50 years of different landscape management influencing retention of metals in soils Vladislav Chrastný a, b, ⁎, Michael Komárek b , Jan Procházka c , Libor Pechar c , Aleš Vaněk d , Vít Penížek d , Juraj Farkaš b a Czech Geological Survey, Geologická 6, 155 00 Prague 5, Czech Republic b Czech University of Life Sciences Prague, Faculty of Environmental Sciences, Kamýcká 129, 165 21 Prague 6, Czech Republic c University of South Bohemia, Faculty of Agriculture, Studentská 13, 370 05, České Budějovice, Czech Republic d Czech University of Life Sciences Prague, Faculty of Agrobiology, Food and Natural Resources, Kamýcká 129, 165 21 Prague 6, Czech Republic abstract article info Article history: Received 14 October 2011 Accepted 23 February 2012 Available online 3 March 2012 Keywords: Landscape management Soils Retention Metals Sequential extraction The geochemical position of metals bound to soils in an area with 50 years of different landscape manage- ment practices (land use) during its unique historical development has been studied in this work. The three following localities were chosen for study: (i) afforested area, (ii) wetlands and (iii) pasture. Small changes in the soil physico-chemical properties have been detected between the studied catchments, however, significant differences in the geochemical position of metals were found in the upper soil horizons. Metals, e.g., Cr, Co, Ni, Cu, Zn, Pb and Tl are present mainly in non-residual forms in the forest organic soil horizons while in the pasture soils the predominant metal form is residual. It was demonstrated that soil organic matter (SOM) is responsible for metal retention in soils. Pasture soils with a lower amount of solid SOM are not able to retain the metals efficiently in the upper soil horizons. Therefore, these soils are much more vulnerable to possible anthro- pogenic contamination. The different landscape management types/practices did not influence the metal forms in deeper soil horizons because the metal distribution in the mineral soil horizon did not differ within the studied localities. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Factors influencing the metal mobility and bioavailability in soils include: temperature, redox potential, cation exchange capacity of soil solid phase (CEC), competition with other metal ions, ligation by anions, composition and quantity of the soil solution and particularly soil pH. For metal uptake at least two factors have a direct impact, (i) soil pH and (ii) the content of organic matter (Andersen et al., 2004; Strobel et al., 2001, 2005). Different land uses (wetlands, grasslands and afforestation) can change the soil structure and physico-chemical soil properties and can then directly or indirectly influence the geochemical position of metals bound to soils. The study carried out in wetlands showed that the flooding process increased mobility of Fe, Mn, Ni and Cr as opposed to Cd, Cu and Zn. The mobilization is controlled by the changes in chemical compositions of Fe, Mn-oxyhydroxides, decom- position of carbonates, formation and re-oxidation of sulfides etc. (Du et al., 2008). Plant biomass also seems to be an efficient agent in affecting the metal mobility. Afforestation of cultivated agriculture soils change the geochemical position of metals by the processes of soil acidification and the release of dissolved organic carbon (DOC) into soils and soil solution (Andersen et al., 2004; Strobel et al., 2001, 2005). Tree species affect soil characteristics e.g., pH and soil or- ganic matter (SOM) content in topsoil while they do not affect deeper soil horizons. The mechanism of affecting the soil parameters is relat- ed to the production of litter with different chemical compositions and degradability and therefore influences the chemical composition of DOC in soil solution (Strobel et al., 2001). Several tree species con- tributed to the acidification of soils to different extents. The soils under Norway spruce embodied a higher acidification effect than beech and oak and the amount of SOM was higher as well (Andersen et al., 2004; Strobel et al., 2001). The forest floor layer can serve as a pool for metals due to the high amount of SOM (Ermakov et al., 2007). The Pb from anthropogenic sources being introduced to soils is adsorbed mainly at the surface of SOM. The consequent process of decomposition and SOM dissolu- tion influences speciation of metals bound to organic soil horizons. After decomposition of SOM lead was redistributed to pedogenic bir- nessite and ferrihydrite and thus is immobilized (Schroth et al., 2008). On the other hand, a higher amount of organic matter can re- strict the solubility of Cu, Pb and Sb (Clemente et al., 2008) but it de- pends on the structure of SOM and the pH of soil solution (Andersen et al., 2004; Songhu et al., 2007; Strobel et al., 2001). Soluble organic acids present in the rhizosphere can mobilize Cd, Zn, Pb (Schwab et al., 2008). Organic matter (sewage sludge compost) added to soils can increase Pb concentration in soil solution while Cu is immobilized through the formation of complexes (organic and sulfides) with low mobility (Brazauskiene et al., 2008). Journal of Geochemical Exploration 115 (2012) 59–68 ⁎ Corresponding author. Tel.: + 420 725 561 330; fax: + 420 251 818 748. E-mail address: vladislav.chrastny@geology.cz (V. Chrastný). 0375-6742/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2012.02.007 Contents lists available at SciVerse ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/jgeoexp