Gulf Oil Spill and Toxic Chemicals

no my friend water much heavier than petrol

petrol will be on the top of the water

Of course petroleum is lighter than oil and it should float except when presented with chemicals dispersants such as those being used. (A side note here. It was said that 3 distinct layers of oil have supposedly been found in the Gulf and occur some where are around the depths of 300', 1000' and 1500' or numbers close to these) However, according to the conversation I heard from a petrochemical expert, "the water in the Gulf is acting as a scrubber" for the chemicals described earlier. I know little about the chemical make-up of the crude oil coming out of the Gulf bottom. However, I do know that fracturing and distilling of the crude oil is done in cracking towers with catalysts to create many of the chemicals we now use in our car engines, dish soap, baby oil, Vaseline, paraffin, plastics, fertilizers, etc. I am looking for a semi technical explanation of the scrubbing process referred to and the length of time the hydrocarbons will stay resident in the water. Do they break down? If so, into what form? Do they evaporate when contacting the surface? If so, what is their persistence? Then, do they go high into the atmosphere and pose a problem for the ozone layer like CFCs? I know from MSDS (Material Safety Data Sheets) sheets that the hydrocarbons listed are highly toxic and dangerous. They are known carcinogens. I am interested in their persistence and eventual subcomponents.