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MOBILIZATION AND DISTRIBUTION OF METALS FROM ESTUARINE SEDIMENTS DURING PERIODS OF SIMULATED RESUSPENSION
Citation:
Cantwell, M G. AND R M. Burgess. MOBILIZATION AND DISTRIBUTION OF METALS FROM ESTUARINE SEDIMENTS DURING PERIODS OF SIMULATED RESUSPENSION. Presented at The Society of Environmental Toxicology & Chemistry Annual Meeting, Nashville, TN, November 12-16, 2000.
Description:
For decades, heavy metals have been deposited into marine sediments as a result of anthropogenic activities. Depending on their bioavailability, they may represent a risk to aquatic organisms contributing to the overall degraded conditions present in many estuaries. Over time, marine sediments are subjected to physical processes which resuspends them into the water column, potentially releasing sequestered metals. Natural processes including tides and storms along with anthropogenic induced perturbations such as ship traffic and dredging, are all events which may entrain sediments in the water column. In order to improve predictions of metals behavior following episodic resuspension events, it is essential to understand the factors influencing their distribution. A particle entrainment simulator (PES) is currently being used to resuspend sediments at energy levels representative of estuarine conditions. In this procedure, an intact sediment core is transferred to a test cylinder, overlying water added and the sediment resuspended for a defined period of time. We examined effects of resuspension at two energy levels. Samples are taken at specified intervals and potentially toxic metals (Cd, Cu, Ni, Pb, Zn) are measured in the particulate, colloidal and dissolved phases along with aqueous and particulate organic carbon. Results indicate that the amount of energy imparted to the sediment is an important factor influencing remobilization of metals from the sediments as is duration of resuspension. The sediments' physical and chemical composition also have a direct bearing on the metal mobilization process. Zinc exhibited the greatest response to resuspension, increasing steadily over time in each phase at both energy levels. Copper showed similar increases except for dissolved and colloidal copper which were absent at the lower energy level. Nickel enrichment increased significantly when the level of energy applied was raised, while lead and cadmium had minimal responses. This research will improve our ability to predict the adverse effects of dredging and other perturbations on benthic environments.