Oil in the Rain?

RedIbis

Philosopher
RedIbis
Joined
Jul 22, 2007
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I understand that oil doesn't evaporate. But as some have already suggested, if BP is using dispersants, will this allow some oil to be evaporated?

http://www.youtube.com/watch?v=un8co1d4zb4&feature=player_embedded#!

I live on the Gulf Coast, and I am appealing to jref superdebunkers to console me that a result of the spill could not be any oil in the rain.

I also know what the streets look like after a rain, which usually has an oily sheen to it, but it appears to be much more oil than what would be expected.

Please no vitriol, just a civil discussion. I don't have any opinion about this.

ETA: I didn't know where to put this thread since it is science based, but it's about the Gulf Spill.
 
Oil, or at least some of its lighter constituents can evaporate but doesn’t rise the way water vapor does so rain seems unlikley. Even if all the oil evaporated it would still only add up to a small fraction of the unburned petroleum spewing out of the tailpipes of vehicles in the US.
 
Perhaps oily water is getting into the sewer system and backing up after a hard rain, or this is oily runoff from some other source dislodged during the storm.

I suppose we'll know more if this keeps happening. Unless the video is a fake, any of these possibilities is potentially devastating.
 
RedIbis said:
National Weather Service Science and Operations Officer Charlie Paxton says while it's always possible a water spout could pick up some oil and carry it a short distance, the notion of black rain is just not possible. Paxton says that's because oil does not evaporate.
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Sounds oversimplified to me, but not exactly wrong. Oil is a mixture of all sorts of different hydrocarbons with different volatilities. The more volatile fractions will evaporate, and can then (I suppose, I'm no meteorologist) condense and fall with raindrops. However, the black tarry stuff you'll find on beaches is what's left over after the lighter fractions are gone. The lighter fractions are mainly clear liquids - in fact, petrol and diesel before the additives are put in - so they won't turn rain black. The black stuff also won't turn rain black, because it's the part that doesn't evaporate. At least the stuff falling from the sky on you is a bit cleaner; it's not much consolation, I know.

The dispersants won't make more oil evaporate. By allowing the oil to disperse in the water, they'll actually make it evaporate more slowly. I imagine the aim is that, once it's dispersed in the water, it's more accessible to bacteria that can then break it down.

Dave
 
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RedIbis said:
Perhaps oily water is getting into the sewer system and backing up after a hard rain, or this is oily runoff from some other source dislodged during the storm.

I suppose we'll know more if this keeps happening. Unless the video is a fake, any of these possibilities is potentially devastating.
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in low-income neighborhoods around here, its because most of the cars there leak oil and other fluids which mix with the rain and looks just like that video
 
Water spouts are the most serious threat. They can cause it to rain sardines twenty miles inland. For once, you actually do have something real to occupy yourself with.
 
RedIbis said:
That doesn't make me feel better.
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Well, if gasoline did not evaporate it would be very hard to burn. We dump a lot of this stuff in teh atnosphere already, so I am not sure the stuff that goes from teh Gulf spill into the clouds is going to make a huge difference.
 
Dave Rogers said:
Sounds oversimplified to me, but not exactly wrong. Oil is a mixture of all sorts of different hydrocarbons with different volatilities. The more volatile fractions will evaporate, and can then (I suppose, I'm no meteorologist) condense and fall with raindrops. However, the black tarry stuff you'll find on beaches is what's left over after the lighter fractions are gone. The lighter fractions are mainly clear liquids - in fact, petrol and diesel before the additives are put in - so they won't turn rain black. The black stuff also won't turn rain black, because it's the part that doesn't evaporate. At least the stuff falling from the sky on you is a bit cleaner; it's not much consolation, I know.

The dispersants won't make more oil evaporate. By allowing the oil to disperse in the water, they'll actually make it evaporate more slowly. I imagine the aim is that, once it's dispersed in the water, it's more accessible to bacteria that can then break it down.

Dave
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Where do you get your info from? I'm working through a lot of the articles that discuss this now. Whereas the oil might not be readily evaporated, apparently, this nasty Corexit stuff will evaporate and be absorbed by clouds and rain back down to earth.

If we've learned anything, it's that this spill will have repercussions way beyond what it will do to the Gulf.
 
rjh01 said:
Where does the oil that does evaporate go?
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Not into the clouds because AFAIK any hydrocarbon that isn’t already a gas will be heavier then air when it evaporates. Like the unburnt gas from our cars this vapor will break down in sunlight.
 
lomiller said:
Not into the clouds because AFAIK any hydrocarbon that isn’t already a gas will be heavier then air when it evaporates.
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the water droplets that make up a cloud are also heavier than air

but you are correct that evaporated oil will not make it into the upper atmosphere, the reason is just not as simple as "its heavier than air"
 
defaultdotxbe said:
in low-income neighborhoods around here, its because most of the cars there leak oil and other fluids which mix with the rain and looks just like that video
Click to expand...

You can find these micro-slicks during rain showers on almost any street that sees significant automotive traffic. It's not coming from the sky; like defaultdotxbe says, the oil is already on the road.
 
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