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Coupling Between Overlying Hydrodynamics, Bioturbation, and Biogeochemical Processes Controls Metal Mobility, Bioavailability, and Toxicity in Sediments

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Technical Report,05 May 2010,29 May 2015

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Northwestern University Evanston United States

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The complex behavior of metals in contaminated sediments often confounds risk assessments and hinders development of effective remediation schemes. We performed laboratory experiments to determine the coupled effects of hydrodynamics, bioturbation, and biogeochemical processes on the transformation, mobility, bioavailability and toxicity of metals in contaminated sediments. Oxidation of surficial sediments liberated metal species that were then mobilized to both pore water and overlying water. Liberation of metals generally increased with hydrodynamic shear on the sediment-water interface, even in some low-permeability sediments. Sediment resuspension transitorily mobilized particulate metals, but did not significantly mobilize dissolved metals or increase contaminant bioavailability or toxicity. Bioturbation and bioirrigation by burrowing worms greatly increased sediment heterogeneity, oxygen delivery into sediments, and efflux of metals to both pore water and overlying water. Bioturbation also destabilized sediments, resulting in greater particle resuspension and metals efflux following flow perturbations. Based on these findings, assessments of metals bioavailability and toxicity in contaminated sediments should include measurements of the effects of flow forcing and sediment resuspension in concert with biological perturbations bioturbation, bioirrigation.

Subject Categories:

  • Hydrology, Limnology and Potamology
  • Toxicology

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