Removal of trace elements from landfill leachate by calcite precipitation Vojte ˇch Ettler a, * , Olga Zelena ´ a , Martin Mihaljevic ˇ a , Ondrˇej S ˇ ebek b , Ladislav Strnad b , Pavel Coufal c , Petr Bezdic ˇka d a Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic b Laboratories of Geological Institutes, Charles University, Albertov 6, 128 43, Praha 2, Czech Republic c Department of Analytical Chemistry, Charles University, Hlavova 2030/8, 128 43, Praha 2, Czech Republic d Institute of Inorganic Chemistry, Academy of Science of the Czech Republic, 250 68 R ˇ ez ˇ, Czech Republic Received 29 March 2005; accepted 19 August 2005 Available online 25 October 2005 Abstract Spontaneous precipitation of secondary calcite (CaCO 3 ) has been observed in 25 samples of landfill leachate-polluted stream waters. During the 6-month precipitation experiment, the formation of calcite acts as a principal trace-element scavenging process. The concentrations of Fe, Sr, Ba and Mn and other trace elements in solution significantly decreased as calcite formed during the experiments. The PHREEQC-2 geochemical code indicated high supersaturation of the initial leachate-polluted waters with respect to calcite. The chemical/mineralogical study (SEM/EDS, XRD, ICP MS) revealed that this newly formed calcite contains considerable amounts of metals and metalloids removed from solution. Such a geochemical process can be considered to be important for spontaneous decontamination in landfill-affected environments (stream sediments, soils) or landfill technical facilities (settling basins). This removal takes place especially during dry periods with low rain precipitation, when the landfill waters exhibit both higher alkalinity and higher trace element concentrations. D 2005 Elsevier B.V. All rights reserved. Keywords: Landfill leachate; Calcite; Scavenging; Trace elements; PHREEQC-2 1. Introduction Metals and other trace elements are present in municipal waste landfill leachates in considerable concentrations (Baun and Christensen, 2004). The long-term leakage of landfill leachate into ground- or surface waters may locally be of environmental concern (Ettler et al., 2003). The landfill leachates also exhibit high alkalinity, caused by biodegradation processes in the body of the landfill (Manning, 2001). As a result, leachates are commonly supersaturated with respect to calcite that has been observed to pre- cipitate at numerous landfill sites (Manning, 2001; Ettler et al., 2003). In this study we present geochemical/mineralogical evidence for the effect of calcite precipitation on removal of trace elements from landfill leachate-polluted waters. Long-term spontaneous precipitation experiments of cal- cite in leachate-polluted water were coupled with trace element analysis (ICP MS), thermodynamic speciation- solubility modelling (PHREEQC-2) and mineralogical investigation of newly formed calcite. 0375-6742/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2005.08.010 * Corresponding author. Tel.: +420 221 951 493; fax: +420 221 951 496. E-mail address: ettler@natur.cuni.cz (V. Ettler). Journal of Geochemical Exploration 88 (2006) 28 – 31 www.elsevier.com/locate/jgeoexp