Chemical Property Values
Partitioning of chemicals between environmental media (water, air, soil) are partly determined by properties of the chemicals themselves. Values of these properties often can be obtained from the scientific literature that reports on measured values. Since there are a wide range of environmental conditions of interest (especially temperature and pH), there are often no suitable literature values available. In these cases, estimated parameters can be determined through a variety of methods. A reference on methods is Boethling, R.S. and D. MacKay, 2000, Handbook of Property Estimation Methods for Chemicals, CRC Press, Boca Raton, Florida.
Sources of both measured and estimated values are listed below.
Measured Values
Data compilations
Each of these three compilations give reported values from several sources and in some cases recommended values. These links exit the EPA Web site.
- Search for Species Data National Institute of Standards and Technology
- Chemical and Physical Properties Database Pennsylvania Land Recycling Program
- CHEMFATE Chemical Search Syracuse Research Corporation
Database of parameters in use by State and Federal Agencies
Preferred values of chemical properties have been compiled by State and Federal Agencies for use in environmental programs. The lists are developed by a variety of methods, but in some cases provide a standardized set of property values for use in the state or environmental program. EPA is currently developing a compilation of these properties that will be available from this page.
Estimates
A general purpose calculator has been developed for situations where suitable measured values are not available. Examples include newly-developed chemicals, those that have had little environmentally related data collection, or where chemical parameters are not available at an environmentally relevant temperature or pH. The calculator is called SPARC Performs Automated Reasoning in Chemistry (SPARC)
and was jointly developed by US EPA and the University of Georgia.
A set of SPARC-generated parameters (Vapor Pressure, Activity Coefficients, Vapor Pressures and Henry's Constants) are available for petroleum hydrocarbons and oxygenated additives that resulted from detailed hydrocarbon analysis of U.S. gasolines.
Calculators designed for specific properties or chemical classes give the better estimates for those conditions, but have a limited applicability.
- Henry's law estimation
- Diffusivity in air and water
- Koc from Kow
- Estimation Program Interface (EPI) Suite
Other closely-allied calculations are made from chemical properties, including:
- Retardation factor in ground water
- Effective solubilities of fuel components
- Multiphase partitioning
- Henry's law unit conversions
- Conversions between half lives and decay constants