Date of Award
1990
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
A laboratory diffusion test determination of diffusion coefficient (D) and adsorption coefficient (K{dollar}\sb{lcub}\rm d{rcub}{dollar}) for various inorganic and organic species in a saturated, undisturbed, clayey soil is presented. Diffusion tests conducted for inorganic species (Cl{dollar}\sp-{dollar}, Na{dollar}\sp+{dollar}, K{dollar}\sp+{dollar}, Mg{dollar}\sp{lcub}2+{rcub}{dollar}, and Ca{dollar}\sp{lcub}2+{rcub}{dollar}), involved placing domestic landfill leachate on top of a layer of clay and allowing the chemical constituents to diffuse into the soil. The mathematical model "POLLUTE" was then used to back-figure (D) and (K{dollar}\sb{lcub}\rm d{rcub}{dollar}) for each species by fitting: (1) the variation in species concentration with time in the source leachate, and (2) the variation in pore water concentration with depth in the soil layer at the end of the test. Similar tests using a single salt dissolved in distilled water as the source solution, indicated that both D and K{dollar}\sb{lcub}\rm d{rcub}{dollar} of a given species are significantly influenced by the types and amounts of co-diffusing species present in the initial source solution.;Diffusion tests conducted for organic species (acetone, 1,4-dioxane, aniline, chloroform, and toluene), involved diffusion of the species from a source solution placed on one side of a clay plug, into a distilled water collector solution on the opposite side. Using POLLUTE, D and K{dollar}\sb{lcub}\rm d{rcub}{dollar} were then determined by fitting the measured concentration variation with time in both the source and collector solution. The test gave good results for the more soluble species: acetone, 1,4-dioxane, and aniline. The more hydrophobic species (chloroform and toluene), however, gave high D and K{dollar}\sb{lcub}\rm d{rcub}{dollar} values, partly due to adsorption of the species onto the walls of the diffusion cell.;In addition to the laboratory study, an investigation of inorganic contaminant diffusion below an existing industrial landfill site was conducted by analyzing soil and pore water specimens from the clay layer underlying the waste. Concentration profiles for Cl{dollar}\sp-{dollar}, So{dollar}\sb4\sp{lcub}2-{rcub}{dollar}, Na{dollar}\sp+{dollar}, Ca{dollar}\sp{lcub}2+{rcub}{dollar} and Mg{dollar}\sp{lcub}2+{rcub}{dollar}, showed above background levels to a depth of 1.4 m below the waste after 11 years of migration. K{dollar}\sp+{dollar}, B, and NH{dollar}\sb3{dollar}-N profiles, penetrated to less than 0.5 m below the waste. Field profiles for Na{dollar}\sp+{dollar}, K{dollar}\sp+{dollar}, Cl{dollar}\sp-{dollar}, and SO{dollar}\sb4\sp{lcub}2-{rcub}{dollar} were then compared with those predicted using POLLUTE with D and K{dollar}\sb{lcub}\rm d{rcub}{dollar} values obtained from diffusion tests using leachate and natural uncontaminated clay from the site. By assuming simple boundary conditions such as a constant source concentration, calculated profiles overestimated the upper part of the measured concentration profile, but reasonably predicted the depth of penetration.;Finally, a laboratory diffusion test determination of Cl{dollar}\sp-{dollar} diffusion coefficient in samples of intact, saturated shale and mudstone is presented. These tests were performed by placing distilled water in contact with core samples having a high initial Cl{dollar}\sp-{dollar} concentration. Chloride was then permitted to diffuse out of the sample and into the distilled water. At the end of the test the sample was sectioned, and the Cl{dollar}\sp-{dollar} profile measured. Provided that there is no significant moisture uptake from the distilled water reservoir, the diffusion profile developed could be adequately fitted using POLLUTE, and the diffusion coefficient determined.
Recommended Citation
Barone, Frank S., "Determination Of Diffusion And Adsorption Coefficients For Some Contaminants In Clayey Soil And Rock: Laboratory Determination And Field Evaluation" (1990). Digitized Theses. 1990.
https://ir.lib.uwo.ca/digitizedtheses/1990