Methods and Measurements of Nanoparticle Distribution in the Natural Environment

Summary

Given the substantial differences between nanoparticles (NPs) and typical organic and inorganic environmental contaminants, new methods and analytical techniques are needed to accurately measure concentrations of NPs in environmental matrices. These measurements are important because the environmental behavior of NPs will influence the extent to which NPs can transport to groundwater at which point they could be ingested by humans utilizing wells for their drinking water, and it will also influence which ecological receptors (e.g., fish or sediment-dwelling organisms) are exposed to NPs and at what concentrations.

Description

Intended Impact

Understanding the potential environmental fate of NPs has direct implications to the US economy, as potential environmental and human health impacts of NPs is one of the main factors slowing the commercialization of this technology. Reducing the uncertainty regarding the environmental fate and risks of NPs will facilitate sustainable commercialization of products utilizing NPs. The results from this project are expected to also help other government agencies such as EPA and FDA with a robust and scientifically grounded risk assessment of NPs.

Objective

The primary objectives of this project are to develop transferable methodologies that can be used to accurately measure the environmental fate (i.e., sorption, settling, biodegradation) of various NPs, and acquire a mechanistic understanding of critical NP properties that determine their fate.

Goals

1. Develop methods to assess sorption and desorption of carbon nanotubes and fullerenes with different types of soil particles (i.e., peat and shale) and different soils and sediments.
2. Acquire a mechanistic understanding of which NP and soil properties influence the sorption behaviors of carbon nanotubes and fullerenes.
3. Determine which water characteristics (natural organic matter concentration, hardness, etc.) predominantly influence the settling of dispersed fullerenes in natural waters.
4. Develop methods to measure the NPs release from landfills
5. Develop methods to assess the biodegradation of carbon nanotubes and fullerenes.
6. Develop methods to assess transport of carbon nanotubes in natural soils

Research Activities and Technical Approach

Carbon-14 labeled carbon nanotubes (multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs)) and fullerenes will be used to make novel measurements of these carbon NPs in various environmental matrices such as soils and sediments. Sorption of dispersed MWCNTs, SWCNTs and fullerenes will be made using completely mixed batch reactors with concentrations of soils, sediments, or a specific type of soil particle. The influence of dissolved organic matter from the soil and sediment materials will be assessed by testing the phase distribution of carbon nanotubes and fullerenes in solutions with only water, water with dissolved organic matter, and water with dissolved organic matter and solid soil and sediment particles. The pH and ionic strength will also be varied to determine the extent to which water quality characteristics influence the sorption behaviors. Fullerenes will be suspended in three different well-characterized natural lake waters and a synthetic lake water and their settling behavior will be tested for one year. Transport of carbon NPs out of landfills will be assessed using diffusion experiments across geomembranes that are typically present in the linings of landfills. Transport of carbon nanotubes in soils will also be modeled using carbon-14 nanotubes and natural soils. The biodegradation of carbon nanotubes and fullerenes will be assessed by measuring released carbon-14 dioxide after C-14 labeled carbon nanotubes and fullerenes are exposed to various types of bacteria and fungi.

Major Accomplishments

• Dissolved organic matter released from soils was found to have a major impact on sorption of MWCNTs to peat unlike for typical organic chemical pollutants.
• Biodegradation of MWCNTs was observed in the presence of some bacteria species