health and safety plan solid waste management unit assessment

FUEL OILS
Migration through soils may be retarded by sorption. Sorption is
expected to be significant for high molecular weight aliphatics,
particularly > C,,. Migration is expected to be fastest through
previously contaminated soils where the sorptive sites may be
unavailable; on the other hand, soil-water content increases sorption
and slows migration of hydrocarbons. In fissured rock, the migration
of hydrocarbons is much less uniform than in porous soils. Preferential
spreading through crevices, sometimes changing the direction of
flow, may occur. Determination of the potential ground-water
contamination in fissured rock is thus very difficult (1811).
The water-soluble portion of No. 2 fuel oil (a higher temperature
distilling fraction than diesel oil) was shown to be almost entirely
aromatic (99%) even though the product itself was 48% aliphatic; the
aliphatic fuel oil hydrocarbons have very low water solubility compared
with the aromatics (1849.2238). 'Ihe largest percentage (40%) of the
water-soluble fraction of fuel oil was represented by C,,-aromatics
(1849). In deep, saturated soils with no soil air, the aromatics
represent the greatest threat of contamination to ground-water
supplies. Solubility in aqueous solution of polar, non-hydrocarbon
components of some higher boiling petroleum fractions such as diesel
oil and other fuel oils has also been reported (2238).
In summary, the physical distribution
affects its impact on, and removal from, the
of fuel oil contamination
soil environment. Lateral
spreading along the surface increases the initial contaminated area
while facilitating evaporative removal or sorption of different
hydrocarbons. Subsurface release or vertical penetration mediated by
gravitation and capillary forces decreases evaporation, reduces the
importance of some transformation pathways (see below), and may lead to
ground-water contamination.
Photooxidation has been reported to play a significant role in the
chemical degradation of petroleum hydrocarbons in the sunlit
environment (1845,1848,2252,2259,2337). Alkanes, benzenes, and
mono-substituted benzenes have been shown to be relatively resistant to
photolysis in aqueous systems; xylenas photolyzed slowly while
trisubstituted benzenes and naphthalenes photolyzsd at rates
competitive with volatilization (1845). Lee & a. report that
anthracene and other polycyclic aromatic hydrocarbons (PAH) in the
carbon range of diesel fuel are subject to photochemical oxidation:
benzo(a)pyrene is the most susceptible of the PAH compounds, suggesting
that the residual' fuel oils may be even more affected by
photodegradation than diesel oil. Penetration of oil below the soil
surface limits exposure to solar radiation while extensive lateral
spreading of oil over impermeable or rocky surfaces may promote
substantial photooxidative degradation. The oxygenated products of
photooxidation are generally more water-soluble than the parent
hydrocarbons and are thus more likely to be leached from soil: enhanced
toxicity of the oxygenated hydrocarbons has also been observed (2248,
2252).
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