REVISITING THE LINKAGES BETWEEN METALS BIOAVAILABILITY AND SEDIMENT EXTRACTIONS: LESSONS FROM THE DETROIT RIVER

Introduction: Significant efforts have been made to develop a database and a regulatory framework that can accurately describe the mobility, and environmental health risks of metals in aquatic systems. However, the binding capacity of many of the sediments, as well as acute toxicity of these metals in complex multi-component systems has yet to be quantified. Without a molecular scale understanding of the factors regulating contaminant dynamics in these systems, government agencies will continue to rely on the total concentrations of various contaminants in soils, sediments, surface and groundwaters to provide a regulatory framework to establish risk. It is clear that the toxicity of metals (or bioavailability) in these environments is more closely tied to chemical and physical state or speciation than to bulk concentration within the system (e.g. Campbell, 1995). There is an urgent need to develop new techniques to study and quantify the bioavailability of contaminants in systems such as the Detroit River to help guide and evaluate remediation at metal laded sites. Our rapid metal extraction procedure may be a valuable tool in the evaluation of metals’ bioavailability in several areas of the Detroit River.

Methods: Cores were extracted from 5 sites in 2001, and immediately upon return to the laboratory sectioned (cm) and frozen in polypropylene containers. Core section mineralogy was analyzed by XRD, carbon content by loss on ignition, and total metals content (aqua regia). Metals’ bioavailability was investigated for each core via cold acetic acid extraction procedure. Extracted solutions were analyzed for metal content via ICP-OES and ICP-MS.

Results: Our initial results indicate our extraction procedure provides an excellent snapshot of the mobility and availability of trace and heavy metals in the Detroit river sediments without the complexity of introducing several reagents into an extraction protocol. The protocol also limited interferences with ICP-MS based techniques. The sediment bioavailable metals content varied between the core sites, ranging from 40-90%.