Editor's Note: A team of researchers led by John Kessler, Texas A&M College of Geosciences chief scientist and assistant oceanography professor, traveled to the Deepwater Horizon disaster area to study the methane leaking into the Gulf of Mexico (along with tens thousands of barrels of crude oil) daily at the site of the damaged Macondo 252 well. Kessler, along with David Valentine (a professor of marine sediment geochemistry, biogeochemistry and geomicrobiology at the University of California, Santa Barbara) and the rest of his colleagues were hoping to come away with a rough estimate of the spill's size by the time his team returned home on June 20, followed by more accurate estimates as they complete their analysis of the information collected. Other objectives of the expedition onboard the RV Cape Hatteras included trying to determine how the methane might be removed from the water (whether eaten by waterborne microorganisms or released into the atmosphere) and how methane concentrations will change over time. The following dispatch was written by Valentine and Texas A&M Ph.D. graduate student Eric Chan. This is the team's fifth blog post overall for Scientific American.
Friday, June 18, 2010
By David Valentine, professor of marine sediment geochemistry, biogeochemistry and geomicrobiology at the University of California, Santa Barbara:
A wise professor once told me that as an oceanographer you should test all your tools and techniques thoroughly before you go to sea. But in the face of this oily disaster and the unique opportunity it provides for understanding how our world operates, this has not been possible. I would argue that improvising and adapting to the incoming data are equally as valuable in these instances. As a chemical oceanographer, modern tools and equipment are making this ever more possible. The examples I have been most impressed with on this cruise are devices to measure the abundance of stable isotopes in methane and carbon dioxide using cavity ring-down spectroscopy (CRDS).
The chief scientist, John Kessler, brought several Picarro instruments to analyze water and air samples in near real-time at high frequency. We have found another "off-label" use for these tools in tracking the rate at which microbes consume hydrocarbon gases. By feeding fresh samples of hydrocarbon-laden water with small amounts of gas containing an elevated amount of stable isotopes, we are now able to track the consumption of select hydrocarbon gases into their natural product, carbon dioxide—and we can do it aboard the ship. Previously, this would have required a bulky and temperamental mass spectrometer back on land.
The advantage of gaining this knowledge ship-board is that we've been able to develop and optimize techniques while at sea, which on this cruise has allowed us to track the respiration rates on hydrocarbon gases in a way that simply could not be done otherwise. Furthermore, this knowledge is helping us to design experiments to label the responsible bacteria with stable isotopes, which will enable their identification and study after the cruise.
Now back to the day at hand. Earlier this morning we were faced with an interesting situation; we had just arrived at our first morning site and were preparing to lower the CTD [conductivity, temperature and depth instrument] into the water when another vessel pulled along side and politely informed us they were initiating a controlled burn and suggested we ought move our vessel. Research boats are sluggish beasts by nature, and they never move as fast as impatient scientists would like, but it felt like we accelerated a bit faster than normal as the sea surface was lit afire and billows of black smoke ascended to the atmosphere above (see inset picture). Ever since we arrived we have seen the controlled burns from a distance, characterized by the thick plumes of dark smoke, and often by a cloud trail presumably caused by excess condensation nuclei. This was the first time I have seen the surface ablaze from so close, and was again provided a reminder of just how serious this spill is for the ecosystem, the ocean and the people of the Gulf States.
Image of controlled burn courtesy of David Valentine, University of California at Santa Barbara
Friday, June 18, 2010
By Eric Chan, Texas A&M University Ph.D. graduate student:
I woke up around 8:30 a.m. and my advisor (Dr. Kessler) finds my groggy self in the galley to tell me that they're burning oil right next to our ship. We walk out back and there's a billowing black smoke rising from the sea. We looked at the burning smoke with dismay; all that oil burning was sending more carbon dioxide and pollution into the air. Eventually the sun is blotted out by the smoke from the burning oil, a sad sight indeed. It's great we have this opportunity to study this disaster where normally no one would let us dump an immense amount of methane into the water to simulate and study a geologic phenomenon, but as an inhabitant of this planet, seeing the water covered in oily goop and sheen truly is a disheartening scene.
Today we took a look at some our spectroscopy data. The CRDS units we have measure the concentration of carbon dioxide (CO2) and methane (CH4). This is particularly useful since we're determining whether the methane is creeping up to the surface from the leaking oil well. This, coupled with water column profiling, will help us understand how the rapid release of methane is moving through the water column. We've found three distinct drawdowns in dissolved oxygen around 900 meters, 1,050 meters, and 1,200 meters at some stations. We were excited and sampled these three peaks for carbon isotopes of methane. We've collected two dozen or so traps that extract dissolved methane from the collected seawater so we can analyze it and determine the origin of the methane as well as other features.
Daily life on a ship mostly just revolves around working and when not working we try to eat and sleep. The steward Mike is a good cook from [North Carolina] and keeps us well-nourished so we can keep running. Most of us find that the best thing is the freezer full of ice cream that keeps us nice and cheery. I was up for 30 hours on day two, and the pain was medicated with lots of coffee and Monster [energy drink]. The rest of the science crew is in good spirits and motivated to get more data. Everyone tries to help everyone else when we can, especially working these long days.
We take little breaks to take pictures of the oil burning and the oil slicks that cover the sea surface. The odor smells like motor oil mixed with fuel. The last few days have been scattered with thunderstorms and have cleared the air enough so we don't have to wear our respirators as frequently. Overall it's a good cruise experience and I look forward to more chances to study out on the water in the future, hopefully without the massive environmental disaster though.
It's Friday night and we have only 24 hours left to get as many samples as we can.
Image of RV Cape Hatteras scientific workspace by Eric Chan, Texas A&M University Ph.D. graduate student