A Model of the Transformations of Metal and Metal Oxide Nanoparticles in Freshwater Sediments: Exploring Critical Uncertainties and the Role of Sediments in Nanoparticle Risk Assessment

EPA Grant Number: F13C20565
Title: A Model of the Transformations of Metal and Metal Oxide Nanoparticles in Freshwater Sediments: Exploring Critical Uncertainties and the Role of Sediments in Nanoparticle Risk Assessment
Investigators: Dale, Amy Lauren
Institution: Carnegie Mellon University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2014 through September 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Environmental Risk Assessment

Objective:

This research employs computer simulations to describe the movement and transformation of potentially toxic metal and metal oxide nanoparticles once they are released to the environment during the manufacture, use, or disposal of antibacterial consumer goods produced by the emerging nanotechnology industry. These simulations focus on the strong association of nanoparticles with suspended sediments and soils, which facilitates their accumulation in river and lake beds. The models are used to explore the effect that natural variability in environmental conditions—such as stream flow, temperature, oxygen availability and pH—has on the toxicity, bioavailability and persistence of metal and metal oxide nanoparticles and their reaction by-products in sediment beds and overlying surface waters.

Approach:

This research focuses on the development of two mathematical models to investigate the fate of three highly reactive nanoparticles—zinc oxide, copper oxide and silver—in terrestrial and aquatic environments. The first model, which is highly detailed and small in scale, focuses on the chemical transformations that nanoparticles and their reaction by-products (metal ions) undergo in the river beds and lake beds where they are expected to accumulate once released to the environment. The second model, which links an adaptation of the Chesapeake Bay Program Phase 5 Watershed Model to the U.S. EPA’s water quality model WASP7, is a watershedscale simulation that is informed by the sediment model and is designed to describe the fate of nanoparticles released to the James River basin in Virginia. Features of the model include geospatial information on the location and discharges of all permitted sewage treatment plants in the watershed; hourly rainfall patterns over a 20-year period; daily estimates of stream flow; data on agricultural and urban land use in the watershed; and a detailed description of sediment transport on the land surface and in the river network.

Expected Results:

This work will predict the ultimate location, concentration and form of silver, zinc oxide and copper oxide nanoparticles released to surface waters and sediments. Predictions will indicate whether the nanoparticles will be present in toxic forms at high enough concentrations to be of concern. Overall nanoparticle mobility in the environment is expected to be low, and most environmental toxicity will likely be observed in the sediments or at the sediment-water interface. Nanoparticle risk will depend heavily on such site-specific factors as pH, oxygen availability and sulfide availability. Nanoparticle concentrations in the stream will depend heavily on stream flow due to the impact of flow on sediment transport. Uncertainty analysis will be used to determine which uncertainties in model inputs have the greatest effect on model predictions, which will help prioritize future research.

Potential to Further Environmental/Human Health Protection

This research aims to advance the emerging field of nanoparticle fate and transport modeling by adapting modeling frameworks historically developed for “conventional” or non-nano pollutants, such as metal salts and pesticides. These models will be used to shed light on the environmental transformation, toxicity and bioavailability of reactive metal and metal oxide nanoparticles under a wide range of environmental conditions. Results will be used to inform public policy and risk management decision making for this emerging class of potential environmental pollutants.

Supplemental Keywords:

metal contamination, nanomaterials, risk assessment

Progress and Final Reports:

  • 2015
  • Final