Environmental Behaviors of Solubilized Carbon Nanotubes in Aquatic Systems: Transformation, Sorption, and Toxicity ExposureEPA Grant Number: R834094
Title: Environmental Behaviors of Solubilized Carbon Nanotubes in Aquatic Systems: Transformation, Sorption, and Toxicity Exposure
Investigators: Huang, Qingguo , Black, Marsha C. , Pan, Zhengwei
Institution: University of Georgia
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2008 through August 31, 2011
Project Amount: $383,376
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Fate, Transport, Transformation, and Exposure of Engineered Nanomaterials: A Joint Research Solicitation - EPA, NSF, & DOE (2007) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
The proposed study is aimed to understand the fundamentals that may govern the risks related to aquatic exposure of water-dispersed carbon nanotubes. Several key environmental behaviors relating to aquatic exposure of carbon nanotubes will be investigated, and the studies are designed to examine four specific hypotheses: I) Solubilized carbon nanotubes can be transformed in the environment through certain catalytic oxidative processes, leading to the modification of their physicochemical properties, II) Sorption of solubilized carbon nanotubes on sediments is related to the physicochemical properties of the nanotubes and the sediment materials, resulting in property-dependent differential distribution of the carbon nanotubes in the water and the sediment phases, III) Accumulation and toxicity of solubilized carbon nanotubes by aquatic organisms are dependent on certain physicochemical properties of the nanotubes. Optimal combinations of nanotube size and surface chemistry are predicted to increase bioaccumulation in fish and thus increase their toxicity, and IV) Properties of carbon nanotubes that promote bioaccumulation will also promote transfers of these materials from organism to organism via maternal and trophic transfer mechanisms.
We will employ 14C-labeleing techniques to investigate both single-walled and multiwalled carbon nanotubes that are dispersed in aqueous phases using two different measures (oxidative acid treatment and NOM-assisted dispersing). The hypotheses will be evaluated in five interrelated research tasks that are particularly designed to investigate the different environmental behaviors of solubilized CNTs in relation to their pivotal physicochemical properties, size and surface chemistry. Task 1 involves the preparation and characterization of solubilized 14C-nanotubes. Task 2 focuses on how environmental transformation processes may modify CNT properties, and Task 3 interrogates possible preferential phase distribution as a result of property-dependent sorption. While these tasks investigate how CNT properties may be influenced by environmental factors, Tasks 4 and 5 identify and quantify how variation in CNT properties may impact their bioavailability and inter-organismal transfer.
The proposed study is expected to provide fundamental and systematic information regarding the environmental and exposure behaviors of solubilized carbon nanotubes. This information will enable science-informed assessments of the environmental risks related to aquatic exposure of water-dispersed carbon nanotubes in various scenarios. Such proactive assessments are critically needed by U.S.EPA and the science community to guide a safe development, production, distribution, and disposal of carbon nanomaterials.