dc.contributor.advisor Tomson, Mason B. Clark, Gary Lee 2009-06-04T00:39:56Z 2009-06-04T00:39:56Z 1990 https://hdl.handle.net/1911/16332 The rate of movement of contaminants in groundwater is a topic of environmental importance and public concern. Early work in contaminant transport showed that the ratio of the velocity of the water to the velocity of the contaminant (v$\sb{\rm w}$/v$\sb{\rm c}$ or retardation, R) in a flowing saturated soil column can be determined using known values of soil density, soil porosity, percent organic carbon in the soil, and the octanol-water partition coefficient of the contaminant. More recent studies indicate that the retardation of the contaminant in a soil may vary due to soil/contaminant isotherm non-linearity and non-equilibrium conditions in the column. In this research, the effect of velocity on the observed retardation of methylated benzenes is evaluated using three different soils (organic carbon range--0.008% to 0.27%) and a wide range of linear velocities (0.2 ft/day to 40 ft/day). Contaminant solutions of 10 mg/l benzene, toluene, p-xylene and mesitylene, 1 mg/l naphthalene, and 50 mg/l ethylbenzene were pumped through a 0.9 cm ID saturated soil column into a UV/Vis flow-through spectrophotometer for detection of contaminant breakthrough. Breakthrough and flush-out curves, in general, were found to be symmetric, regardless of velocity or contaminant used. Below a velocity of 3 ft/day, compounds with K$\sb{\rm ow}$ values of $>$10$\sp3$ showed an increase in retardation with decreasing velocity. Data were fitted to both an equilibrium and non-equilibrium model with one variable parameter. Results indicated that the data could not be modeled by the non-equilibrium model but did fit the equilibrium model with variable retardation. 105 p. application/pdf eng Environmental science Flow rate effects on the sorption of methylated benzenes in saturated aquifer materials Thesis Text Environmental Science and Engineering Engineering Rice University Doctoral Doctor of Philosophy Clark, Gary Lee. "Flow rate effects on the sorption of methylated benzenes in saturated aquifer materials." (1990) Diss., Rice University. https://hdl.handle.net/1911/16332.
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