-satellite-tracking-the-gulf-oil-spill/) there is a large slightly darker area in the Gulf, extending over a much greater area than the obvious spill. Its edges are delineated in part by lines of cloud. The question is what causes that darker area?

My suggestion is that the lighter fractions of the spill have spread much more rapidly and are smoothing the surface, lowering the albedo slightly and thus showing up as darker.

Why are the clouds so sharply edged? What is the temperature of the surface in the darker area compared with the unpolluted surface?

I have seen a huge smoothed area in the Atlantic covering in a discontinuous fashion thousands of square miles from abeam Oporto to a couple of hundred miles short of Madeira. It was mostly broken into huge meandering rivers, but at times it formed complete cover, suppressing all wave breaking which was obvious in the non-smoothed areas where the wave action was consistent with a Force 4 breeze. . The difficulty is that there was no obvious source for the pollution unless it had travelled for weeks. So was it natural, underwater seeps (there’s a white smoker nearby), phytoplankton lipids, breakdown resistant pollution from the eastern seaboard? If it was any of those then it needs investigation — smoothed water has lower albedo so warms more readily and the lack of breaking waves reduces salt aerosol production and thus cooling stratocumulus.

I’ve seen smooths in rivers, the Med, the Atlantic and I believe they may involve surfactants as well as light oil. The first synthetic surfactant, Tide, was notoriously resistant to breakdown. Perhaps researchers Ana Carolina Vaz, Claire Beatrix Paris and Robin Faillettaz could look at modern surfactant/oil mixtures to see if degradation rates are the same.


Reply to  Julian Flood
March 14, 2021 9:18 am

IIRC, the surface-oil greatly reduced/stopped water evaporation and that may have an effect on clouds over that area.

Rich Davis
March 13, 2021 6:34 am

It’s from EurekAlert!, so first off, you know it’s BS.

The claim is that we need stricter regulations on offshore drilling to take into account this “new discovery” that solar radiation degrades oil rendering chemical dispersants ineffective.

In other words, they need a way to shut down rigs that already have permits. They are planning to make it cost so much that it’s not economically viable to drill offshore.

Then we’ll hear stories about how the cost of wind and solar being lower than oil and gas. It’s a familiar playbook.

March 13, 2021 6:37 am


Entirely natural, organic, made from plants and biodegradable.

What’s not to like?

Rich Davis
Reply to  ThinkingScientist
March 13, 2021 6:44 am

Yep, it’s downright vegan.

Please consider a vegan lifestyle—for the Planet. Burn all-natural, organically-grown fossil fuels.

H. D. Hoese
March 13, 2021 6:46 am

“The UM Rosenstiel School research team developed the first oil-spill model algorithm that tracks the dose of solar radiation oil droplets receive as they rise from the deep sea and are transported at the ocean surface.”

I’ll have to check but bet there is old chemical evidence about this. The spill came from a natural seep area known for over a century, lots ended up on Texas beaches after the more toxic volatiles disappeared leaving the tars. You can find hydrocarbons in mud, they have been researched since discovery. This is one my favorite quotes.

 “In terms of geologic pollution the Mississippi River was, and is, North America’s largest sewer system. It collects and dumps waste into the Gulf cesspool, where oil and gas forming processes start immediately.”

   Clark, R. H. and J. T. Rouse. 1971. A closed system for generation and entrapment of hydrocarbons in Cenozoic deltas, Louisiana. Bulletin American Association Petroleum Geologists. 55(8):1170-1178.

March 13, 2021 7:14 am

“It helps directing efforts and resources on fresh oil while avoiding stressing the environment with chemical dispersants on oil that cannot be dispersed.”

The cure is worst than the disease.

Gordon A. Dressler
March 13, 2021 7:23 am

From the above article: “After an oil spill, oil droplets on the ocean surface can be transformed by a weathering process known as photooxidation, which results in the degradation of crude oil from exposure to light and oxygen into new by-products over time.”

Um . . . how toxic might any of these “new by-products”—not delineated in the above article—be over time?

March 13, 2021 1:13 pm

Wow! Who would of thunk it. Another case of Mother Nature taking care of herself.
Or maybe of “Intelligent Design”.
OK, enough PC speak. God designed HIS creation to generally take care of the all the crappy things humans would do to it.

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