health and safety plan solid waste management unit assessment

STODDAEUI SOLVENT 67-11
67.2.2 Transport and Transformation Processes
'Transport and transformation of Stoddard solvent constituents will
depend on the physicochemical (and biological) properties of the
constituents. Some constituents will dissolve more quickly in the
percolating ground waters and be sorbed less strongly on the soils,
thus being transported more rapidly, and may or may not be susceptible
to degradation by chemical or biological action. Thus, as was shown in
Figure 65-1, the relative concentrations of the constituents of the
solvent WI11 vary with time and distance from the site of
contamination. This effect is called "weathering.' (This term is also
used to describe the changes to petroleum materials following spills
into surface waters where film spreading and breakup, and differential
volatilization, dissolution and degradation are all involved.)
There are no available data specific to the transport and
transformation of Stoddard solvent in soil/ground-water systems. In
general, the low water solubility and moderate vapor pressure of
Stoddard solvent suggest that volatilization With subsequent
photooxidation in the atmosphere may be important. Even though the
most volatile hydrocarbons (i.e., < C,) are not expected to be major'
components of Stoddard solvent, volatilization from surface soils is
expected to be a major fate process for thir alkanes which have very low
water solubility. Tha aromatic hydrocarbons likely to be present in
Stoddard solvent are moderately soluble In water and may be available
to be dissolved in and transported with infiltrating water. Sorption
to organic materials may limit the actual rates of leaching and
volatilization from soils.
As discussed in &tail in Chapter 64, large surface spills or
subsurface discharges of petroleum distillates may result in a separate
organic phase on the surface of the ground water. Migration of the
organic phase may be very different from that of the ground water
itself and the solvent hydrocarbons dissolved in the ground water.
Biodegradation may be an inportant transformation process for -
Stoddard solvent in soil/ground-water systems; some photooxidation of
surface spills may also occur. Data prerentod in Chapter 64 suggest
that microorganisms capable of degrading C, to C,, allphatic and
aromatic hydrocarbons are not uncomn in the environmmnt, and under
conditions favorahlo to microbial activity, biodegradation may be
rapid. It should be mentioned that Walker pi &. (2257) state that
even under optimum conditions, total and complete biodegradation of
petfoleum hydrocarbons is not expected to occur except possibly over an
extremely long time period.
Overall, ground water underlying soil contaminated with Stoddard
solvent hydrocarbons may be vulnerable to contamination by at lout
some of these components. The type of spill (surface VI. sub-surface)
is of importance since volatilization from the surface may be a
significant removal process particularly for the lower molecular weight
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