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SUPERFUND GROUNDWATER ISSUE - FACILITATED TRANSPORT
Citation:
Huling*, S G. SUPERFUND GROUNDWATER ISSUE - FACILITATED TRANSPORT. U.S. Environmental Protection Agency, Washington, DC, EPA/540/4-89/003 (NTIS 91-133256), 1989.
Impact/Purpose:
publish information
Description:
The Regional Superfund Ground Water Forum is a group of ground-water scientists representing EPA's Regional Superfund Offices, organized to exchange up to date information related to ground-water remediation at Superfund sites. Facilitated transport is an issue identified by the forum as a concern of Superfund decision-makers. Any process that has the potential to speed the transport of a pollutant beyond what is expected based solely on considerations of idealized Darcian flow and equilibrium sorptive interactions with an immobile solid phase has been broadly termed, "facilitated transport". Hydrodynamic dispersion, a transport mechanism which fits this description of facilitated transport, is not discussed herein. Research and literature indicates that hydrophobic organic contaminants (HOC's)(i.e., PCB's DDT, dioxins, polynuclear aromatic hydrocarbons (PAH's)) and heavy metals have a high affinity for mobile subsurface particles and that such an attraction may alter the mobility of the contaminant. Facilitated transport is a relatively new area of study in the field of contaminant transport. Considerable research and interest is currently focused in this area. Although incompletely understood at this point, the effects of facilitated transport at Superfund sites may range from paramount to negligible. There may be an abundance of field data currently available that identifies both the occurrence and the importance of these transport mechanisms. However, relatively little information is available in the scientific literature which attempts to correlate the occurrence of these transport mechanisms with field data. Most Superfund Sites are characterized as having the following conditions: a complex misture of organic and inorganic wastes; highly variable chemical and physical characteristics; a broad range of chemical concentrations; and a broad spectrum of soil and hydrogeological characteristics. Therefore, several facilitated transport mechanisms may be occurring simultaneously at any site. Idealized laboratory experimentes reported in the literature have been designed to simulate specific physical and chemical conditions. These laboratory conditions have allowed researchs to control the variables which affect the behavior of contaminants in the subsurface and to identify the mechanisms wich are likely to occur in the field. An understanding of the various mechanisms of facilitated transport will provide a more thorough understanding of the fate and transport of contaminants in the ground water and ultimately will provide the framework for further development of ground-water remediation technology.