Nanoparticle Stability in Natural Waters and its Implication for Metal Toxicity to Water Column and Benthic Organisms

Project Information

Principal Investigator	James Ranville
Institution
Project URL	View
Relevance to Implications	High
Class of Nanomaterial	Engineered Nanomaterials
Impact Sector	Environment
Broad Research Categories	Hazard Generation, Dispersion, Transformation etc.
NNI identifier

Funding Information

Country	USA
Anticipated Total Funding	n/a
Annual Funding	n/a
Funding Source	EPA
Funding Mechanism	Extramural
Funding Sector	Government
Start Year	2007
Anticipated End Year	2010

Abstract/Summary

Objective:

The overall hypothesis is that metal-containing manufactured nanomaterials pose an exposure and toxicological risk to aquatic organisms. The toxic ‘species’ may be the nanoparticle or dissolved metal ions liberated following (partial) dissolution. We hypothesize that exposure in the water column will be a function of dissolution rate and aggregation rate of the nanoparticle. Water chemistry is known to strongly influence dissolved metal uptake by organisms, as described by the biotic ligand model. For the (nano)particulate phase, water chemistry plays an additional role in that it greatly influences particle stability and fate (e.g. sedimentation) in surface waters. We further hypothesize that exposure to benthic organisms may occur, after aggregation and settling of nanoparticles, through ingestion of sediment. We propose to address three objectives in this research: 1) determine the stability (against aggregation and dissolution) of nanoparticles as a function of water composition; 2) determine the uptake, distribution, and elimination of metals from dissolved and nanoparticle phases within Daphnia magna organisms under variable water compositions; and 3) determine the uptake, distribution, and elimination of metals from dissolved and aggregated nanoparticle phases within Hyalella azteca organisms under variable water compositions.

Approach:

We propose to study the uncapped quantum dot (QD) CdSe and the capped CdSe/ZnS QD. We will also study ZnS and ZnO nanoparticles, which could represent partial dissolution products. We will use electron microscopy, fluorescence microscopy, field flow fractionation, enriched stable isotope tracers, high resolution ICP-MS, and synchrotron Xray techniques to fully characterize the nanoparticles in the water column and in the sediment in carefully-controlled laboratory microcosms. We will couple this characterization to bioavailability studies employing commonly used organisms (i.e., Daphnia magna and Hyalella azteca) so that our results with nanoparticles will be directly comparable to toxicity data for the relevant dissolved metals.

Expected Results:

This study will provide important new information on the fate of nanoparticles in surface water. We will provide some needed basic information on the stability of nanoparticles in waters of variable composition. Stability and toxicological results will demonstrate the potential for adverse effects to aquatic ecosystems, when these systems are exposed to QDs through increased use and environmental release.