Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

First Advisor

Robert P. Gambrell

Abstract

The transport of metals to groundwater below hazardous waste sites is of great environmental concern. The movement of a particular metal is determined by (1) the soil's chemical and physical properties, (2) the amount and form of the metal, and (3) the composition of the soil or waste solution with which the metal is associated. Field and laboratory studies were conducted to examine these factors affecting metal mobility in subsoils. The objectives of the field studies were to determine the distribution and chemical forms of metal contaminants in subsoil at sites with known or suspected potential for groundwater contamination. The objectives of the laboratory studies were to determine the effect of soil properties, solute concentration, solution composition, and redox status on the retention and transport of Cd and Pb in subsoil materials. In the field and laboratory studies, the soil properties controlling Pb retention and mobility were pH, CEC, metal oxides (Mn oxides, amorphous Fe oxides, and free Fe oxides), and soil particle-size distribution. Retention of Cd was controlled by pH, CEC, amorphous Fe oxides, and particle-size distribution. Copper mobility was controlled by the three metal oxides. The Fe oxides (amorphous and crystalline) controlled Ni and Zn retention. Arsenic retention was controlled by pH, CEC, and the metal oxides. Redox potential was also important in Cd and Pb retention, with greater metal retention under oxidizing conditions. In the laboratory studies, higher concentrations of Cd and Pb resulted in lower proportions of metals being retained by the soil. Therefore, the greater the concentration of the metal, the faster it will move through the soil. The retention of Pb was greater than Cd. The retention of Cd and Pb was greater in a dilute salt solution (0.005M Ca(NO$\sb3)\sb2)$ and in a simulated oil field waste. Retention was less in a synthetic municipal landfill leachate and simulated acidic metals waste. Organic complexation of Cd and Pb reduced their retention and thus increased in their mobility. The low pH of the acidic metals waste and competition from other metals reduced Cd and Pb retention in this waste. It was concluded that the composition of the waste solution may override soil factors in controlling trace metal mobility.

Pages

280

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