Riparian floodplains are frequently affected by pronounced redox fluctuations, with important consequences for trace metal speciation and release. To investigate the dynamics of trace metal release, we conducted soil microcosm experiments at 5, 14, and 23 �C using contaminated soil from the Mulde River in Germany. Pore water sampled during 33 days of flooding was analyzed for dissolved (<0.025 �m) and colloidal metal concentrations, SO42-, DOC, pH, and Eh, respectively. Colloids were characterized by transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) at the Cu-K and Hg-LIII edges, respectively. TEM and XAS revealed rapid formation of metallic Cu(0) nanoparticles upon flooding. Hg(0) was also formed and incorporated into the crystal lattice of metallic Cu(0). With onset of sulfate reduction, however, Cu(0) particles appeared to be transformed to CuxS. TEM results suggested that Hg was then incorporated into Cu-rich metal sulfides rather than forming a separate HgS phase.

Temperature-dependent formation of colloidal Cu(0) and Cu<sub>x</sub>S induced by soil flooding and its influence on Hg dynamics

243rd National Meeting (2012)

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Temperature-dependent formation of colloidal Cu(0) and CuxS induced by soil flooding and its influence on Hg dynamics

Temperature-dependent formation of colloidal Cu(0) and Cu_xS induced by soil flooding and its influence on Hg dynamics