177 Factors controlling major ion and trace element content in surface water at Asprolakkas hydrological basin, NE Chalkidiki: Implications for elemental transport mechanisms E. Kelepertzis 1 , A. Argyraki, E. Daftsis 1 Corresponding author: Section of Economic Geology and Geochemistry, Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimiopolis, Zographou 157 84, e-mail: kelepert@geol.uoa.gr Abstract Chemical characteristics of stream water at Asprolakkas hydrological basin were determined in February 2009 in order to examine the main factors con- trolling the hydrogeochemistry of the drainage system. A total of 20 surface water samples were collected and analyzed for the major ions K, Na, Ca, Mg, HCO 3 , SO 4 and the trace elements Fe, Pb, Zn, Mn, Cu, Ni, As, Sb, Mo and Ba. The appli- cation of R-mode factor analysis revealed that the polymetallic carbonate re- placement type sulfide deposits, together with the porphyritic intrusions and the associated porphyry copper style mineralization, occurring in the studied area, im- pose fundamental control on the water chemistry. A third influencing factor in- cludes the parameters As and HCO 3 and is attributed to the competitive behavior of As and bicarbonate ions, for filling in available absorption space on Fe(III) ox- ides. SEM-EDS methods, performed on retained filters from the filtration of rep- resentative water samples, showed that Pb is mainly transported by fine particulate matter. The chemical elements Mn, Zn, Mo and Sb are predominantly present as dissolved free ions, and correlate strongly with the electrical conductivity of the water samples. 1 Introduction Mineral deposit regional geology and geochemical processes are fundamental con- trols on the surface water quality (Kelley and Taylor 1997). Apart from the very mobile and bioavailable dissolved forms of trace metals, suspended particulate matter and colloids are significant metal carrier phases. Colloids are particles that have at least one dimension in the size range of 1-1000 nm, and due to their small size they have a large specific surface area. These physical properties make col- loids to have a significant impact on the transport of trace metals through sorption N. Lambrakis et al. (Eds.), Advances in the Research of Aquatic Environment, Vol. 2 DOI 10.1007/978-3-642-24076-8, © Springer-Verlag Berlin Heidelberg 2011