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Sat Jun 15, 2019, 12:20 AM

Elucidation of the Molecular Signatures of 2 Gulf of Mexico Oil Disasters by 2D GC/MS (GCXGC/MS)

The paper I'll discuss in this post is this one: Exploring the Complexity of Two Iconic Crude Oil Spills in the Gulf of Mexico (Ixtoc I and Deepwater Horizon) Using Comprehensive Two-Dimensional Gas Chromatography (GC × GC)

The Gulf of Mexico is being destroyed by two closely related forms of energy, the dangerous fossil fuel petroleum, and the dangerous form of so called "renewable energy," ethanol.

Because so called "renewable energy" has been absolutely ineffective at addressing climate change, the climate catastrophe is accelerating at the fastest rate ever seen, and to be sure, one effect has been the flooding of the American Midwest that took place in early spring, on highly fertilized corn and wheat fields. These floods are draining into the Mississippi carrying the fertilizer, phosphorous and fixed nitrogen into the Gulf of Mexico, where it causes heavy toxic blooms of algae that choke off the oxygen, killing fish, shrimp, oysters, crabs and the economic life of fishermen and fisherwomen. Because of this year's flooding, NOAA is predicting the largest ever Gulf of Mexico dead zone, close to 8,000 square miles of a completely dead region of the Gulf at the Mouth of the Mississippi.

Thank you Iowa caucuses.

Don't worry, be happy.

"Bioenergy," which is responsible for slightly less than half of the 7 million air pollution deaths that take place each year grew by 15.16 exajoules to 57.99 exajoules.

IEA 2017 World Energy Outlook, Table 2.2 page 79 (I have converted MTOE in the original table to the SI unit exajoules in this text.)

In this century, world energy demand grew by 164.83 exajoules to 584.95 exajoules.

In this century, the solar, wind, geothermal, and tidal energy on which people so cheerfully have bet the entire planetary atmosphere, stealing the future from all future generations, grew by 8.12 exajoules to 10.63 exajoules.

Probably even worse than so called "renewable energy," for cars, corn ethanol, however, are the oil disasters in the Gulf. In the 21st century, oil has been the second fastest growing source of energy (an increase of 30.23 exajoules to 185.68 exajoules) second only to coal (an increase of 60.25 exajoules to 157.01 exajoules).

The two major oil disasters of the last 40 years in the Gulf of Mexico (outside of climate change itself) are the Deepwater Horizon disaster and the Ixtoc 1 disaster.

From the text of the paper:

Large catastrophic oil spills capture the spotlight of the media, scientists, policymakers, and general public, demanding an effective and immediate response. One overarching tenet to oil spill science is that the type of spilled oil and its distinct chemical composition are critical to the response, damage assessment, and restoration efforts of impacted areas. With this understanding, a useful comparison of variable chemistries of large-scale oil spills provides a means to identify the spill source and disentangle the effects of biotic and abiotic weathering processes, local geography, and other critical factors, all of which contribute to our understanding on the fate and effects of accidental oil releases.

Two examples of such oil releases are the Ixtoc I and the Deepwater Horizon (DWH) blowouts, both occurring in the Gulf of Mexico (GoM). The Ixtoc I spill lasted from June 3, 1979 to March 23, 1980, releasing an estimated 3 000 000 barrels of crude into the southern GoM (lat: 19° 24′ 30.00″ N, lon: −92° 19′ 30.00″ W). The spilled product traveled along the Mexican coastline and also impacted the Texas coastline.1 Thirty years later on April 20, 2010 and lasting for 87 days, an estimated 5 000 000 barrels flowed from the damaged Macondo well, following the explosion of the DWH drilling rig (lat: 28° 44′ 11.86″ N, 88° 21′ 57.59″ W).2 Contrary to the DWH accident, the impacts of the Ixtoc I spill are far less understood due to limited post-spill research and monitoring efforts. In order to close this research gap, recent studies have identified areas in the southern GoM, where residues from the Ixtoc I spill continue to persist.3,4


Forty years after Ixtoc "residues...continue to persist."

(If you want to have some fun, you can try reading some "by 2020" predictions made in 1980 about how great so called "renewable energy" would be doing by now. Apparently the people of that time thought we'd be just all tooling around in our solar powered hydrogen HYPErcars by now.)

In terms of analytical chemistry science, the technique here is one that's been exploding quite a bit in recent years, 2D chromatography. A problem in chromatographic separations can be (and is) that closely related compounds can co-elute, that is obscure the presence of one another. Years ago, when I was a kid, 2D thin layer chromatography was a neat tool that was simple and easy to use. One would place a spot on a square TLC plate, elute with one solvent system, then flip the plate 90 degrees and elute with a second solvent system to separate any spots that actually contained more than one compound. In modern times, these same techniques have been applied to instrumental systems, 2D HPLC, and in this case, 2D gas chromatography.

The detectors here were high resolution time-of-flight mass spectrometers, with the mass spectrometer creating another degree of orthogonality to the analysis. The authors refer to this technique as GCXGC-HRT, rather than the more traditional GCXGC TOF terminology.

The authors are able to separate some very closely related compounds from the two oil spills, benzothiophenes, and using the differences in distribution, delineate which oil disaster is responsible for the destruction in particular areas of the Gulf.

Some pictures from the text:





Figure 1. Full GC × GC–FID plan view chromatograms of (a) Ixtoc I and (b) DWH crudes. In this figure the x-axis is the n-alkane carbon number retention index (21) and the y-axis is the second-dimension retention time in seconds. Elution fairways where examples of compound families, and elution positions in two-dimensional space are identified in panel (a).




Figure 2. GC × GC–HRT selected ion mountain plot chromatograms (m/z 184.034, 198.049, 212.065, and 226.081) highlighting the molecular ions of the suite of sulfur containing molecules known as dibenzothiophenes in (a) Ixtoc I and (b) DWH crudes. Both samples were prepared as 15 mg mL–1 hexane solutions, and 1 μL of each was injected on the GC × GC–HRT so that a visual comparison of dibenzothiophenes was apparent. Both chromatograms are scaled identically.



Figure 3. Plot of the RDBE vs carbon number for compounds containing sulfur hetero atoms detected in Ixtoc I crude oil, produced using a petroleomics application for LECO’s ChromaTOF software tailored for high resolution multidimensional GC × GC data. In this case, the PASHs were identified for compounds with RDBE values of 6, 9, 11, 12, and 14 (corresponding to benzothiophenes, dibenzothiophenes, phenanthrothiophenes, benzonaphthothiophenes, and chrysenothiophenes).




Figure 4. Plot of the RDBE vs carbon number for compounds containing nitrogen hetero atoms detected in Ixtoc I crude oil, produced using a petroleomics mass spectral data analysis application for LECO’s ChromaTOF software. In this case, nitrogen containing compounds were identified as condensed, polycyclic pyrrolic systems, such as carbazoles, RDBE 9, and benzocarbazoles, RDBE 12. All of the ions identified within the black dotted line oval are derived from carbazoles with an RDBE value of 9 (RDBE 10 & 11 data points are produced from fragment ions of RDBE 9 carbazole compounds).




Figure 5. GC × GC–FID plan view plot comparison of the diasterane/sterane and hopane biomarker region of (a) Ixtoc I and (b) DWH crude oils. This figure provides a visual comparison of the sterane and hopanoid biomarker molecules present in each sample. Here, the differences between both crude oils are most apparent. For example, the ratio of the DiaC27βα-20S diasterane peak and the peak labeled H (17α (H),21β (H) -hopane) is dramatically different in each crude oil. The NH (17α (H),21β (H)-30-norhopane ) to H (17α (H) ,21β (H) -hopane) ratio between the Ixtoc I and DWH samples is another easily visualized biomarker pair that can be used to distinguish these oils from one another. Lastly, note the compounds labeled de-A-cholestane, de-A-methylcholestane, and de-A-ethylcholestane in the Ixtoc I sample (blue print) are steranes in which the A ring of the sterane molecules have been cleaved open (presumably via biodegradation) and absence of these compounds in the DWH sample (mass spectra of the de-A-steranes are present in Figures S25–S27).



Figure 6. Graphical representation of potentially useful biomarker ratios for differentiating between Ixtoc I and DWH crude oils. A more extensive table of ratios can be found in Tables S9–S11.





Figure 7. Difference chromatogram produced with GC × GC–FID data that represent a comparison of two crude oil spills from the GoM. The base plane in this chromatogram appears white, compounds that are more abundant in the Ixtoc I crude appear blue, and compounds that are more abundant in the DWH crude appear red. This subtraction chromatogram was normalized by mass injection (1 μL of a 15 mg/mL solution in hexane) of each crude oil sample.



Pretty, isn't it?

The beauty of the science here, the wonderful advanced analytical techniques is somewhat marred by the results it shows. Is this not true?

From the conclusion:

This work showcases the resolving capacity of comprehensive two-dimensional GC for exhaustive characterization of volatile petroleum species, using the example of crude oils from two of the most iconic oil spills in the GoM; Ixtoc I, and DWH. Coupling a high-resolution mass detector is a substantial analytical improvement to GC × GC systems, which enables very granular identification of numerous alkylated homologue series, including within heteroatom containing compound classes, demonstrating a promising potential of GC × GC− HRT to become a complementary tool to typical petroleomics instrumentation such as FTICR-MS, for the studies of lower molecular weight, GC-amenable petroleum species. In addition, HRT data facilitated the identification of unusual de-A-sterane biomarkers, present in Ixtoc I crude. These novel analytical capabilities can be leveraged in multiple innovative ways to advance oil spill science: more robust spill source apportionment in complex systems with concurrent spill sources, such as the GoM; identification of molecular transformations occurring during crude oil weathering process, for improved predictive models of the long-term fate of persistent petroleum hydrocarbons in the environment; better toxicity assessments, in particular, because of more comprehensive characterization of highly alkylated and heteroatombearing species, which often have higher toxic potential than the parent compounds.33 More broadly, expansion of the analytical window and identification of novel molecular marker compounds will advance all the areas of organic (geo)- chemistry, for example, petroleum geochemistry as a field of research which will likely benefit from these types of highresolution analyses.


There are some questionable locutions here: The word "iconic" usually connotes a positive connection with an event; its etymology derives from "icon," a representation of something godly. While petroleum is regarded by some as god-like, it, um, really isn't, particularly when leaking into ecosystems. The other poor choice of words is the use of the word "biomarker" which usually refers to metabolic compounds in living systems, not in areas rendered dead by oil spills.

Anyway...

If unlike me, you're happy and not worried that all the "by 2050" blabber we're hearing in 2019 will pan out rather like all the "by 2020" blather in 1980, well, I really have nothing to say, since I feel I've already said everything I can say and am now reduced to repeating myself like a victim of auto-echolalia.

And so I repeat and repeat and repeat:

We clearly hate our children and our grandchildren and their grandchildren, because if we didn't, we wouldn't be blithely dumping responsibility on them to do precisely what we have been unable to do ourselves.

We're not doing anything to address our dependence on dangerous fossil fuels and in fact, couple them with the only real alternative to them, nuclear energy, in our emotional, if absurdly toxic, imaginations. We are so mindless that we think that the damage related to Fukushima is somehow worse than the annual destruction of the entire ecosystem of the Mississippi Delta region, and we allow events like Ixtoc and Deepwater to vanish down the the memory hole while continuing to worship our cars.

Nothing will happen "by 2050" because we are doing nothing now.

I trust you'll have a pleasant weekend.





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