Authors: Rheo B. Lamorena-Lim, Ericho M. Fuentes and Elmer S. Austria Jr.
The potential speciation of the heavy metals As, Cd, Cr, Cu, Hg, Pb and Zn in a main creek of a river-based mining site were determined via solution speciation with equilibrium phase simulation using the geochemical software PHREEQC. Five sampling sites were used, one located upstream, three locations were selected midstream, which were used to monitor chemical mixing patterns in stream junctions, and one location downstream in order to monitor deposition behavior of metals. Input data for the software included pH, dissolved oxygen, aqueous and sediment concentrations of the said metals, as well as the amounts of minerals present as determined by X-ray diffraction and petrographic analysis. Simulations show the prevalence of As(V), Cr(VI), Cu(II) and Hg(II) species among all other oxidation states of the given elements. Leaching trends and mineral formation trends for Cr and Zn trends were also observed in the sediment and XRD analysis data.
Keywords: heavy metals; speciation; PHREEQC