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Oily Rain
Name: Benjie
Status: other
Grade: 12+
Location: SC
Country: USA
Date: N/A
Question:
I read here that oil does evaporate:
http://www.newton.dep.anl.gov/askasci/chem03/chem03025.htm
with the churning of waves, rain, and time of year, do the answers suggest
that one can expect oily rain in the Gulf Coast?
Replies:
Crude oil is a mixture of any number of different organic molecules,
some relatively light (such as methane) and some very heavy such as
octane or kerosene. What will evaporate are the lighter
molecules. The heavier molecules are what give oil its slick or
oily feel. The chances of these evaporating quickly enough to
affect the local weather is very small. So, no, you will probably
not feel oily anything unless you are very close to the venting well.
If conditions were just right, you might get rain laced with say
octane, but not rain that would feel oily to the touch. In
addition, because the evaporation is occurring in the open ocean,
winds should disperse the evaporated molecules widely. The chance
of having a high enough concentration in any area such that the
hydrocarbons could be detected by our five senses as very small indeed.
R. W. "Bob" Avakian
Instructor
B.S. Earth Sciences; M.S. Geophysics
Oklahoma State Univ. Inst. of Technology
The first part of the question should be about the evaporation rate of crude
oil.
I found the following paper from the Canadian Environmental Technology
Department which addresses this issue:
http://www.mms.gov/tarprojects/120/120BG.PDF
It says that in a few days, light crude oil can evaporate as much as 75% of
the starting oil mass
And medium crudes up to 40%. Heavy or residual oils may only evaporate 10%
of the starting oil mass.
I have never experienced an oily rain and I could not find any references to
oily rain on the Internet except from a bicycler whose pant leg got soiled
by oil from his chain.
My guess is that the overall volume of the atmosphere overwhelms any
evaporated oil products
And that an oily rain fall is highly unlikely. There may be some petroleum
products in a rain fall, but they would not be detectable by people's normal
senses.
Sincere regards,
Mike Stewart
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Update: June 2012
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