Comparative Floe-Bed Sediment Trace Element Partitioning Across Variably Contaminated Aquatic Ecosystems

摘要

Significantly higher concentrations of Ag, As, Cu, Ni and Co are found in floe compared to bed sediments across six variably impacted aquatic ecosystems. In contrast to the observed element and site-specific bed sediment trace element (TE) partitioning patterns, floe TE sequestration is consistently dominated by amorphous oxyhydroxides (FeOOH), which account for 30-79% of floe total TE concentrations, irrespective of system physico-chemistry or elements involved. FeOOH consistently occur in significantly higher concentrations in floe than within bed sediments. Further, comparative concentration (actors indicate significantly higher TE reactivity of floc-FeOOH relative to sediment-FeOOH in all systems investigated, indicating that both the greater abundance and higher reactivity of floc-FeOOH contribute to enhanced floe TE uptake. Results indicate that floc-organics (live cells and exopolymeric substances, EPS) directb/ predict floc-FeOOH concentrations, suggesting an organic structural role in the collection/ templating of FeOOH. This, in turn, facilitates the sequestration of TEs associated with floc-FeOOH formation, imparting the conserved FeOOH "signature" on floe TE geochemistry across sites. Results demonstrate that the organic rich nature of floe exerts an important control over TE geochemistry in aquatic environments, ultimately creating a distinct solid with differing controls over TE behavior than bed sediments in close proximity (<0.5 m).