Retention of inorganic pollutants in clayey base sealings of municipal landfills H. Kugler a, * , F. Ottner a , H. Froeschl b , R. Adamcova c , B. Schwaighofer a a Department of Applied Geology, University of Agricultural Sciences Vienna, Peter Jordan Strasse 70, A-1190 Vienna, Austria b Austrian Research Centers Seibersdorf, Chemical Analytics, Arsenal, Faradaygasse 3, 1030 Wien Vienna, Austria c Department of Engineering Geology, Comenius University, Mlynska dolina, 842 15 Bratislava 4, Slovakia Received 28 February 2000; received in revised form 30 January 2001; accepted 16 July 2001 Abstract The 10-year-old base sealing of a municipal waste deposit near Horn, located in the Austrian part of the Bohemian Massif, was examined by mineralogical and geochemical methods. The objective of this study was to measure its retention capability with respect to selected inorganic pollutants, especially heavy metals. The mineralogical results show a homogeneous composition of the base sealing, which consists of clay dominated by kaolinite. In the Bohemian Massif, this pattern is typical for products of weathered rocks, which were originally rich in feldspar. The hydraulic conductivity is very low (k f c 1 Â 10 À 11 ms À 1 ). Geochemical analyses show that heavy metals like Pb, Cu, Zn and Cd are concentrated in the uppermost parts of the sealing. Only a few centimeters below, the concentrations of these elements are at the geochemical background level. Anionic contaminants, however, are found in greater depth due to an almost nonexistent adsorption on the clay. This is the reason why they were used as tracers for further research on diffusion processes (apparent diffusion coefficient of chloride D a,Cl = 2.6 Â 10 À 10 m 2 s À 1 ). Detailed studies of the behavior of Cu, Pb, Zn and Cd were performed using sorption tests (diffusion and batch tests) and sequential extraction methods. From the diffusion experiments, breakthrough times of some heavy metal ions were evaluated for the actual thickness of the sealing. There were Zn > 200 years and Pb > 700 years. These times can be considered as ‘‘worst case’’ examples which give good indications of the retention capability of the sealing. The results clearly demonstrate that even after a period of 10 years of contact with contaminated landfill leachates, the clayey liner had fulfilled the requirements of retaining heavy metals. Furthermore, the base sealing was far from reaching the limits of its retention capacity. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Heavy metals; Pollutants; Transport; Disposal barriers; Diffusion; Landfill 1. Introduction Present societal and waste management policies place capacity limitations on municipal waste depos- its. Therefore, measurements are necessary to monitor and prevent an outlet of contaminants enriched in the leachates. Clay liners at the bottom of the landfill body play a very important part in the whole ‘‘multi- barrier system’’ for retaining pollutants. In the course of remediation of old municipal waste deposit sites a few years ago, such base sealings have been examined. In the case of a landfill near Horn (Lower Austria), the clayey liners had been in contact 0169-1317/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0169-1317(01)00091-6 * Corresponding author. Fax: +43-1-47654-5449. E-mail address: Kugler@edv1.boku.ac.at (H. Kugler). www.elsevier.com/locate/clay Applied Clay Science 21 (2002) 45 – 58