Ecosystems Research

EPA On-line Tools for Site Assessment Calculation

Module Home Objectives Table of Contents Previous < Next >

34 of 45

Bulk Density Result

With porosity of 0.35, the bulk density is 1.72 g/cm³. This contrasts with the value of 2.65 g/cm³ used in the report. The value of 2.65 g/cm³ 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

Bulk Density

where r_b is the bulk density, r_s is the solid density (2.65 g/cm³, 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 chemical-specific property, the organic carbon partition coefficient, K_oc and an aquifer-specific property, the fraction organic carbon, f_oc.

The calculation is made from the formula:

Retardation factor definition

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 site-specific 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.

Again use the retardation factor calculator with values of f_oc of 0.0001, porosity of 0.35, and benzene as the chemical. Enter these values (or press the recall button) in the retardation factor calculator, and find the retardation factor by pressing the calculate button. When finished, use the calculator "Go Back" button to return..

To see how much difference the f_oc value makes, rerun the calculation with the value of 0.001.

Previous Top ^ Next

EPA On-line Tools for Site Assessment Calculation

Bulk Density Result

Sorption and Fraction Organic Carbon

Area Navigation