| Summary: | 碩士 === 國立中央大學 === 應用地質研究所 === 86 === This paper discusses the influence of water table fluctuation on
redistribution and movement of gasoline in the subsurface and in
the monitoring well, and the development of analytical relations
for the gasoline volume contained in soil with or without free
product. Relevant dynamic problems were studied with sand-box
simulations, while equilibrium problems by mathematical
analysis. Fluids inside the monitoring well move faster than do
they in the surrounding soil as the water table fluctuates.
Therefore, gasoline thickness in the monitoring well decreases
as gasoline flows into the surrounding soil when the water table
rises due to regional groundwater flow, and vice versa. If the
rising of the water table is caused by infiltration from rain
fall or surface recharge, gasoline thickness inside the
monitoring well does not increase significantly. When regional
groundwater flow causes the water table to rise, residual
saturation of gasoline is formed below the rising water table.
As the water table falls, this residual saturation of gasoline
is remobilized to accumulate on top of the falling water table.
Analytical relations for the estimation of gasoline volume
contained in soil with and without free product are obtained,
and they all show gasoline volume in soil is related to soil
characteristics, and invasion depth that is influenced by the
leakage amount and the distance between the water table and the
leakage source. Thus, effective application of remedial measures
needs to know the water table fluctuates. Detailed field
investigation of gasoline contamination requires monitoring
wells as well as soil sampling data.
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