Please cite this article in press as: M.A. Lilli, et al., Characterization and mobility of geogenic chromium in soils and river bed sediments of Asopos basin, J. Hazard. Mater. (2014), http://dx.doi.org/10.1016/j.jhazmat.2014.07.037 ARTICLE IN PRESS G Model HAZMAT-16130; No. of Pages 8 Journal of Hazardous Materials xxx (2014) xxx–xxx Contents lists available at ScienceDirect Journal of Hazardous Materials j o ur nal ho me pa ge: www.elsevier.com/locate/jhazmat Characterization and mobility of geogenic chromium in soils and river bed sediments of Asopos basin Maria A. Lilli a,∗ , Daniel Moraetis b , Nikolaos P. Nikolaidis a , George P. Karatzas a , Nicolas Kalogerakis a a Technical University of Crete, Department of Environmental Engineering, University Campus, 73100 Chania, Greece b Sultan Qaboos University, Science College, Earth Science Department, Oman h i g h l i g h t s • Surface agricultural soils and river sediments were geochemically characterized. • Soil and sediments were classified into 3 classes with respect to the origin of Cr. • Geogenic chromium is present in Asopos soils and river bed sediments. • The mobility of Cr is controlled by ferric oxides surface complexation. a r t i c l e i n f o Article history: Received 18 January 2014 Received in revised form 5 July 2014 Accepted 18 July 2014 Available online xxx Keywords: Hexavalent chromium Geogenic chromium Soil/sediment characterization Mobility a b s t r a c t A field and laboratory study was conducted to assess the origin and mobility of CrVI in Asopos basin in Greece. Sampling was designed in such way as to capture the spatial variability of chromium occur- ring in sediments and soils in different lithological units in the area. Physicochemical and geochemical characterization of surface agricultural soils obtained from river terraces and river bed sediments was conducted in order to determine the natural background of chromium. Lithologies with strong calcare- ous, siliceous and ultramafic components were identified using principal component analysis. Laboratory mobility studies quantified the rates of chromium sorption and release from soils and their capacity to adsorb chromium. Heavy metal analysis and local geology study support the hypothesis that the main source of chromium is of geogenic origin. Chromium distribution in Asopos river bed was influenced from the eroded products derived from extensive areas with ultramafic rocks the last 5 Ma. The mobility studies showed that leaching process was very fast and sorption capacity was significant and capable to retain chromium in case of waste release in the river. Finally the mobility of chromium release is limited due to existing attenuation capacity controlled by ferric oxides coatings on the soil and sediments. © 2014 Elsevier B.V. All rights reserved. 1. Introduction A growing worldwide concern on human health risks of chromium has stimulated research on its fate and transport in groundwater [1]. In the environment, Cr is found mainly in two oxidation states, the trivalent Cr(III) and the hexavalent Cr(VI). Hexavalent Cr is mobile and highly toxic for humans, whereas Cr(III) is immobile, has low toxicity and is considered to be an essential trace element in human metabolism. The differences of the two oxidation states of chromium make the assess- ment of potential human health risks, difficult [2]. The European ∗ Corresponding author. Tel.: +30 2821037784; fax: +30 2821037846. E-mail address: marialilli02@gmail.com (M.A. Lilli). Commission (Directive 98/83/EC) established 50 g/L as the maxi- mum permissible limit of total chromium in drinking water, similar to the one established by the World Health Organization. The Italian regulation defined a maximum allowable concentration of 2 mg/L (on a dry basis) for Cr(VI) in soils for private use, and a maximum acceptable concentration of 150 mg/L for total Cr [3]. The processes of chromium release from soils and adsorption to soils has been the subject of significant body of research and the understanding of the mechanisms affecting chromium fate in aquifers (oxidation, reduction, adsorption and desorption) is of paramount importance [4]. The kinetics of the chromium redox reactions complicate chromium transport because each chromium species presents a different sorptive behavior depending on the prevailing physicochemical conditions (e.g. pH, organic matter con- tent) [5]. Transport of chromate is mainly controlled by adsorption http://dx.doi.org/10.1016/j.jhazmat.2014.07.037 0304-3894/© 2014 Elsevier B.V. All rights reserved.