title: Equilibrium leaching of toxic elements from cement stabilized soil.
abstract: The toxicity characteristics leaching procedure (TCLP) is commonly used to assess the efficiency of solidification/stabilization (S/S) of pollutants in wastes, despite recent objections to this method. In this study, formulations of 7, 10, 15 and 20% (w/w) of calcium aluminate cement (CAC) and sulfate resistant Portland cement (SRC) were used for S/S of soil from brownfield contaminated with 43,149, 10,115, 7631, 6130, 90, 82 mg kg(-1) of Zn, Pb, Cu, As, Cd and Ni, respectively. CAC produced S/S soil monoliths of higher mechanical strength (up to 7.65 N mm(-2)). Mass-transfer analysis indicated surface wash-off as a mechanism of toxic elements release, and equilibrium leaching as a crucial parameter of S/S efficiency assessment. In the expected range of field soil pH after S/S (pH 7-9), the TCLP gave markedly different results than the multi-point pH equilibrium leaching method (using nine targeted pH values): up to 2953-, 94-, 483-, 1.3-, 27- and 1.5-times more Zn, Pb, Cu, As, Cd and Ni, respectively, was determined in the TCLP leachate. S/S with CAC reduced leachability of toxic elements more effectively than SRC. Our results indicate that, under given field conditions, the TCLP significantly underrates the efficiency of S/S of contaminated soil with cementitious binders.
authors.affiliation: RDA - Regional Development Agency Celje, Kidričeva ulica 25, 3000 Celje, Slovenia.
authors.forename: Grega E
authors.initials: GE
authors.lastname: Voglar
authors.forename: Domen
authors.initials: D
authors.lastname: Leštan
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000737:chemistry*; D005240:Feasibility Studies; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D012989:Soil Pollutants
chemical_list: D019216:Metals, Heavy; D012989:Soil Pollutants; D001151:Arsenic