Subsurface mobile colloids: Their surface characterization, mineralogy, and role in contaminant transport in a coastal plain aquifer

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:7174115

Kaplan, D I

The subsurface environment of the Upper Coastal Plain in the Southeastern US may under certain conditions contain mobile colloids, and that these mobile colloids can facilitate the transport of groundwater contaminants. This hypothesis provoked two main objectives. The first was to characterize mobile colloids and to elucidate some of the conditions conducive to their generation. In a series of studies involving reconstructed, 13.5 m[sup 3], soil profiles collected from the Savannah River Site near Aiken, SC, mobile colloids were found to be enriched in smaller minerals and more dilute in larger minerals as compared to the total clay fraction of the soil. The colloids originated primarily from the surface horizon and had a very large negative charge derived from organic coatings. Soil pH, sodium adsorption ratio, solution ionic strength, and pore water flow rate had an effect on colloid generation. Changes in flow rate also induced changes in colloid mineralogy, size, and surface charge, indicating that the properties of mobile colloids derived from a single source were dynamic. The second objective was to determine the role of colloids in the enhanced transport of contaminants through a surface aquifer impacted by operations on the Savannah River Site. Contaminants were associated with the colloids and this association increased as the pH of the system increased. Detection of Cr, Ni, Cu, and Pb on colloid surfaces by synchrotron X-ray fluorescence microprobe analyses provided direct proof that colloids were transporting these metals. Anions were also transported through the aquifer by colloids. Only a small percentage of the colloids were active in transporting contaminant metals, suggesting that the total amount of colloids may not be as important as the type of colloid in the contaminant transport process. These studies showed that large quantities of mobile colloids can be released from soils of the Southeast and that these colloids can transport contaminants.

• Research Organization: Georgia Univ., Athens, GA (United States)
• OSTI ID: 7174115
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
COLLOIDS
CHEMICAL COMPOSITION
GROUND WATER
POLLUTION
METALS
ENVIRONMENTAL TRANSPORT
SOILS
CHROMIUM
COPPER
LEAD
NICKEL
DISPERSIONS
ELEMENTS
HYDROGEN COMPOUNDS
MASS TRANSFER
OXYGEN COMPOUNDS
TRANSITION ELEMENTS
WATER
540220* - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)