Agglomeration, Retention, and Transport Behavior of Manufactured Nanoparticles in Variably-Saturated Porous MediaEPA Grant Number: R833318
Title: Agglomeration, Retention, and Transport Behavior of Manufactured Nanoparticles in Variably-Saturated Porous Media
Investigators: Jin, Yan , Xiao, John
Institution: University of Delaware
EPA Project Officer: Carleton, James N
Project Period: March 1, 2007 through February 28, 2011
Project Amount: $399,035
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: a Joint Research Solicitation-EPA, NSF, NIOSH, NIEHS (2006) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Health Effects , Nanotechnology , Health , Safer Chemicals
The production of significant and increasing quantities of synthetic nanomaterials and our very limited knowledge on their potential environmental and health effects have caused increasing public concerns. The overall objective of the proposed project is to develop an understanding of the fate of nanoparticles released into the subsurface environments. We hypothesize that nanoparticles are likely to be mobile and have the potential to contaminate water resources either as contaminants themselves or by facilitating the transport of other toxic substances. We propose to conduct a comprehensive study to systematically investigate the major processes that control the movement of nanoparticles in the subsurface under environmentally relevant conditions. Our specific objectives are to: (1) determine agglomeration behavior of nanoparticles under different solution chemistry (pH, ionic strength, and presence of dissolved humic material); (2) measure mobility of nanoparticles in model porous media under both saturated and unsaturated flow conditions; and (3) experimentally elucidate the attachment and retention mechanisms of nanoparticles at various interfaces at the pore scale.
We will use TiO2 and Fe nanoparticles as models representing two major categories of nanoparticles that have been used or have the potential to be used in large quantities commercially. Agglomeration of nanoparticles will be evaluated in batch experiments by dynamic light scattering. Transport and potential transformation will be studied with a series of laboratory column experiments using model sand of various surface properties. Sorption and reaction models will be combined with transport models to describe the transport experiments quantitatively. An innovative approach of using confocal microscopy to visualize and analyze particle-particle and particle-interface interactions in micromodels will provide resolution high enough to reveal detailed particle arrangement in bulk solution and at interfaces to elucidate the mechanisms involved in particle attachment and retention at the pore scale.
The proposed project integrates experiments across disciplines (environmental soil physics/hydrology and physics/material science) and scales (column, batch, and pore scale). The results of the proposed study will lead to better understanding of particle-particle and particle-interface interactions at the microscopic level, as well as particle agglomeration, retention, and movement in porous media under various chemical (pH, ionic strength, presence of dissolved humic material) and physical (variable water content) conditions at macroscopic scale. We expect to provide conclusive evidence about the conditions under which transport of NPs is expected and the quantitative magnitude of the process. Such information will contribute to the overall understanding of how nanomaterials interact with the natural environment and provide scientific basis for determining exposure pathways and developing exposure guidelines, which is the first element in risk assessment to quantify potential human health effects.