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Bulk Density Result
With porosity of 0.35, the bulk density is 1.72 g/cm^{3}. This contrasts with the value of 2.65 g/cm^{3} used in the report. The value of 2.65 g/cm^{3} is the solid density of quartz, a value that you should remember. 
The bulk density is the density of a unit volume of the aquifer that includes the solids and the void space. Thus the bulk density must be lower than the solid density, as it is defined by
where r_{b} is the bulk density, r_{s} is the solid density (2.65 g/cm^{3}, and q is the porosity.
Sorption and Fraction Organic Carbon
The amount of sorption is usually determined from the use of a retardation factor. The retardation factor depends on a chemicalspecific property, the organic carbon partition coefficient, K_{oc} and an aquiferspecific property, the fraction organic carbon, f_{oc}.
The calculation is made from the formula:
where R is the retardation factor, r_{b} is the bulk density, and q is the porosity.
K_{oc} is normally obtained from the literature, and f_{oc} from a sitespecific measurement, but was not reported for this site. Geologists familar with the formation indicated, however, that an f_{oc} of 0.0001 would be reasonable, because the aquifer consists of a clean sand.


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