Grantee Research Project Results
2006 Progress Report: Hysteretic Accumulation and Release of Nanomaterials in the Vadose Zone
EPA Grant Number: R832529Title: 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 Period Covered by this Report: September 1, 2005 through August 31, 2006
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: Nanotechnology , Human Health , Safer Chemicals
Objective:
The objective of this work 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 work to be conducted is divided into three primary tasks: (1) batch adsorption/adhesion experiments; (2) saturated deposition/dispersion transport experiments; and (3) dynamic hysteretic unsaturated transport experiments.
Progress Summary:
We have made excellent progress in the first project year on the proposed work. To date, emphasis has been on acquiring equipment and supplies and developing and validating methods for conducting the proposed experiments. In the area of equipment, a dynamic light scattering (DLS)/zeta measurement device was ordered at the start of the grant in September 2005. After an unexpected delay, the device was installed by the company in April 2006. A large-capacity, high-powered wand sonicator also was purchased to facilitate work with large volumes of nanomaterial-containing water for large-scale column experiments. In the area of supplies, we have acquired and begun characterizing 12 different nanomaterials for the work. Additional materials will be purchased as the project progresses, as described in the project proposal.
In the area of research experiments, our emphasis has been in developing techniques for experiments described in Task 3: Dynamic hysteretic unsaturated transport experiments. Work has focused on two aspects of this task: miniature dynamic wetting/drying/infiltration experiments, and measurement of corresponding hysteretic air-water interfacial areas and capillary pressure-saturation (Pc-S) relationships. In addition, preliminary work has been conducted to develop techniques needed for dynamic large-column experiments.
Preliminary results with model systems indicate that the adsorption density of latex nanoparticles at the air-water interface remains approximately constant with saturation at low saturations, and is found to be the same for different porous media. The fact that adsorption density remains constant with saturation at low saturations suggests the effect likely results from interaction with the air-water interface rather than straining by thin liquid films. Experiments with titanium dioxide and tin oxide nanomaterials show significantly greater adsorption to air-water interfaces during drainage in the same porous medium when compared with the latex nanomaterials, despite similar sizes of the three nanomaterials in water. Of the three nanomaterials, tin oxide exhibits the highest adsorption. Preliminary experiments show that while titanium dioxide has a near-constant adsorption density at low saturations, as was observed for the latex nanoparticles, tin oxide (the most strongly adsorbing of the three) appears to have a decreasing adsorption density with decreasing saturation. Reasons for this are not known, but are the focus of ongoing experiments.
Future Activities:
We will continue conducting experiments as described above, following the plan outlined in the original proposal. Ongoing experiments will examine the effects of rate-dependent interface formation, and will study behavior of additional nanomaterials, including those that are expected to adsorb to solid surfaces in addition to the air-water interface. We also will begin to conduct preliminary work with complex sorbents. We hope to begin examining dynamic hysteretic effects in selected systems during the second project year. Ongoing challenges include selection of capillary barriers for specific nanomaterials, development of flow-rate dependent filtration by capillary barriers, and development of detection methods for the range of materials to be studied.
Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Health Risk Assessment, Risk Assessments, Biochemistry, Risk Assessment, bioavailability, nanomaterials, soil pollution, contaminated sediments, structure function relationship, nanochemistry, nanotechnology, fate and transport, vadose zone, carbon fullereneProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.