First, NPR has a story on a group of scientist and engineers who have calculated the daily output of the broken pipe and come up with an estimate that is dramatically higher than the official numbers.
Steven Wereley, an associate professor of mechanical engineering at Purdue University, analyzed videotape of the seafloor gusher using a technique called particle image velocimetry.
A computer program simply tracks particles and calculates how fast they are moving. Wereley put the BP video of the gusher into his computer. He made a few simple calculations and came up with an astonishing value for the rate of the oil spill: 70,000 barrels a day — much higher than the official estimate of 5,000 barrels a day.
The method is accurate to a degree of plus or minus 20 percent.
Wereley's calculations were backed up by scientists and engineers at other institutions. Needless to say, BP disputes these figures. But even at BP's absurdly low estimate - 5,000 barrels a day - this is shaping up to be even worse than the Exxon Valdez spill.
Deborah Blum over at ScienceBlogs has a post on the relative toxicity of the oil in the Gulf and the chemical dispersant being used to break it down. The standard toxicity test for chemical compounds is called the LD50. LD stands for Lethal Dose and 50 indicates 50 percent. So, LD50 means the lowest dose at which a material kills half of the test subjects. Blum did some digging on the LD50s for crude oil and the dispersant being used (Corexit 9500) and came up with some distressing results: turns out that pouring Corexit 9500 on crude oil actually makes the resulting mixture even more toxic.
The results differ by species and by time as well as by amount of poison, The EPA numbers for Corexit 9500 (the formula used most heavily by BP) show that at 2.62 ppm, the dispersant kills half the silver fish in 96 hours/ four days. At a slightly higher concentration - 3.4 ppm - the compound kills half the little shrimp in two days.
As for crude oils, a very decent analysis by the American Petroleum Institute shows that all are toxic, but their effects vary with thickness and with the different chemistry seen in say, oil from the Gulf of Mexico and oil from Kuwait. The best estimate I've seen for South Louisiana Crude - after hours of exasperated research - comes from thesis work done at Louisiana State University several years ago. For instance, the study found that Louisiana crude had an LC50 of 4250 ppm for the warm-water loving killifish.
This suggests that crude oil is less acutely poisonous than chemical dispersants. But here's the really interesting finding in that terrific little study. Adding a dispersant - specifically Corexit 9500 - made the oil more poisonous. A lot more poisonous.
The "dispersed" oil had an LC50 of 317.7 ppm, making it more than 11 times more lethal in its effects. The study found a similar worsening for white shrimp, although not quite as dramatic. "Dispersed oils were more toxic than crude oils," noted the report.
Finally, The Big Picture has a feature on the spill. I highly recommend it. Beautiful pictures of awful stuff.
Bottlenose dolphins swim through oily water
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