title: Effects of the buffering capacity of the soil on the mobilization of heavy metals. Equilibrium and kinetics.
abstract: Understanding the possible pH-buffering processes is of maximum importance for risk assessment and remediation feasibility studies of heavy-metal contaminated soils. This paper presents the results about the effect of the buffering capacity of a polluted soil, rich in carbonates, on the pH and on the leaching evolution of its main contaminant (lead) when a weak acid (acetic acid) or a strong one (nitric acid) are slowly added. In both cases, the behavior of lead dissolution could be predicted using available (scientifically verified freeware) models assuming equilibrium between the solid and the aqueous phase. However, the experimental results indicate that the dissolution of calcium and magnesium carbonates is kinetically controlled. These kinetic limitations affect the overall behavior, and should be considered to understand also the response of the metals under local equilibrium. The well-known BCR sequential extraction procedure was used before- and after-treatment, to fractionate the lead concentration in the soil according to its mobility. The BCR results were also in agreement with the predictions of the equilibrium model. This agreement allows new insights about the information that could be derived from the BCR fractionation analysis.
authors.affiliation: Chemical Engineering Department, University of Malaga, 29071 Malaga, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Villen-Guzman
authors.affiliation: Division of Solid Mechanics, Lund University, Lund, Sweden.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Paz-Garcia
authors.affiliation: Chemical Engineering Department, University of Malaga, 29071 Malaga, Spain.
authors.forename: Gema
authors.initials: G
authors.lastname: Amaya-Santos
authors.affiliation: Chemical Engineering Department, University of Malaga, 29071 Malaga, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Rodriguez-Maroto
authors.affiliation: Chemical Engineering Department, University of Malaga, 29071 Malaga, Spain. Electronic address: cvereda@uma.es.
authors.forename: Carlos
authors.initials: C
authors.lastname: Vereda-Alonso
authors.affiliation: Chemical Engineering Department, University of Malaga, 29071 Malaga, Spain.
authors.forename: Cesar
authors.initials: C
authors.lastname: Gomez-Lahoz
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D002021:Buffers; D002254:Carbonates; D005591:Chemical Fractionation; D004787:Environmental Pollution / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019216:Metals, Heavy / Q000032:analysis / Q000302:isolation & purification*; D008962:Models, Theoretical; D017942:Nitric Acid / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000302:isolation & purification*; D012995:Solubility
chemical_list: D002021:Buffers; D002254:Carbonates; D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D017942:Nitric Acid; D019342:Acetic Acid
keywords: Buffering capacity; Heavy metal; Kinetic limitations; Lead; Sequential extraction procedure