Oil Detection Methods Miss Important Class of Chemicals

MTorrice writes "For decades, scientists studying oil spills have relied on the same analytical methods when tracking the movement of oil and assessing a spill's environmental impact. But these techniques miss an entire class of compounds that could account for about half of the total oil in some samples, according to research presented last week at the Gulf of Mexico Oil Spill & Ecosystem Science Conference, in New Orleans. These chemicals could explain the fate of some of the oil released in the 2010 Deepwater Horizon accident and other spills, the researchers say."

Comments

Gas chromatographs again...

[Antipater]

All right, according to the gas chromatograph, the missing oil compound is... love!? Who's been screwing with this thing?

Spoiler

[SuricouRaven]

The overlooked chemical class is oxidized compounds produced by the oil degrading after the leak, usually ignored because they are more difficult to measure than plain old hydrocarbons.

Re:Spoiler

[mapsjanhere]

Not really, but with enough oxygen in it they start decomposing at the temperature of vaporization, producing short chain material that the automatic sample analysis suppresses. If you manually evaluate the samples you can still see it. Problem is that you get highly operator dependent results, and that makes comparing samples difficult. Also, once you've started to oxidize the material, biodegradation isn't far behind. So it's not really an environmental problem but literally an academic one.

Re:Spoiler

[mapsjanhere]

Sure it's an exciting science problem to look at - what individual compounds are part of the degradation chain of oil in the environment, how do we analyze it, what's the distribution, and is any of it toxic to wildlife. Plenty a PhD thesis in there. But the journalistic description of "we're missing part of a spill", implying that we're underestimating a problem, isn't really there IMO. Standard analysis gives you the amount of unchanged oil still around, stuff that kills birds by gumming up feathers etc. The oxidized material is quickly going to become water soluble or at least miscible as surfactant, and while not pretty it's going to dilute away in short order.

Re:Spoiler

[AK Marc]

So would releasing tons of O2 under/in the affected area, bubbling up O2 and diffusing in the water cause more rapid decay of the oil? Would that make it easier or harder to clean up?

Re:Spoiler

[flyneye]

If you use a dowsing rod, you aren't likely to miss anything...

Re:Spoiler

[sFurbo]

So would releasing tons of O2 under/in the affected area, bubbling up O2 and diffusing in the water cause more rapid decay of the oil?

Yes

Would that make it easier or harder to clean up?

Yes

Or, to be less snarky, oxygen is important in degrading oil, and oxygen depletion makes the oil degrade much slower. And we don't really know how toxic these compounds are. They are more hydrophilic than hydrocarbons, so they are more rapidly taken up and more rapidly excreted by organisms.

Re:Spoiler

[AK Marc]

Or, to be less snarky, oxygen is important in degrading oil, and oxygen depletion makes the oil degrade much slower. And we don't really know how toxic these compounds are. They are more hydrophilic than hydrocarbons, so they are more rapidly taken up and more rapidly excreted by organisms.

So we don't know if oxygenating would help clean it up or make it worse until we figure out where the "missing" oil went.

Re:Spoiler

[sFurbo]

Worse, even when we figure out where it goes, we don't know how toxic those compounds are. But even that is getting ahead of ourselves, we don't even know how toxic the compounds in oil are. We know how toxic PAH's are, because they are the major component of soot. In oil, however, the amount of alkylated PAH is much higher, and we don't know how toxic they are. Today, we measure the total petroleum hydrocarbon and a few of the PAH's to estimate the severity of pollution, which is fine if you have spilled paraffin and soot, but is probably not a very good probe for the toxicity of crude oil.

Re:Spoiler

[AK Marc]

I'll just pretend it's not that bad and the government will take care of us. The alternative is too depressing.

Re:Spoiler

[sFurbo]

If it makes you feel better, I am working in a group that is trying to asses the toxicity of alkylated PAHs and their degradation products. Whether that should be comforting because we are doing something, or because I probably see the problem as larger than it is is left as an exercise to the reader ;-)

Oxidized stuff

[vlm]

Oxidized stuff is kind of vague, chemically speaking. I'd love to look at the real paper (as opposed to the journalist interpretation) but I can't gain access. Just spins. Donno if its a free paper or paywall time.

Organic compounds containing oxygen... well, its been 20 years but are they talking about organic acids or ketones or aldehydes or alcohols or some freaky epoxides (that would be a WTF for sure). Doesn't have to be exclusive could be any mix of course.

I'm not a petroleum engineer but I play one on /. After cooking a million years underground I would think any trapped O2 would turn into water and CO2 as opposed to halfway stuff, so this indicates bioavailability after it leaked out... in other words its already half eaten up.

Re:Oxidized stuff

[MTorrice]

They haven't identified specific compounds yet--sounds like that is next on their to-do list. The scientists definitely think the compounds arise after the oil spills out of the well and sits out in the sun for a bit. Basically you're right: They're talking about the end results of oil degradation. But the big question is what do these chemicals do to marine life. Are they toxic? Or do they just sit around and living things ignore them.

Re:Oxidized stuff

[fadethepolice]

I work at a company that cleans oil spills and water. Sent this to a PHD project manager. His reply was "Interesting". So there is probably something to this method. Since the measurement of the amount not specified by the Gas Chromatography was dissolved en masse out of the sand there is some likelihood that some non-oil contamination was also dissolved out, and some likelihood that some was missed. Whatever the difference or perhaps deviation that is detected in the future form the results of this experiment, a 50% difference is just too large for it not to be a significant finding.

Re:Oxidized stuff

[kelemvor4]

Works fine for me - and looks very interesting too.

Your current credentials do not allow retrieval of the full text.

Re:Oxidized stuff

[icebike]

They imply that some of these can kill fish embryos in closed bays and estuaries.

one study linked unidentified oil chemicals to a spike in fish embryo deaths in San Francisco Bay

Really? How do they know it wasn't just raw sewage, or industrial chemicals if they didn't even identify the chemical, or even prove it came from the oil spill?

However, it appears their real complaint is this:

Reddy says overlooking these chemicals could hinder spill research in several ways, including thwarting scientists’ attempts to account for what happens to oil after a spill. After the Deepwater Horizon spill, government and academic groups could only explain the fate of about 75% of the oil released into the Gulf of Mexico. The oxidized compounds could be a portion of this “missing” oil, Reddy says.

Its not that the oil is "missed", its just that the oil once degraded to the point that it is not oil anymore is hard for them to measure with current methods, so they can't figure out where it went.

The main point, is that the oil is gone, degraded, oxidized, etc. The most dangerous (to marine life) part of the spill is gone.
The extent to which it is gone serves as an indirect measure of what these guys are trying to measure.

They offer very little in the way of support for their assertion that these chemicals are harmful.

Re:Oxidized stuff

[icebike]

50% "missed" simply explains where the oil went, after it ceased being "oil".

Re:Oxidized stuff

[Anonymous Coward]

http://www.scribd.com/doc/123045313/Oil-Weathering-after-the-Deepwater-Horizon-Disaster-Led-to-the-Formation-of-Oxygenated-Residues

To answer your question, yes -- organic acids, ketones/aldehydes, and alcohols were identified in the weathered oil samples.

Basically, they sampled oil from various locations (surface slick, rocks, sand) for 18 months. Using radiocarbon dating of representative samples, they verified that the samples originated from petroleum (not recently synthesized). They also verified that the samples came from the Macondo prospect by checking certain compositional ratios; the few that did not were excluded from the study. They used GC-FID, TLC-FID, elemental analysis, and a two-dimensional GC-GC method to analyze the samples. They used some internal standardization methods to verify that the oxygenated hydrocarbons were formed from the original crude oil -- this wasn't a case of the hydrocarbons washing away and leaving behind only oxygenated compounds.

The authors conclude that biological (bacterial metabolism?) and photochemical (sunlight-induced) mechanisms convert a significant fraction of crude oil into recalcitrant oxygenated hydrocarbons. The oxygenated hydrocarbons come off the GC later because they stick to the column; this means that many routine assays miss the oxygenated hydrocarbons. In other words, previous data overestimate the rate at which crude oil disperses in the environment. This could be by design -- it depends on your point of view at which point a product from the environmental degradation of oil can still be meaningfully called "oil." The authors push back against this point because of the potential toxicity and environmental longevity of these compounds:

"Oxyhydrocarbons also have the potential to exhibit toxic effects. [...] Toxicity is often assumed to decrease during oil weathering. This is because bioavailability,which is a prerequisite for compounds to manifest toxic effect, usually negatively correlates with hydrophobicity, and because less hydrophobic saturated and aromatic compounds disappear during oil weathering. However, oxygenation of oil residues during natural weathering has been suggested to increase their hydrophobicity, potentially making these residues more bioavailable."

Re:Oxidized stuff

[MTorrice]

Really? How do they know it wasn't just raw sewage, or industrial chemicals if they didn't even identify the chemical, or even prove it came from the oil spill?

The PNAS paper that looked at the SF Bay spill ruled out sewage and other chemicals found in the Bay. They suggest sunlight transformed crude compounds into toxic ones. The PNAS paper is in front of a paywall, I believe: http://www.pnas.org/content/109/2/E51.full

Its not that the oil is "missed", its just that the oil once degraded to the point that it is not oil anymore is hard for them to measure with current methods, so they can't figure out where it went.

The main point, is that the oil is gone, degraded, oxidized, etc. The most dangerous (to marine life) part of the spill is gone.

But where degraded oil goes is a question scientists want to know, mainly because they don't fully understand what those compounds do to wild life. So even if the chemicals aren't the ones that originally spilled into the ocean, what they become is still of interest to researchers, because they know less about them.

Re:Oxidized stuff

[Anonymous Coward]

I can't stand this sort of myopic thinking. Human excrement is "gone" after you flush the toilet, but it still has potential effects depending on where it goes. Effects that are meaningful; the same type of effects that one would would worry about if we didn't have toilets. Dislike that ammoniac outhouse smell? Well it's certainly not the smell of urine or feces, so quit complaining!

It's still very meaningful to describe the hazardous oily residue which contaminates beaches and other habitats after an oil spill as "oil." That's because it looks like oil and harms like oil. The fact that it's not chemically identical to the crude oil which came from the well is the sort of semantic bullshit that an industry cheerleader would rely on to distract the public from legitimate concerns about environmental harm.

Re:Oxidized stuff

[NatasRevol]

" The most dangerous (to marine life) part of the spill is gone."

That's an unknown statement, and what the scientists are trying to figure out.

Re:Oxidized stuff

[Anonymous Coward]

Oil spill research has generally focused on saturated and aromatic compounds and overlooked oxyhydrocarbons. This study shows that oxyhydrocarbons can be a significant mass of weathered oil, and this pool of carbon should be included into mass balance considerations after oil spills. Oxyhydrocarbons are relatively persistent, potentially making them recalcitrant tracers that could be used to assess degrees and kinetics of weathering, or for oil spill forensics, especially at weathering stages when other traditionally used oil compounds are degraded.

Re:Oxidized stuff

[sFurbo]

From the abstract of the actual article:

The incorporation of oxygen into the oil’s hydrocarbons, which we refer to as oxyhydrocarbons, was confirmed from the detection of hydroxyl and carbonyl functional groups and the identification of long chain (C 10 - C32 ) carboxylic acids as well as alcohols. On the basis of the diagnostic ratios of alkanes and polycyclic aromatic hydrocarbons, and the context within which these samples were collected, we hypothesize that biodegradation and photooxidation share responsibility for the accumulation of oxygen in the oil residues.

Of concern

[Frontier Owner]

when they extracted the organic compounds from the sand, did they normalize this against untainted sand from the area? Sand is going to contain some organic compounds naturally from the various marine life. Does their tests differentiate between crude oil compounds and rotting whale blubber compounds or seagull droppings?

Re:Of concern

[reverseengineer]

They established the origin of the hydrocarbons by measuring the carbon-14/carbon-12 ratio. Organic compounds made by living things on the surface of the earth will have a small amount of carbon-14 incorporated. Just about all the carbon-14 that had been present in the oil will have decayed with no opportunity for replacement, Their results for their oil-soaked sand show ratios of a few tenths of a percent of the atmospheric value, making it it likely that the vast majority of the hydrocarbons present were from sources which had been dead for eons.

Also, they have profiles of the same oil taken at the source well, surface slicks, and contaminated sand. While the oil degrades with environmental exposure, there is clear similarity among the compositions of the samples. The supporting information gives a lot of details on the experimental methods.

Re:Of concern

[PPH]

OK, but some of the carbon in the soil in my back yard has been dead for eons. So its not atmospheric ratios they have to look at, its a control sample from the ground (beach, whatever).

Re:Of concern

[sFurbo]

The half-life of C-14 is 5730 years, and unless you have upwelling of very old deep sea water or an oil spill, organic matter exposed to the sun is not that old. Still, a clean beach sample would have been a nice blank sample to compare with.

Re:Of concern

[PPH]

organic matter exposed to the sun is not that old.

What does sunlight have to do with it? Carbon that has been buried in the soil decays from C14 to C12. There is no reaction path to convert it back to C14. C14 is produced in the upper atmosphere by a reaction between Nitrogen and cosmic rays at a known rate. Once atmospheric C14 is bound into living (or dead) material, there's no going back to C14.

So some of the carbon in the soil in my back yard may have been there since the last ice age (or before). Until it was exposed by erosion or a backhoe. Unless something alive eats it and aspirates it as CO2, it could be very old.

Re:Of concern

[sFurbo]

What does sunlight have to do with it?

Well, the atmosphere will do, I guess. Or, to be more specific, oxygen. My point was that, barring some very special circumstances, all organic C is in equilibrium with the atmosphere on at least a decade or century timescale. Unless your backyard was a bog or otherwise under water until very recently, I doubt very much of the carbon is old. If there is oxygen present, life will make carbon into CO2, and there is oxygen present in most soil, at least in some parts of the year.

Re:first post detection methods miss important cla

[flyneye]

You are correct, according to my records Anonymous Coward was first to receive a frosty piss ( with a twist of lime)

Re:limitations of GC

[sFurbo]

Your points are generally correct, but your test for the non-GC-able prtion is not accurate. Compounds with boiling points well above the temperature of the column can be eluted from GC by having a high enough phase ratio, or a high enough flow, or waiting for a long enough time. A boiling point of 450 degrees C is reached at around C-30 , and I have seen presentations of GC of alkanes up to C-60, in I think I have heard about GC of up to C-100. In that range, it becomes more a question of thermal stability, but anything present in oil will have experienced prolonged periods of elevated temperature, so nothing particularly thermally labile should be left. However, this does not go for the degradation products.