What makes a plume?

There is much being made of a dangerous underwater plume in the Gulf of Mexico. Apparently Obama's experts have found 0.5 ppm of oil below the surface of the water. How does this compare to other plumes? Let's consider the fecal matter in the Potomac River. EPA consistently measures 10-20 ppm of fecal matter in the Potomac River. During heavy rain there is up to 3000 ppm.

So there is 20 to 6000 ppm times as much poop in the Potomac as there is oil from the BP oil spill in the Gulf of Mexico. Which body of water do you want to swim in.

Of course the Potomac is close to the White House so the source of the pollution is non stop and no one has the technology to shut it off. At least the oil spill will be stopped this summer and the water will be cleaned up.