Grantee Research Project Results
2007 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, 2006 through August 31, 2007
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: Human Health , Safer Chemicals , Nanotechnology
Objective:
The objectives of this work are 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: Task 1. Batch adsorption/adhesion experiments; Task 2. Saturated deposition/dispersion transport experiments; and Task 3. Dynamic hysteretic unsaturated transport experiments.
Progress Summary:
We have been making excellent progress in the first two project years on the proposed work. In the first year, after purchasing equipment and refining experimental methods, we systematically began conducting experiments to evaluate project hypotheses. In the second year, we have continued work on experiments examining dynamic transport of nanomaterials in unsaturated porous media, using both custom-designed miniature pressure cells (miniature dynamic wetting/drying/infiltration experiments), and large custom-designed columns (experiments examining the effects of heterogeneity). Other experiments needed to interpret results (e.g., saturated transport experiments) have been conducted in parallel with unsaturated experiments.
Emphasis of the work conducted to date has been on systems where conditions are adjusted so interactions with solid surfaces are minimized, to allow direct assessment of the effects of air-water interface formation on the movement of nanomaterials during dynamic saturation change. Results from miniature dynamic wetting/drying/infiltration experiments have found that faster rates during drainage correspond to lower retention of nanomaterials, and retention is greater at lower saturations. Results of normalizing retained mass by air-water interfacial area suggest that adsorption to air/water interfaces may be the primary mechanism of nanomaterial retention at high saturations (S>0.4), but that straining mechanisms may become increasingly important at lower saturations. Results are qualitatively and quantitatively similar for different kinds of nanomaterials. Large column experiments show retention of nanomaterials in low saturation regions far above the water table. Results indicate that position in the column and the nature of heterogeneity has a significant impact on the retention profile within the column.
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 more nanomaterials, including those that are expected to adsorb to solid surfaces in addition to the air-water interface. We will also begin to conduct preliminary work with complex sorbents, and examine dynamic hysteretic effects in selected systems in the third project year. Ongoing challenges include selection of capillary barriers for specific nanomaterials, flow-rate dependent filtration by capillary barriers, and developing 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, nanochemistry, contaminated sediments, fate and transport, bioavailability, carbon fullerene, nanotechnology, nanomaterials, vadose zone, soil pollution, exposure assessmentProgress 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.