Title page for ETD etd-06302009-221900


Type of Document Dissertation
Author Ashley, Nicholas A.
Author's Email Address nickashley@live.com
URN etd-06302009-221900
Title Particle-Chemical Interactions and Environmental Chemodynamics of Fine and Ultrafine Particles in a Natural Disaster Scenario
Degree Doctor of Philosophy (Ph.D.)
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Kalliat T. Valsaraj Committee Co-Chair
Louis J. Thibodeaux Committee Co-Chair
Michael G. Benton Committee Member
Ralph W. Pike Committee Member
Allan G. Pulsipher Dean's Representative
Keywords
  • mathematical modeling
  • nanoparticles
  • sediment
  • Hurricane Katrina
Date of Defense 2009-06-12
Availability unrestricted
Abstract
The interactions of fine and ultrafine particles with chemicals play a dominant role in determining the mobility and availability of pollutants in the environment. Fine particles in sediments can sequester chemicals from the water column, and release volatile and semi-volatile organic compounds to the gas phase upon exposure to air. Ultrafine particles which are photoreactive can degrade these vapor-phase contaminants, and may transform the molecules into species which are more toxic or hazardous than the parent. As the widespread, commercial use of ultrafine particles becomes more common, understanding the chemodynamics of these particles and their interactions with chemicals in the environment becomes paramount.

Flooding in the city of New Orleans caused by Hurricane Katrina introduced numerous sediment-laden pollutants to the city. Of particular interest are contaminated sediments which were deposited inside homes and buildings. The fine particles in these sediments which sequester metal and organic pollutants serve as a direct exposure source to persons working inside the structures, both in the sediment as well as by releasing volatile and semi-volatile organic chemicals to the vapor phase. Mathematical models are needed which can provide a quantitative description of the processes which mobilize and transport contaminants in enclosed buildings, in order to understand the short- and long-term chemodynamic behavior of sediment pollutants inside flood-damaged structures. Two chemodynamic models are developed to describe this behavior, a thermodynamic-based equilibrium model and an unsteady-state fate and transport model. Both models can be used to ascertain the classes and quantities of pollutants to which persons working inside the flooded homes may be exposed.

Volatile and semi-volatile organic pollutants in the vapor phase can encounter photoreactive ultrafine titanium dioxide particles, embedded into paint and sunscreen-coated surfaces or as aerosolized particulates. Kinetic data for the degradation rates of organic compounds on these paint and sunscreen surfaces is severely lacking, especially for the semi-volatiles. Surface reaction experiments are carried out in order to collect some of this much-needed data. Observed reaction rates are found to vary as functions of both material thickness, due to mass transfer resistances, as well as ambient relative humidity, through the production of surface hydroxyl radicals.

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