Spatial distribution of metal contamination before and after remediation in the Meza Valley, Slovenia Neza Finzgar a , Erika Jez b , David Voglar b , Domen Lestan b, ⁎ a Envit Ltd., Vojkova cesta 63, 1000 Ljubljana, Slovenia b Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia abstract article info Article history: Received 23 September 2013 Received in revised form 19 November 2013 Accepted 25 November 2013 Available online 22 December 2013 Keywords: Metal contamination Geostatistics Empirical Bayesian kriging EDTA extraction Bio-accessibility Geostatistical technique was used to predicted spatial reduction of metal contamination after applying EDTA- based soil remediation. Soil samples from 268 locations in the Meza Valley, Slovenia with Pb and Zn concentra- tions up to 8955 and 15518 mg kg -1 were extracted with the chelating agent ethylenediamine tetraacetate (EDTA). On average, 63 and 22% of Pb and Zn, respectively, were removed with washing solution containing 60 mmol EDTA per kg of soil and 75 and 34% of Pb and Zn with 120 mmol EDTA kg -1 soil. Spatial structure anal- ysis revealed a good spatial structure and little spatial variation of data, which were further interpolated using Empirical Bayesian kriging to produce a continuous surface of Pb and Zn concentrations before and after remedi- ation. Geostatistical simulations showed that the contaminated area covers 19.4 km 2 and that soil remediation (60 mmol EDTA kg -1 ) has the potential to reduce the area with Pb and Zn above the critical regulatory threshold limit by 91 and 42%, respectively. Validated by pilot-scale remediation trials, soil extractions exhibit little scale- dependency of extraction efficiency. EDTA extraction also significantly reduced the bio-accessibility of toxic metals that remained in the soil after remediation using the unified bio-accessibility method. Pb and Zn concen- trations accessible from the simulated intestinal phase were reduced by up to 99 and 96%, respectively. © 2013 Elsevier B.V. All rights reserved. 1. Introduction There is land contamination in most industrialized countries and it is a growing problem in the emerging economies. In China, for example, the land area degraded by mining activities had reached about 3.2 million ha by the end of 2004 and the trend is for this to increase at a rate of 46,700 ha year -1 (Li, 2006). In Europe, the European Environment Agency estimates that there are some 3 million contaminated sites (EEA, 2010). The largest and most affected areas are located in north-west Europe, from the north of France, to Germany, across Belgium and The Netherlands, since these are regions with a high density of urban agglomerations and intensive industrial activities (ESBNEC, 2005). Other regions include the north of Italy and, of the new Member States, Poland and the Czech and Slovak Republics. Most EU Member States have made the clean-up and restoration of the land a priority. One of the most affected locations in Slovenia is the Meza Valley, historically contaminated from Pb mining and smelting, which com- menced in 1665 and continued until 1994. Until the second half of the 19th century, mines and smelters were small and scattered through the valley. A new centralised smelting plant was built in the town of Zerjav in 1893 and Pb production peaked at 27,763 t in 1977. The first systems of filters to decrease dust emissions were installed in 1923 and were further improved in 1954, 1964 and finally in 1978, after which the daily quantity of dust released was reduced from 5000 to 70 kg. During the long history of industrial activities in the Meza Valley, the soil has been the depository of released Pb and also of co-contaminating Zn and it still remains the most significant source of the secondary con- tamination. Indeed, modelling data on Pb concentrations in drinking water, soil, air, dust and vegetables using an integrated exposure uptake biokinetic (IEUBK) model and validation of model results by measured Pb blood concentration data, revealed Pb soil and (soil derived) house dust contamination to be the main environmental factor explaining the measured elevated Pb blood level in children in the Meza Valley (Ivartnik and Erzen, 2010). Effective soil remediation is therefore ur- gently needed. The disposal of contaminated soil and landfill (dig and dump) is costly and heavily restricted, since the EU applies Council Directive (1999/31/EC), which is having a major impact, particularly in Eastern European countries where harmonisation of domestic struc- tures and legislation has become a major priority. Soil capping has been applied on limited areas in the Meza Valley but is not an option for small individually owned plots of land, which predominates. Several remedial approaches to removing toxic metals from Meza soils have also failed: phytoextraction and chemically-induced phytoextraction with various plants and soil extraction with mineral acid were not efficient. The most efficient plant Cannabis sativa phytoextracted 0.6% of the total Geoderma 217–218 (2014) 135–143 ⁎ Corresponding author at: Centre for Soil and Environmental Science, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia. Tel.: +386 1 320 31 62; fax: +386 1 256 57 82. E-mail address: domen.lestan@bf.uni-lj.si (D. Lestan). 0016-7061/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geoderma.2013.11.011 Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma