Pollution profiles and physicochemical parameters in old uncontrolled landfills |
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Authors: | Regadío M Ruiz A I de Soto I S Rastrero M Rodriguez Sánchez N Gismera M J Sevilla M T da Silva P Procopio J Rodríguez Cuevas J |
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Institution: | a Department of Geology and Geochemistry, Faculty of Science, Autónoma University of Madrid, Campus Cantoblanco, C/Fco. Tomás y Valiente 7, 28049 Madrid, Spain b Department of Analytical Chemistry and Instrumental Analysis, Faculty of Sciences, Autónoma University of Madrid, Campus Cantoblanco, C/Fco. Tomás y Valiente 7, 28049 Madrid, Spain |
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Abstract: | The long-term effectiveness of the geological barrier beneath municipal-waste landfills is a critical issue for soil and groundwater protection. This study examines natural clayey soils directly in contact with the waste deposited in three landfills over 12 years old in Spain. Several physicochemical and geological parameters were measured as a function of depth. Electrical conductivity (EC), water-soluble organic carbon (WSOC), Cl−, NH4+, Na+ and exchangeable NH4+ and Na+ were used as parameters to measure the penetration of landfill leachate pollution. Mineralogy, specific surface area and cationic-exchange capacities were analyzed to characterize the materials under the landfills. A principal component analysis, combined with a Varimax rotation, was applied to the data to determine patterns of association between samples and variables not evident upon initial inspection. The main factors explaining the variation in the data are related to waste composition and local geology. Although leachates have been in contact with clays for long time periods (13-24 years), WSOC and EC fronts are attenuated at depths of 0.2-1.5 m within the clay layer. Taking into account this depth of the clayey materials, these natural substrata (>45% illite-smectite-type sheet silicates) are suitable for confining leachate pollution and for complying with European legislation. This paper outlines the relevant differences in the clayey materials of the three landfills in which a diffusive flux attenuation capacity (Ac) is defined as a function (1) of the rate of decrease of the parameters per meter of material, (2) of the age and area of the landfill and (3) of the quantity and quality of the wastes. |
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Keywords: | Ac attenuation capacity CEC cationic-exchange capacity DS dissolved solids EC electrical conductivity Ex_cation exchangeable cation h moisture K hydraulic conductivity LMMOAs low-molecular-mass organic acids PC principal component PCA principal component analysis Rd ratio decrease per metre deep of parameter X averaged per landfills Sol_ion soluble ion SSA specific surface area WSIC water soluble inorganic carbon WSOC water soluble organic carbon |
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