Web Concepts

Posts Tagged ‘dispersants’

Advanced ocean science tech helps researchers study the spill

The night of June 21, 2010, Reddy and colleagues from the Woods Hole Oceanographic Institution were whisked off their research vessel Endeavor to collect samples directly from the blown Macondo well, which had been spewing oil and natural gas into the Gulf of Mexico for two months. They had 12 hours to do something that had never been done before: Use a robot arm to stick a special bottle directly into the hot hydrocarbons. Now, a year later, their analysis explains just what came out of the well, and sheds more light on what happened to it.

It turns out that certain chemicals in the well behave differently under high pressure than they do at the surface. This explains why some chemicals, but not others, made their way into the huge 22-mile plume of oil that Reddy et. al uncovered last summer. It also explains why some scientific papers examining the spill have seemed to contradict each other, according to Don Rice, director of the National Science Foundation’s chemical oceanography program.

“We now have a far better understanding of how and why an oil ‘spill’ into the ocean from below differs from one from above. The significance of this work extends well beyond the Gulf of Mexico,” he said in a statement.

One of the most confounding problems with the oil spill was scientific uncertainty — about how much oil was leaking into the Gulf, and about what exactly it was, both of which would explain where the oil would go. Reddy and colleagues needed to go directly to the source — the gusher at 5,000 feet below the surface — to see the compounds and therefore understand what would happen to the plume. This sample is called an “end member,” Reddy explained in an interview. A significant fraction of the gusher consisted of hot gas, mainly methane, so this proved a difficult task.

“If you tried to lower a traditional tool into that boiling cauldron and then close it and bring it up to the surface, that bottle would explode. A tiny methane bubble at 5,000 feet becomes a giant methane bubble at atmospheric pressure,” Reddy said.

The research team turned to Woods Hole geochemist Jeff Seewald, who developed a tool called an isobaric gas-tight sampler. It’s intended for collecting fluids from deep-sea hydrothermal vents. They used an oil industry ROV to place the IGT sampler directly over the broken riser pipe, and they collected the only undiluted, non-degraded sample from the spill.

The team found a gas-to-oil ratio of 1,600 cubic feet of gas per barrel of oil, according to a paper on the findings published this week in the Proceedings of the National Academy of Sciences and funded by the NSF. Based on this ratio, and using the federal government’s estimate of 4.1 million barrels of oil, Reddy et. al estimate 1.7 × 1011 g of methane, ethane and propane leaked into the Gulf. That’s about 105 tons. That’s a lot of methane.

But perhaps more interesting is the makeup of the plume, which mostly comprised benzene, toluene, ethybenzene, and total xylenes, or BTEX. BTEX compounds only represented about 2 percent of the oil that came out of the well, but almost 100 percent of the deep-sea plume. They apparently took a right-hand turn 3,000 feet below sea level, whereas the other hydrocarbons — like methane — degraded, washed on shore, were eaten by bacteria, or were burned in the fires that Reddy experienced while gathering his sample.

Studying the plume also required a bit of technical wizardry, Reddy said. WHOI researcher Richard Camilli built a super-sensitive mass spectrometer, which can instantly identify minute quantities of petroleum and other chemical compounds. This tool was used in the initial plume studies last summer, and it helped researchers quantify how the plume and the wellhead gusher were different.

“It shows some of these compounds are likely to evaporate quicker, at shallower depths. Oil is made up of many compounds, and they all have different chemical and physical properties. This work highlights that. Those properties determine what chemicals went into the plume,” Reddy said.

On the surface, this is all different — BTEX compounds quickly volatilize and evaporate into the atmosphere.

“In the case of the Deepwater Horizon oil spill, however, gas and oil experienced a significant residence time in the water column with no opportunity for the release of volatile species to the atmosphere,” the researchers write in the PNAS paper. “Hence, water-soluble petroleum compounds dissolved into the water column to a much greater extent than is typically observed for surface spills.”

The good news is that BTEX is not toxic to marine organisms until it reaches much higher levels than the researchers found in the Gulf. But neurological impairments can occur at lower concentrations, according to the National Science Foundation. It remains to be seen how the persistent BTEX may have affected sea life.

Meanwhile, Reddy and his colleages are still collecting samples from the beaches lining the Gulf Coast. He praised the National Science Foundation for funding ongoing oil spill research programs, which proved useful in the Deepwater Horizon crisis.

“We will continue to hunt and look for remnants of this oil for as long as we can be funded,” he said. “There’s a lot to be learned, about what compounds resist degradation from nature. It sheds tremendous light on this field.”

Samantha Joye, a professor in the Department of Marine Sciences at the University of Georgia, set sail August 21 on the research vessel Oceanus and has been posting blog updates throughout the mission. Over the weekend, she wrote that her team found a layer of oil in a valley on the seafloor, about 18 miles from the wellhead. It is two inches thick in some spots, and it rests on top of recently dead sea creatures like shrimp and tubeworms.

Joye expected to find some oil on the seafloor, she told the AP — just not that much. Her team is the second in as many months to announce finding oil at the bottom; last month, a University of South Florida crew reported finding oil droplets 1.4 miles beneath the surface.

The presence of seafloor oil is another blow to the theory that most of the spilled oil disappeared. Scientists previously said plenty of oil was floating in an invisible plume, and while yet another research team said microbes were eating it, not all of it could be accounted for. Several experts, including some government scientists, believe at least some of the oil sank to the bottom, and that’s what Joye’s research seems to prove.

Although she can’t be certain until they conduct further tests this week, the oil almost certainly came from the spill and not a natural seep, Joye said. It clearly came from above the seafloor, not below, she says in her blog post.

The oil layer is pretty dispersed, indicating that chemical dispersants broke it down into small droplets. In an interview with NPR, she also reported finding small tar balls that look like cauliflower heads. While dispersants likely helped some of the oil sink to the bottom, Joye said natural processes also played a role. As microorganisms break down oil, they excrete mucus, which eventually sinks to the bottom.

Government scientists acknowledge they have not done a good enough job looking for oil at the bottom of the sea. It’s partly because the environment is so difficult — teams have to use send 1,000-pound vessels to the seafloor where they can pull up core samples. The AP quoted a NOAA official saying government and BP vessels will plumb the depths in the coming weeks.

[AP]

Two Air Force C-130 Hercules aircraft will help contain what may be the greatest oil spill disaster in history

Two of four modified C-130s have deployed to the Gulf of Mexico from the 757th Airlift Squadron at Youngstown ARS, Ohio. They typically spray pesticides or fire retardant using the Modular Aerial Spray System (MASS), although other Air National Guard units have the Modular Aerial Fire Fighting System (MAFFS). A newer MAFFS 2 version can dispense 30,000 pounds of retardant in just 3 to 5 seconds from one nozzle at almost 14,000 pounds of thrust. Last year, PopSci took a tour of a firefighting 747 that uses similar technology.

Such flying behemoths are just the latest weapon being thrown into the desperate battle to contain the oil slick. The Macondo well has been spilling an estimated 5,000 barrels of oil per day into the Gulf since the Deepwater Horizon rig exploded and sank on April 20. Controlled burning has only had limited impact on the spill, and robot submarines have failed to activate a cutoff valve to cap the undersea well leaking oil into the Gulf of Mexico.

BP has corralled almost 106,000 gallons of dispersant -- one third of the world's supply -- to try and break up the oil slick. But the unfolding disaster has already shut down fishing between the mouth of the Mississippi River in Louisiana and Florida's Pensacola Bay. That area provides the majority of U.S. production of oyster and shrimp, as part of the $1.8 billion seafood industry in the Gulf that's second only to Alaska, Reuters reports.

As if to underline the magnitude of the event, the U.S. Environmental Protection Agency has an open submission form for anyone with a tech solution to the oil cleanup problem. Just make sure to note the cost, because BP already faces perhaps the most expensive oil cleanup ever -- and that's not including the collateral environmental damage which may very well cripple the Gulf fishing and tourism industries.

[via Ares Defense Blog]