# EPA On-line Tools for Site Assessment Calculation

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#### Effective Solubility of Benzene

Using the example gasoline *"87 Octane gasoline (1) MTBE"* which the note says is a "1996 Long Island OxyFuel (MTBE) gasoline", generates an effective solubility for benzene of 17.0 mg/l. Note that the mass fraction of benzene in this gasoline is less than 1% (0.00703 grams of benzene per gram of gasoline).

If the mass fuel type is switched to "other", the percent mass fraction can be input by the user. Doing this, and experimenting gives an effective solubility of 40 mg/l at a mass fraction of 1.7%

These calculations show that the effective solubility of 40 mg/l is not unreasonable, although it might be somewhat high for contemporary gasolines. But when did the release occur? Older gasolines may have had higher benzene concentrations. |

#### Limitations of the Effective Solubility Calculation

The effective solubility calculated has the following limitations

- a literature fuel composition was used
- the composition of the fuel changes as components are leached out, so the effective solubility may only be an initial value
- the calculator uses an approximation to Raoult's law that assumes
- chemical activity coefficients equal one
- the composition is represented by an average molecular weight

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