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On September 19th, nearly five months after the spill started, BP finally sealed the Macondo well. An adjoining relief well had already been completed, and Macondo got a final wallop of cement. This is the coup de grace. A temporary containment cap was placed over the wellhead in July, and a cement filling was installed in August. Now more efforts will turn to assessing and compensating for the damage, which involves several things happening at once. The Natural Resource Damage Assessment process, overseen by the National Oceanic and Atmospheric Administration(NOAA), quantifies the damage and what it might cost to fix it. It figures out BP's bill, in other words. Alongside this, an army of federal and state agencies, government researchers, academic scientists and independent advocates works on pieces of the picture: whether sampled fish show traces of oil in their gall bladders, whether whales are avoiding their usual mating grounds, whether water samples contain more hydrocarbons than would occur from natural seepage. BP has also pledged to spend $50m a year for the next ten years on its own independent research effort, as well as supplying scientists for what the NOAA is doing. Estimating the size of the spill was essential first step. On August 2nd the National Incident Command estimated that the spill amounted to a total of 4.9m barrels of oil. NOAA added an account of where it all went: a quarter dissolved or evaporated by natural means; 17% was siphoned up from the wellhead; 8% was burned off; 16% was dispersed naturally; 8% was dispersed through the prodigious application of chemicals. The remaining 26%, according to NOAA is spread around: some shimmering on the surface as sheen, some buried in layers of sediment on the sea floor. Non-government scientists worry that the spillage estimate is too small. And the dispersed oil has not exactly gone: it simply has a better chance of biodegrading, and less chance of coming ashore. This process is already well under way: the gulf is full of bacteria that happily chomp oil, if they get it in tiny specks. Earlier this month the Joint Analysis Group, another government outfit, reported that the levels of oxygen in the sea were about 20% below normal, though not low enough to endanger marine life. That suggests that the bacteria are indeed at work. Presented with a sudden food source, they are gobbling away, using lots of oxygen to digest it. James Cowan, a Louisiana State oceanographer, is more critical of the use of chemical dispersants. The lighter bits of the dispersed oil may be eaten by bacteria, or will rise the sea surface, to weather or evaporate. But he reckons that the heavy parts have simply sunk to the bottom. From there, they could still work their way into the food chain. It is quite likely, though, that the damage will be a lot less than was feared as the oil was gushing. No hurricanes came to push the slick inland, and most the oil has been successfully kept offshore. So far there has been no discernible effect on fish stocks and almost all the fisheries have now reopened. But it is still early days. Any trouble that may lurk deep in the sea will remain obscure for some time yet.
单选题16.The work of the National Resource Damage Assessment will help______.