Biogeochemical Control of Heavy Metal Speciation and Bioavailability in Contaminated Marine SedimentsEPA Grant Number: R825220
Title: Biogeochemical Control of Heavy Metal Speciation and Bioavailability in Contaminated Marine Sediments
Investigators: Shine, James P.
Institution: Harvard University
EPA Project Officer: Hahn, Intaek
Project Period: December 2, 1996 through December 1, 2001
Project Amount: $453,630
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
Description:The total concentrations of contaminants in an environmental sample are not indicative of the potential for adverse ecological effects. Contaminant speciation and its effect on bioavailability are critical to understanding ecotoxicology. This information is also crucial for development of policies concerning the use and disposal of toxic material in the environment.
An initiative is currently under way at the national level to understand the factors controlling the toxicity of heavy metals in aquatic sediments. Heavy metals discharged into aquatic ecosystems are likely to be scavenged by particles and removed to the sediments, perhaps leading to a situation where the water is 'clean' yet the underlying sediments have accumulated toxic levels of heavy metals with resultant adverse effects on ecosystem health. The presence of sulfides and particulate organic carbon have been appropriately identified as factors buffering the availability of heavy metals in contaminated sediments. However, even when the ability of these constituents to buffer the toxicity of metals is exhausted, toxicity is not always observed. This implies other binding phases which may also contribute to reduction of metal availability in sediments. These other binding phases may include dissolved and colloidal organic matter in porewaters which can form stable complexes with heavy metals, thus reducing their bioavailability.
The proposed work will examine the role of dissolved and colloidal organic matter on metal speciation and bioavailability in marine sediments. Speciation will be measured at two contaminated locations in New Bedford Harbor, USA, and at a comparison ?clean' location in Buzzards Bay. Observations will be made over multiple seasons to observe temporal and spatial variability these ligands have on metal speciation and bioavailability.
The specific objectives of this proposal are as follows:
1. Develop methods to determine the role of dissolved and colloidal organic ligands on the partitioning of metals between particles and pore water in marine sediments and observe how partitioning varies in space and time.
2. Determine, in conjunction with acid volatile sulfides, how adsorbed (particle bound) and porewater ligands control the availability of heavy metals to transplanted and native benthic organisms.
3. Develop methods to quantify the thermodynamic characteristics of adsorbed and porewater metal binding ligands.
4. Develop the study findings in a framework that assists development of criteria for protection of aquatic ecosystems.