title: The performance of natural clay as a barrier to the diffusion of municipal solid waste landfill leachates.
abstract: In this paper, the diffusion of solutes in natural clay from a concentrated solution consisting primarily of ammonium, sodium and chloride ions at a pH level of 8 was studied and was based on an existing 20-year-old landfill. Contaminant transport through clay liners was predicted using transport and reaction geochemical codes to help explain the experimental data. The model predicted the chloride anion diffusion and cation exchange processes for three different experiments: (1) small-scale interactions in compacted clay, (2) 1:1 European Union (EU) Directive demonstration experiments (0.5-m-thick clay barrier), and (3) analysis of a bore hole with core recovery drilled in an old landfill located above a similar type of clay as that studied in (1) and (2). Orders of magnitude between 10(-10) and 10(-9) m(2) s(-1) were used for the apparent diffusion coefficient to fit the chloride profiles at the different scales; however, at larger space and time scales, diffusion was retarded due to the presence of more consolidated, non-mechanically disturbed clay materials at large depths in a natural clay-rock emplacement.
authors.affiliation: Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, Facultad de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Cuevas
authors.forename: Ana I
authors.initials: AI
authors.lastname: Ruiz
authors.forename: Isabel S
authors.initials: IS
authors.lastname: de Soto
authors.forename: Teresa
authors.initials: T
authors.lastname: Sevilla
authors.forename: Jesús R
authors.initials: JR
authors.lastname: Procopio
authors.forename: Pilar
authors.initials: P
authors.lastname: Da Silva
authors.forename: Ma Jesús
authors.initials: MJ
authors.lastname: Gismera
authors.forename: Mercedes
authors.initials: M
authors.lastname: Regadío
authors.forename: Nicanor
authors.initials: N
authors.lastname: Sánchez Jiménez
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodríguez Rastrero
authors.forename: Santiago
authors.initials: S
authors.lastname: Leguey
mesh_terms: D000538:Aluminum Silicates; D002712:Chlorides / Q000737:chemistry; D000077215:Clay; D004058:Diffusion; D005062:European Union; D017408:Guidelines as Topic; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012037:Refuse Disposal / Q000379:methods*; D012964:Sodium / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D002712:Chlorides; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D012964:Sodium; D000077215:Clay