Environmental Implications of a Massive Oil Spill and

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surface. Near the origin, large particles would create a regime of extended
partial shade. All wavelengths of light would be affected, including those
that drive photosynthesis. However, large particles tend to deposit
relatively quickly as the plume wanders across the landscape. If the plume
always followed the same path, then we would expect there to be a swath of
reduced crop productivity beneath the plume. But in practice the plume
would meander with the wind and so the effect would be distributed and
diluted across a broad region rather than focussed on some specific locale.

The average size of particles in the plume would decrease with increasing
distance from the origin. Not only do the larger particles drop out first,
but new small particles would be generated by chemical reactions
occurring in the plume. After the large particles had mostly dropped out,
the remaining small particles would act more as scatterers of light than as
blockers. Even though the direct solar beam may be somewhat reduced,
experiments have shown that most of the reduction is made up by increased
scattered light arriving at the surface. Thus, the total radiation available
for photosynthesis would not remain as low as would be expected if the
direct solar beam only were considered. The overall consequence is that
effects on solar radiation and hence on crop productivity would be largest
near the fire, and would diminish rapidly with distance from it. If crops
are significantly affected, subsistence farming, herding, and grazing could
also be impacted.


6.  Would there be effects from other constituents in the~smoke?
The oil contains about 2.5% sulfur, which will produce significant
concentrations of sulfur dioxide if burned in large quantities. In additiOn,
there would be concentrations of nitrogen oxides that, together with the
sulfur dioxide, would cause any rain gene~ted from the same air mass as
the plume to be acidified more than normal. There could then be localized
deposition comparable to, or perhaps somewhat in excess of that observed
downwind of industrialized areas (e.g. in Europe or eastern North
America). Another potential effect from the release of nitrogen oxides and
unburned hydrocarbons could be the formation of tropospheric smog.
This effect would be greatest in summer when ultraviolet light and
temperatures are highest.


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