Good news plus lingering concerns for Deepwater Horizon cleanup workers

Several new studies of air and water near the site of the Deepwater Horizon oil spill conclude that cleanup workers may have escaped harm from one of the most worrisome groups of potentially toxic substances in the oil, according to an article in Chemical & Engineering News (CEN), ACS's weekly news magazine. But it cites concerns that another group of potentially harmful chemicals did escape from the water and could create a health hazard for cleanup workers.

The article, by C&EN Senior Editor Elizabeth Wilson, describes research showing that benzene, toluene, ethylbenzene, and xylene — collectively termed BTEX — remained dissolved in the Gulf of Mexico, and did not vaporize into the air where they could be inhaled by cleanup workers. The spill began on July 20, 2010 with an explosion on the Deepwater Horizon facility, 50 miles off the coast of Louisiana, killing 11 oil workers. By the time the well was capped 87 days later, 4.9 million barrels (206 million gallons) of oil had spilled.

Tempering that apparent good news for the health of cleanup workers, however, are concerns that other substance released by the crude oil, substances that do not dissolve as well in water, die become airborne during the 2010 disaster. If so, they could pose a health threat to cleanup workers, the article notes.

More information: "Hyrdocarbons at Gulf Spill Surface" is available at http://pubs.acs.or … 937sci3.html

Provided by American Chemical Society (news : web)

Deep below the Deepwater Horizon oil spill: New molecular model better explains diffusion of spill under water

 For the first time, scientists gathered oil and gas directly as it escaped from a deep ocean wellhead -- that of the damaged Deepwater Horizon oil rig. What they found allows a better understanding of how pollution is partitioned and transported in the depths of the Gulf of Mexico and permits superior estimation of the environmental impact of escaping oil, allowing for a more precise evaluation of previously estimated repercussions on seafloor life in the future.

The explosion of the Deepwater Horizon rig in April 2010 was both a human and an environmental catastrophe. Getting the spill under control was an enormous challenge. The main problem was the depth of the well, nearly 1,500 meters below the sea surface. It was a configuration that had never been tried before, and the pollution it unleashed after methane gas shot to the surface and ignited in a fiery explosion is also unequalled. Much research has been done since the spill on the effects on marine life at the ocean's surface and in coastal regions. Now, École Polytechnique Fédérale de Lausanne (EPFL) professor Samuel Arey and the Woods Hole Oceanographic Institute reveal in the advance online edition of Proceedings of the National Academy of Sciences how escaped crude oil and gas behave in the deep water environment.

Into the deep

In June 2010, with the help of a remotely operated vehicle (ROV), Woods Hole scientists reached the base of the rig and gathered samples directly from the wellhead using a robotic arm. The oceanographers also made more than 200 other measurements at various water depths over a 30-kilometer area. These samples were then analyzed with the help of the US National Oceanic and Atmospheric Administration and the dissolution of hydrocarbons was modeled at EPFL. This model showed how the properties of hydrocarbons are important in understanding the wellhead structure and pollution diffusion -- how pollution spreads out -- in the depths.

From the ROV to the lab

Lab analysis led the scientists to describe for the first time the physical basis for the deep sea trajectories of light-weight, water-soluble hydrocarbons such as methane, benzene, and naphthalene released from the base of the rig. The researchers observed, for example, that at a little more than 1,000 meters below the surface, a large plume spread out from the original gusher, moving horizontally in a southwest direction with prevailing currents. Unlike a surface spill, from which these volatile compounds evaporate into the atmosphere, in the deep water under pressure, light hydrocarbon components predominantly dissolve or form hydrates, compounds containing water molecules. And depending on its properties, the resulting complex mixture can rise, sink, or even remain suspended in the water, and possibly go on to cause damage to seafloor life far from the original spill.

By comparing the oil and gas escaping from the well with the mixture at the surface, EPFL's Samuel Arey, head of Environmental Chemistry Modeling Laboratory, and colleagues were able to show that the composition of the deep sea plumes could be explained by significant dissolution of light hydrocarbons at 1 kilometer depth. In other words, an important part of the oil spreads out in underwater plumes, so we need a more precise evaluation of previously estimated repercussions on seafloor life in the future. Arey's methodology offers a better estimation of how pollution travels and the potential deep sea consequences of spills.

"Modeling the environmental fate of hydrocarbons in deep water ecosystems required a new approach, with a global view, in order to correctly understand the impact of the pollution," explains Arey. This research will have a significant impact on assessments of the environmental impact of deep water oil spills.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Ecole Polytechnique Fédérale de Lausanne, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher M. Reddy, J. Samuel Arey, Jeffrey S. Seewald, Sean P. Sylva, Karin L. Lemkau, Robert K. Nelson, Catherine A. Carmichael, Cameron P. McIntyre, Judith Fenwick, G. Todd Ventura, Benjamin A. S. Van Mooy, Richard Camilli. Science Applications in the Deepwater Horizon Oil Spill Special Feature: Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1101242108

First study of dispersants in Gulf spill suggests a prolonged deepwater fate

To combat last year's Deepwater Horizon oil spill, nearly 800,000 gallons of chemical dispersant were injected directly into the oil and gas flow coming out of the wellhead nearly one mile deep in the Gulf of Mexico. Now, as scientists begin to assess how well the strategy worked at breaking up oil droplets, Woods Hole Oceanographic Institution (WHOI) chemist Elizabeth B. Kujawinski and her colleagues report that a major component of the dispersant itself was contained within an oil-gas-laden plume in the deep ocean and had still not degraded some three months after it was applied.

While the results suggest the dispersant did mingle with the oil and gas flowing from the mile-deep wellhead, they also raise questions about what impact the deep-water residue of oil and dispersant -- which some say has its own toxic effects -- might have had on environment and marine life in the Gulf.

"This study gives our colleagues the first environmental data on the fate of dispersants in the spill," said Kujawinski, who led a team that also included scientists from UC Santa Barbara. "These data will form the basis of toxicity studies and modeling studies that can assess the efficacy and impact of the dispersants.

"We don't know if the dispersant broke up the oil," she added. "We found that it didn't go away, and that was somewhat surprising."

The study, which appears online Jan. 26 in the American Chemical Society (ACS) journal Environmental Science &Technology, is the first peer-reviewed research to be published on the dispersant applied to the Gulf spill and the first data in general on deep application of a dispersant, according to ACS and Kujawinski. Some previous studies had indicated that dispersants applied to surface oil spills can help prevent surface slicks from endangering marshes and coastlines.

Kujawinski and her colleagues found one of the dispersant's key components, called DOSS (dioctyl sodium sulfosuccinate), was present in May and June -- in parts-per-million concentrations--in the plume from the spill more than 3,000 feet deep. The plume carried its mixture of oil, natural gas and dispersant in a southwest direction, and DOSS was detected there at lower (parts-per-billion) concentrations in September.

Using a new, highly sensitive chromatographic technique that she and WHOI colleague Melissa C. Kido Soule developed, Kujawinski reports those concentrations of DOSS indicate that little or no biodegradation of the dispersant substance had occurred. The deep-water levels suggested any decrease in the compound could be attributed to normal, predictable dilution. They found further evidence that the substance did not mix with the 1.4 million gallons of dispersant applied at the ocean surface and appeared to have become trapped in deepwater plumes of oil and natural gas reported previously by other WHOI scientists and members of this research team. The team also found a striking relationship between DOSS levels and levels of methane, which further supports their assertion that DOSS became trapped in the subsurface.

Though the study was not aimed at assessing the possible toxicity of the lingering mixture -- Kujawinski said she would "be hard pressed to say it was toxic" -- it nevertheless warrants toxicity studies into possible effects on corals and deep-water fish such as tuna, she said. The EPA and others have already begun or are planning such research, she added.

David Valentine of UC Santa Barbara and a co-investigator in the study, said, "This work provides a first glimpse at the fate and reactivity of chemical dispersants applied in the deep ocean. By knowing how the dispersant was distributed in the deep ocean, we can begin to assess the subsurface biological exposure, and ultimately what effects the dispersant might have had."

"The results indicate that an important component of the chemical dispersant injected into the oil in the deep ocean remained there, and resisted rapid biodegradation," said Valentine, whose team collected the samples for Kujawinski's laboratory analysis. "This knowledge will ultimately help us to understand the efficacy of the dispersant application, as well as the biological effects."

Kujawinski and Valentine were joined in the study by Soule and Krista Longnecker of WHOI, Angela K. Boysen a summer student at WHOI, and Molly C. Redmond of UC Santa Barbara. The work was funded by WHOI and the National Science Foundation. The instrumentation was funded by the National Science Foundation and the Gordon and Betty Moore Foundation.

In Kujawinski's technique, the target molecule was extracted from Gulf water samples with a cartridge that isolates the DOSS molecule. She and her colleagues then observed the molecule through a mass spectrometer, ultimately calculating its concentration levels in the oil and gas plume. This method is 1,000 times more sensitive than that used by the EPA and could be used to monitor this molecule for longer time periods over longer distances from the wellhead, she said.

"With this method, we were able to tell how much [dispersant] was there and where it went," Kujawinski said. She and her colleagues detected DOSS up to around 200 miles from the wellhead two to three months after the deep-water injection took place, indicating the mixture was not biodegrading rapidly.

"Over 290,000 kg, or 640,000 pounds, of DOSS was injected into the deep ocean from April to July," she said. "That's a staggering amount, especially when you consider that this compound comprises only 10% of the total dispersant that was added."

Kujawinski cautioned that "we can't be alarmist" about the possible implications of the lingering dispersant. Concentrations considered "toxic" are at least 1,000 times greater than those observed by Kujawinski and her colleagues, she said. But because relatively little is known about the potential effects of this type of dispersant/hydrocarbon combination in the deep ocean, she added, "We need toxicity studies."

"The decision to use chemical dispersants at the sea floor was a classic choice between bad and worse," Valentine said. "And while we have provided needed insight into the fate and transport of the dispersant we still don't know just how serious the threat is; the deep ocean is a sensitive ecosystem unaccustomed to chemical irruptions like this, and there is a lot we don't understand about this cold, dark world."

"The good news is that the dispersant stayed in the deep ocean after it was first applied," Kujawinski says. "The bad news is that it stayed in the deep ocean and did not degrade."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Woods Hole Oceanographic Institution.

Journal Reference:

Elizabeth B. Kujawinski, Melissa C. Kido Soule, David L. Valentine, Angela K. Boysen, Krista Longnecker, Molly C. Redmond. Fate of Dispersants Associated with the Deepwater Horizon Oil Spill. Environmental Science & Technology, 2011; : 110126010225058 DOI: 10.1021/es103838p

First study of dispersants in Gulf spill suggests a prolonged deepwater fate

ScienceDaily (Jan. 26, 2011) — To combat last year's Deepwater Horizon oil spill, nearly 800,000 gallons of chemical dispersant were injected directly into the oil and gas flow coming out of the wellhead nearly one mile deep in the Gulf of Mexico. Now, as scientists begin to assess how well the strategy worked at breaking up oil droplets, Woods Hole Oceanographic Institution (WHOI) chemist Elizabeth B. Kujawinski and her colleagues report that a major component of the dispersant itself was contained within an oil-gas-laden plume in the deep ocean and had still not degraded some three months after it was applied.

While the results suggest the dispersant did mingle with the oil and gas flowing from the mile-deep wellhead, they also raise questions about what impact the deep-water residue of oil and dispersant -- which some say has its own toxic effects -- might have had on environment and marine life in the Gulf.

"This study gives our colleagues the first environmental data on the fate of dispersants in the spill," said Kujawinski, who led a team that also included scientists from UC Santa Barbara. "These data will form the basis of toxicity studies and modeling studies that can assess the efficacy and impact of the dispersants.

"We don't know if the dispersant broke up the oil," she added. "We found that it didn't go away, and that was somewhat surprising."

The study, which appears online Jan. 26 in the American Chemical Society (ACS) journal Environmental Science &Technology, is the first peer-reviewed research to be published on the dispersant applied to the Gulf spill and the first data in general on deep application of a dispersant, according to ACS and Kujawinski. Some previous studies had indicated that dispersants applied to surface oil spills can help prevent surface slicks from endangering marshes and coastlines.

Kujawinski and her colleagues found one of the dispersant's key components, called DOSS (dioctyl sodium sulfosuccinate), was present in May and June -- in parts-per-million concentrations--in the plume from the spill more than 3,000 feet deep. The plume carried its mixture of oil, natural gas and dispersant in a southwest direction, and DOSS was detected there at lower (parts-per-billion) concentrations in September.

Using a new, highly sensitive chromatographic technique that she and WHOI colleague Melissa C. Kido Soule developed, Kujawinski reports those concentrations of DOSS indicate that little or no biodegradation of the dispersant substance had occurred. The deep-water levels suggested any decrease in the compound could be attributed to normal, predictable dilution. They found further evidence that the substance did not mix with the 1.4 million gallons of dispersant applied at the ocean surface and appeared to have become trapped in deepwater plumes of oil and natural gas reported previously by other WHOI scientists and members of this research team. The team also found a striking relationship between DOSS levels and levels of methane, which further supports their assertion that DOSS became trapped in the subsurface.

Though the study was not aimed at assessing the possible toxicity of the lingering mixture -- Kujawinski said she would "be hard pressed to say it was toxic" -- it nevertheless warrants toxicity studies into possible effects on corals and deep-water fish such as tuna, she said. The EPA and others have already begun or are planning such research, she added.

David Valentine of UC Santa Barbara and a co-investigator in the study, said, "This work provides a first glimpse at the fate and reactivity of chemical dispersants applied in the deep ocean. By knowing how the dispersant was distributed in the deep ocean, we can begin to assess the subsurface biological exposure, and ultimately what effects the dispersant might have had."

"The results indicate that an important component of the chemical dispersant injected into the oil in the deep ocean remained there, and resisted rapid biodegradation," said Valentine, whose team collected the samples for Kujawinski's laboratory analysis. "This knowledge will ultimately help us to understand the efficacy of the dispersant application, as well as the biological effects."

Kujawinski and Valentine were joined in the study by Soule and Krista Longnecker of WHOI, Angela K. Boysen a summer student at WHOI, and Molly C. Redmond of UC Santa Barbara. The work was funded by WHOI and the National Science Foundation. The instrumentation was funded by the National Science Foundation and the Gordon and Betty Moore Foundation.

In Kujawinski's technique, the target molecule was extracted from Gulf water samples with a cartridge that isolates the DOSS molecule. She and her colleagues then observed the molecule through a mass spectrometer, ultimately calculating its concentration levels in the oil and gas plume. This method is 1,000 times more sensitive than that used by the EPA and could be used to monitor this molecule for longer time periods over longer distances from the wellhead, she said.

"With this method, we were able to tell how much [dispersant] was there and where it went," Kujawinski said. She and her colleagues detected DOSS up to around 200 miles from the wellhead two to three months after the deep-water injection took place, indicating the mixture was not biodegrading rapidly.

"Over 290,000 kg, or 640,000 pounds, of DOSS was injected into the deep ocean from April to July," she said. "That's a staggering amount, especially when you consider that this compound comprises only 10% of the total dispersant that was added."

Kujawinski cautioned that "we can't be alarmist" about the possible implications of the lingering dispersant. Concentrations considered "toxic" are at least 1,000 times greater than those observed by Kujawinski and her colleagues, she said. But because relatively little is known about the potential effects of this type of dispersant/hydrocarbon combination in the deep ocean, she added, "We need toxicity studies."

"The decision to use chemical dispersants at the sea floor was a classic choice between bad and worse," Valentine said. "And while we have provided needed insight into the fate and transport of the dispersant we still don't know just how serious the threat is; the deep ocean is a sensitive ecosystem unaccustomed to chemical irruptions like this, and there is a lot we don't understand about this cold, dark world."

"The good news is that the dispersant stayed in the deep ocean after it was first applied," Kujawinski says. "The bad news is that it stayed in the deep ocean and did not degrade."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Woods Hole Oceanographic Institution.

Journal Reference:

Elizabeth B. Kujawinski, Melissa C. Kido Soule, David L. Valentine, Angela K. Boysen, Krista Longnecker, Molly C. Redmond. Fate of Dispersants Associated with the Deepwater Horizon Oil Spill. Environmental Science & Technology, 2011; : 110126010225058 DOI: 10.1021/es103838p

Note: If no author is given, the source is cited instead.

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