This project has two parallel research objectives to transfer and expand the expertise of the U.S.-based researcher, Dr. Maria Chrysochoou to the host institution, the National Technical University of Athens (NTUA). The first objective addresses a frequent environmental problem, the mobility of hexavalent chromium (Cr(VI)) in polluted groundwater. Surface complexation modeling relies in recent years on spectroscopic and theoretical investigations of the binding mechanisms of metal contaminants on mineral surfaces; however, very limited studies have been conducted for Cr(VI). The researcher will utilize Fourier Transform Infrared spectroscopy, Extended X-ray Absorption Fine Structure spectroscopy and Density Functional Theory calculations in combination with traditional sorption isotherms to study the complexation mechanisms of Cr(VI) on important sorptive surfaces (ferrihydrite, hematite, corundum and γ-alumina) under various conditions (pH, surface loading, competitive anions). The generated data will be used in future research to construct data-driven surface complexation models for Cr(VI). The second objective will be pursued as an add-on to a LIFE project coordinated by NTUA (Chromium in Asopos River System: Remediation Technologies and Measures) to guide the risk assessment and remediation efforts for this Cr(VI)-polluted area in Greece. Micro-X-ray Fluorescence, Absorption Near Edge Structure (μXANES) and Diffraction along with bulk XANES will be used to determine the binding mechanisms of Cr(VI) in the aquifer and refine the transport model and treatment design. The proposed work will build the expertise of the two participating labs (Sanitary Engineering Laboratory and Laboratory of Metallurgy) in spectroscopic techniques, adding an important element to their environmental research portfolio. Additionally, Dr. Chrysochoou will bring her diverse collaborations from the U.S. to the European Research Area, where she intends to continue her academic career.