Impact of Sediment Resuspension Events on the Availability of Heavy Metals in Freshwater Sediments

Abstract

Release of heavy metals during sediment resuspension is an understudied problem that may be cause for environmental concern. Common activities such as shipping and dredging have the ability to resuspend large amounts of contaminated anoxic sediment into the overlying water column. Oxidation of anoxic sediment can alter metal binding, potentially releasing metals into the water column. Understanding fate, bioavailability, and transport of metals is ecologically important, and key to creating more accurate metal speciation and transport models to predict environmental impacts. A Sediment Flux Exposure Chamber (SeFEC) was used to resuspend four types of contaminated sediment to replicate different resuspension scenarios. Dissolved metal concentrations were measured to determine the percent of total metal released. AVS and SEM values were measured to gauge sediment toxicity. Pyrocystis lunula (dinoflagellate) Daphnia magna (zooplankton) and Hyallela azteca (amphipod) were exposed to resuspension conditions to assess biotic endpoints No significant mortality of D. magna and H. azteca was seen. P. lunula exhibited decreased bioluminescence when exposed to bedded sediments, but exhibited mixed responses with resuspended water column samples. . Release of heavy metals to the water column occurred during resuspension. Both increasing and decreasing concentrations were seen through time during consecutive resuspension events.. The findings allow for better determination of the ecological relevance of resuspension events and further the development of metal speciation models by tracing the transport of heavy metals during resuspension events.