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Amy Dale — 2013-14 Fellow

Project Title: Watershed Modeling for Nanosilver Risk Assessment

Project Description
Silver nanoparticles, or AgNPs, are an effective antibacterial agent. Their microbial toxicity results from their near-atomic (1-100 nm) size, which renders them highly surface reactive. Products containing AgNPs, such as biocidal cosmetics and textiles, are now a major use of nanotechnology in consumer goods. Unfortunately, many of the AgNPs in goods such as socks, paints, and soap will eventually end up in the environment. Initial estimates suggest AgNP emissions to air, soil, and water during manufacturing, use, and disposal may equal as much as 50% of annual production. This is a concern because the toxic effects of AgNPs have been observed in a wide range of organisms, including microorganisms, algae, fungi, vertebrates, invertebrates, and aquatic and terrestrial plants.

Computer simulations are often used to investigate the environmental, health, and safety (EH&S) risks associated with emerging environmental pollutants. During my first two years of Ph.D. study, I modeled the complex sulfide- and oxygen-dependent chemical transformations of AgNPs in sediments. Although sediments are the primary sink for AgNPs released to natural waters, such “single-media” models paint an incomplete picture of AgNP fate and transport. My current work, thus, focuses on the development of a large-scale “multimedia” watershed model in support of public policy decision-making for the safe introduction of nanosilver-containing products to consumer markets.

This model will be used to answer questions such as

  1. How high must environmental releases of AgNPs become before toxicity thresholds or water quality standards are exceeded in the stream or sediments?
  2. What is the relative impact of point sources (wastewater treatment plant effluent) and non-point sources (runoff from agricultural fields on which AgNP-containing WWTP biosolids are used as fertilizer) on the loading of nanosilver to the river network?
  3. How do alternative biosolids application strategies and agricultural “best management practices” for erosion control affect non-point source loadings of nanosilver to the river network? What are the implications of this for risk management?