EPA On-line Tools for Site Assessment Calculation
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Diffusion coefficients, along with other parameters, are required inputs to some environmental transport or risk assessment models. Literature values are sometimes available for these parameters, although, often the literture values are determined at 25 oC. Regulatory programs may have developed preferred sets of parameter values, which should be used if avaialble. Further information on parameter sets is available on the chemical properties page. When parameter values are otherwise unavailable, either for an unusual chemical, or for a temperature not reported in the literature, a calculated value may be useful. Two versions of a calculator for estimating water and air phase diffusion coefficients are available on these pages. The first (this page) contains preset inputs for benzene, toluene, ethylbenzene, and xylenes (BTEX) and oxygenated additives of gasoline. The second version requires generation of input parameters for the chemicals of interest.
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