Fig. 6. In situ X-ray absorption near edge structure (XANES) spectra and their first derivative of the Cu-contaminated soil treated by electrokinetic remediation (EKR) for (a) 0, (b) 60, (c) 120, and (d) 180 min. Solid lines and circles represent experimental data and the least-square fits, respectively. Dotted lines denote fractional contributions of the five main components (Cu–humic substances [HS], CuCO_3, CuO, Cu₂O, and aqueous Cu²⁺) making up the fitted spectra.