Hysteretic Accumulation and Release of Nanomaterials in the Vadose ZoneEPA Grant Number: R832529
Title: Hysteretic Accumulation and Release of Nanomaterials in the Vadose Zone
Investigators: Kibbey, Tohren C.G. , Sabatini, David A.
Institution: University of Oklahoma
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through August 31, 2009
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: A Joint Research Solicitation - EPA, NSF, NIOSH (2005) RFA Text | Recipients Lists
Research Category: Health , Safer Chemicals , Nanotechnology
Manufactured nanomaterials are increasingly being considered for use in a wide range of applications, and their use is projected to expand substantially during the next ten years as costs decrease and new applications are discovered. At present, little is known about the fate, transport, or transformation of nanomaterials in the environment, or their inherent risks to human or environmental health. The objective of this project is to study the vadose zone accumulation and release of a wide range of manufactured nanomaterials, with emphasis on hysteretic interactions with air/water interfaces and specific mineral surfaces. Nanomaterials can enter the vadose zone through infiltration of atmospheric dispersions, or from groundwater contaminated by landfill leachate or other sources. Depending on the nature of the materials and interactions with critical interfaces, the vadose zone may either provide a sink for nanomaterials, preventing their spread throughout the environment, or a long-term contaminant source.
The proposed research will be conducted through three primary tasks: Task 1. Batch adsorption/adhesion experiments, designed to assess adsorption/adhesion affinities with critical liquid/solid and liquid/air interfaces; Task 2. Saturated deposition/dispersion transport experiments, designed to evaluate dynamic interactions between nanomaterials and mineral surfaces; and Task 3. Dynamic hysteretic unsaturated transport experiments, designed to provide detailed information about the effects of wetting/drying history, infiltration, and unsaturated soil behavior on the accumulation and release of nanomaterials. As described in the Research Plan, these tasks use a range of experimental systems to study specific mechanisms influencing the dynamic accumulation and release of manufactured nanomaterials in the vadose zone, and make extensive use of inline detectors to simultaneously track concentration, and particle size and zeta potential distributions. A novel technique for measurement of air/water interfacial area throughout hysteretic wetting/drying cycles will provide fundamental experimental information about the role of wetting state history and air/water interfacial areas in the accumulation and release of nanomaterials. As described in section E.2.1.a., nanomaterials selected for this work cover a wide range of structures, compositions, and physical and chemical properties, in addition to different potential applications. The solid media selected for this work will include fully-characterized whole soils and aquifer materials, as well as critical mineral subsets of the whole materials. An unsaturated flow and transport modeling effort conducted as a part of Task 3 will integrate the results of experimental tasks.
The proposed work will provide significant benefits to society in terms of improved a priori assessment of manufactured nanomaterial mobility in the environment and associated risk. Outcomes of the work will provide indications about the classes of nanomaterials most likely to accumulate in the vadose zone, the roles of mineral surfaces, air/water interfacial areas, and wetting/drying history on accumulation. This work will provide essential new information necessary to assess the mobility of manufactured nanomaterials in the environment and the role of vadose zone interactions in decreasing or increasing ultimate risk to human or environmental health.