Adsorption of a Pollutant from Groundwater onto Soil

Illustration 6.5 Adsorption of a Pollutant from Groundwater onto Soil 

Soils show a considerable sorptive affinity for pollutants that is principally brought about by the soil s carbon content (a result of decaying organic matter). That content typically ranges from 1 to 2% of the total mass. Adsorptive capacities per unit weight are consequently some 50 times lower than the carbon values shown in Table 6.4, and this figure was used to compose the Table 6.5 listing of Henry s constants for soils. 

We consider here again an effluent saturated with benzene and assume that seepage into the groxmdwater has occurred. The task will be to calculate the stretch of soil that will have been contaminated after 10 days of exposure. Groundwater velocity is set at 1 mm/s and soil density at 2500 kg/m. Using a Henry s constant of 0.54 given in Table 6.5, we obtain from Equation 6.7a 

Henry s Constants for Aqueous Solutions on Soil at 25dC 

Note that the rigorous PDF model would require, in addition to equilibrium data, the relevant transport parameter, i.e., the mass transfer coefficients within both the solid particle and the liquid. The solid-phase coefficient, in particular, requires fairly elaborate measurements and is usually unavailable to the general practitioner. 

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