Selective transport of hydrocarbons in the unsaturated zone due to aqueous and vapor phase partitioning

Water Resources Research



Long-term groundwater contamination can result from vapors and solutes emanating from organic liquids spilled in the unsaturated zone. The mathematical modeling analysis presented in this paper demonstrates for gasoline-range hydrocarbons, and other volatile organics commonly spilled, that diffusive transport in the unsaturated zone is a significant transport mechanism which can cause aqueous and vapor plumes to spread away from the immiscible liquid source, resulting in increasing groundwater contaminating potential. An analytical solution to a one-dimensional version of the transport model allows for the definition of a retardation coefficient which is dependent on phase-partitioning coefficients and moisture content. Significant differences in migration rates should be anticipated between hydrocarbons. A numerical solution was developed for a radially symmetric version of the model defining transport for a multiconstituent contaminant like gasoline. Differences in anticipated migration rates between aromatic and nonaromatic hydrocarbons was clearly demonstrated. A simulation based on the composition of an actual gasoline revealed that aromatic constituents, although constituting a fraction of the initial gasoline composition, completely defined the groundwater contaminating potential. This potential changes in time as constituents are selectively removed from the unsaturated zone. Further, the groundwater contaminating potential is quite sensitive to the ground surface boundary characterization.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Selective transport of hydrocarbons in the unsaturated zone due to aqueous and vapor phase partitioning
Series title Water Resources Research
DOI 10.1029/WR023i010p01926
Volume 23
Issue 10
Year Published 1987
Language English
Publisher American Geophysical Union
Contributing office(s) Toxic Substances Hydrology Program
Description 13 p.
First page 1926
Last page 1938