Transport Analysis — Basic Predictive
Approach of the Movement of
Pollutants through Soil
DENNIS B. CEARLOCK, Engineer
Battelle Memorial Institute
Pacific Northwest Laboratory
Richland, Washington
INTRODUCTION
An accurate knowledge of the concentration distribution of pollutants in a
ground water flow system is an essential element in effective management of waste
disposal facilities and water reclamation projects that discharge their effluents to
the ground. This type of information is necessary to efficiently utilize the purification and retention capabilities of a ground water flow system. Also, a direct
monetary benefit might result from the reduction in the amount of pretreatment
required prior to discharge to the ground. Such information is often needed to assure the public and regulatory agencies that the concentration of pollutants in the
groundwater is within acceptable limits and that there are control measures to
maintain the concentration of pollutants below acceptable limits.
The transport equation is the analysis tool with which concentration distributions of pollutants in a ground water flow system can be determined. Basically,
the transport equation describes two independent phenomena, fluid movement
and pollutant reactions (the reactions of the pollutant with its environment). As
a result of the complexity of each phenomenon, the analysis is simplified by investigating them separately. The transport equation then combines these into one
interrelated equation which yields the concentration distribution of the pollutants
involved.
TRANSPORT ANALYSIS
Traditional Approach
The traditional approach of investigating pollutant transport through soils has
been to consider it as a single effect. The emphasis has been put on investigating
rates of reactions with less attention given to the influence of the flow system on
the measured results. Therefore, the data collected from such experiments may
have limited application with respect to diffusion and dispersion considerations in
field problems unless they have the same boundary conditions and flow system,
since any experimentally determined coefficients would contain the influence of
the previously stated conditions and could not be separated into individual effects.
These investigations are usually one-dimensional column experiments; therefore
the results may not be applicable to multidimensional transport problems. This
can severely limit their usefulness, since most field problems are multidimensional. To insure applicability of one-dimensional laboratory investigations to
multidimensional field problems, the two phenomena peculiar to pollutant transport (fluid movement and pollutant reactions) should be investigated separately.
Separation of the two phenomena in the investigational period also reduces the
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