http://news.discovery.com/earth/to-measure-the-oil-measure-the-methane.htmlQuestions about how much oil has been spilled in the last month by the Deepwater Horizon oil rig explosion could be answered if scientists move quickly to measure the plumes of dissolved methane gas drifting around the Gulf of Mexico, a geochemist proposed Sunday. Writing in an online publication of the journal Nature, David Valentine of the University of California, Santa Barbara, called for "a concerted community effort" by scientists, federal officials and British Petroleum to devote at least two research vessels to the methane measuring mission during the month of June.
The actual amount of oil spilled -- and still spilling -- into the Gulf is one of the central issues surrounding what Valentine describes as likely "the worst oil spill in US history." While federal and British Petroleum officials continue to estimate the rate of leakage at 5,000 barrels a day, some scientists studying video of the leak concluded last week that the volume could be vastly larger.
"Visual observations of leakage from the ruptured pipe are unreliable because of the turbulent flow and the uncertain water content of the oil-water-gas mixture," Valentine wrote. "Spot measurements of the flux at any given moment can't be scaled up reliably, because the flow may not be constant." And while satellite photos and boat measurements are helpful to assess the extent of the surface slick, he said, "these measures are also highly viable with time, place, weather continues and dispersant application."
Spewing from the ocean floors a mile deep is a mixture that, according to BP, is roughly half methane and other gases by mass and half petroleum compounds, Valentine told Discovery News, and while the oil itself migrates unevenly around the Gulf in ways that are difficult to track, the behavior of methane is more congenial to measurement. "Although methane from surface-vessel spills or shallow-water blowouts escapes into the air, I expect that the vast majority of methane making the long trip to the sea surface from a deep water spill would dissolve," Valentine wrote. "Unlike oil, methane dissolves uniformly in seawater. And the tools are available to measure it accurately and sensitively."...