Determination of transport parameters for heavy metal in residual compacted soil using two methodologies

Abstract

Values of the hydrodynamic dispersion coefficient and retardation factor obtained using the traditional and cumulative mass methods of column test analysis for zinc, manganese, and cadmium in a compacted soil are compared. The soil under study is from the B horizon of a residual gneissic tropical soil used for construction of the liner for the sanitary landfill in the District of Visconde do Rio Branco, Minas Gerais (MG), Brazil. To evaluate the behavior of landfill leachate heavy metals through the soil, soil column tests were performed on samples of compacted soil. A computational program that uses an optimization procedure to generate values of the hydrodynamic dispersion coefficient and retardation factor was developed to facilitate interpretation of the results obtained by the cumulative mass method. Values of the retardation factor and hydrodynamic dispersion coefficient were not influenced by the method of determination, even when a reduced number of effluent samples was used by the cumulative mass method. The use of the cumulative mass method, based on a reduced number of pore volumes, reduces the time and cost involved in the tests.Key words: heavy metals, column test, cumulative mass method.

Variation in Hydraulic Conductivity by the Mobility of Heavy Metals in a Compacted Residual Soil

“…It is thus possible to conclude that Zn and Cd replaced the desorbed Mn on the soil adsorption sites. A Mn retardation factor of 18.8 was reported by Azevedo et al (2005), close to the average value presented in Table 6. Given the greater hydraulic conductivity values (10 -5 to 10 -6 cm s -1 ) in the work by Azevedo et al (2005) as compared to those in the present study (10 -6 to 10 -7 cm s -1 ), the mobility of Mn was found to be practically independent of soil hydraulic conductivity.…”

“…The fact that the leachate pH value remained above that of the influent solution may be due to the fact that ion exchange of metals by the bases adsorbed in the soil solid phase continued over the course of the test. It is believed that when sample saturation with all the metals is reached the leachate pH will tend to equal the influent pH, as was observed by Azevedo et al (2005). Cation leaching occurred due to substitution by heavy metals added to the soil.…”

Correlation between diffusion coefficient values of chloride ions obtained through column and ion migration tests in cementitious matrices with varying contents of silica fume and mortar

“…The column test aims to determine the transport parameters that interfere with the diffusion of contaminants by porous media in controlled laboratory conditions [6], [29] which reflect the real situation. This technique is extensively used to understand soil/contaminant interaction, but recently it has been applied in Portland cement matrices, such as soil-cement [13] and in mortars and concrete [12].…”

Geo-Environmental Site Investigation for Municipal Solid Waste Disposal Sites

“…In Brazil, most of the laboratory tests for sanitary landfills are preventive, for bottom or cover liner design, using low permeability compacted tropical soils with or without flexible membrane liners (Ritter, 1998;Boscov et al, 2001;Leite & Paraguassú, 2002;Stuermer, 2005;Azevedo et al, 2006). This approach does not consider the older waste deposits, where the contaminants are in direct contact with the natural subsoil.…”