This research aims to investigate clay soil absorption abilities on contaminant through laboratory test. The method presented in the paper differs from conventional ASTM (1993) standard, which may overestimate the soil absorption as indicated in the previous studies. To complete the purpose, four types of Kyushu regional soils were selected in Japan, and three kinds of synthetic contaminant were employed. With the application of the entitled specific term, contaminant absorption ratio introduced in the paper, it is found that Ariake clay possesses higher absorption ability as compared with other tested soils. This should be due to its high cation exchange capacity and illite mineral content as well.
Now clay-rich geological materials are often used as barriers to the migration of potential contaminant from waste disposal sites. Recent studies have shown that where the clay barrier has a very low hydraulic conductivity or negligible hydraulic gradient, advective component will be very low (Goodall and Quigley, 1977; Desaulniers et al., 1981, 1984; Cooks and Quigley, 1984; Quigley et al., 1984; Johnson et al., 1986; Rowe et al., 1988; Shackelford and Daniel, 1991), and controlled by diffusion through pore fluid. The principal controlling parameters for diffusive transport including diffusion coefficient and geochemical reactions, such as absorption, precipitation, and desorption. Those parameters depend on the clay mineralogy, pore water composition, solute species of interest, ionic strength and biological factors. A comprehensive discussion of these parameters and their significance in terms of contaminant transport, can be found in references such as Ellis et al. (1970), Barraclough and Tinker (1961), Gupta and Deb (1982), Mullins and Summers (1986), Rowe et al. (1988), and Shackelford and Daniel (1991). Conventional ASTM (1993) has provided the standard method to evaluate the absorption abilities of the clay soil on contaminant.