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Re: Biology Question on Trees and Polution

In article <3kdp7e$dma@news.panix.com>, Jim Cook <jimcook@panix.com> wrote:
>In article <eeeD5Dx4u.DMv@netcom.com>, 
>eee@netcom.com (Mark Thorson) says:
>>
>>I've crossposted this to sci.environment, where it should have gone in
>>the first place.  Someone there might have the information you seek,
>>however I think you'll be a bit surprised.  At least when you're talking
>>about the hydrocarbons that contribute to haze and smog, trees CAUSE
>>pollution, they don't cure it.
>
>Simonich and Hites (1994) estimated that most of the atmosphere to soil
>flux of polycyclic aromatic hydrocarbons (PAHs) occurs via absorption 
>to plants.  They suggested that this may also be the case for other low
>vapor pressure and hydrophobic atmospheric pollutants -- such as 
>polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls.

Polycyclic aromatics and the other compounds you mention are supposedly evil
chemical wastes, but are produced in small quantity.  Unless you happen to
live in Seveso, Italy, the real meaning of the word pollution mostly translates
into smog.  Trees, lawns, etc. produce volatile organic compounds (VOC's)
which become smog.

>It's true that trees and other plants release hydrocarbons to the 
>atmosphere, and that these hydrocarbons contribute to the formation 
>of smog and haze.  However, the rate limiting reactant in this 
>photochemical reaction is NOx, which is largely anthropogenic in most
>urban areas.

Around here, bread-baking plants have been required, at great expense, to
install scrubbers to remove ethanol from the proofing rooms for bread
dough (ethanol is produced by the yeast which make bread rise).  These
hydrocarbons are taken very seriously by the air pollution people.

>...Simonich, S.L. and Hites, R.A. (1994) Importance of Vegetation
>in Removing Polycyclic Aromatic Hydrocarbons from the Atmosphere.
>Nature, 370, 49-51.
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