Mary Wornat - US grants

This project involves examination of the behavior of polycyclic aromatic hydrocarbons (PAHs) at the air-water (liquid or frozen) interface to address a number of questions. The activities include measuring the uptake of PAH compounds into fog droplets in the laboratory, and quantification of drop-dependent PAH partitioning into actual fogwater samples. In addition, photochemical reactions of adsorbed PAHs will be studied as functions of temperature, pressure and surface type, and compared with gas-phase loss by photolysis. This information will be useful to understanding the atmospheric fate of PAHs as air masses encounter fog and frozen surfaces (ice and snow).

This project will train an undergraduate student from an underrepresented group, and involve a faculty member from a Historically Black College and University (HBCU) institution. In addition, several other undergraduate students will be involved in the research. The project will be incorporated into two senior research classes in the Chemical Engineering Department. The results of this work will be shared with state and Federal policy makers, in particular those from the Louisiana Department of Environmental Quality, important given the preponderance of fog in southern Louisiana. In addition, collaboration will be fostered between the investigators' institutions (Louisiana State University & Agricultural and Mechanical College, and Colorado State University).

NIRT: Combustion-Generated Nanoparticles--
The Role of Transition Metals in Nanoparticle and Pollutant Formation

CTS-0404314

This project addresses: 1.) The role of combustion-generated metal oxide nanoparticles in the formation/growth of primarily carbonaceous nanoparticles and 2.) The role of metal oxides condensed on growing nanoparticles in the formation of organic pollutants. Ni and Cu have been identified as important metals for initial study. The reactivity of their oxides under a range of conditions is being studied using a variety of experimental techniques. Dendrimeric synthesis techniques is used to create 1-3 nm metal oxide nanoparticles with and without associated carbonaceous layers; sol-gel techniques are used to create thin metal-oxide films on carbon and silica. The reactions of organic chemicals with these nanoparticle surrogates from 200 to 1100 C under oxidative and pyrolytic conditions are studied using a high-temperature flow reactor coupled with GC-MS, EPR, and FTIR analysis. Metal-catalyzed PAH formation is studied using HPLC-UV absorption. The nature of the metal oxides and their chemical binding is characterized using x-ray spectroscopic techniques at the LSU synchrotron facility. Ab initio modeling techniques are used to assess nanoparticle geometries, reaction sites, possible reaction mechanisms, and how they may vary as a function of particle size and metal identity.
It has been estimated that over 650,000 people die prematurely in the US each year due to exposure to airborne fine particles. PM2.5, defined as particles with a mean aerodynamic diameter of less than 2.5 microns, have been shown to initiate cardiopulmonary disease and cancer in exposed populations. It has been realized only recently, however, that submicron, combustion-generated nanoparticles are the likely cause (alone or in combination with other pollutants) for the majority of these deaths and associated illnesses. Although health-effects research programs have been initiated by NIH and EPA, the causative agents remain unknown and progress is hindered by lack of understanding of the complex composition and reactivity of combustion-generated nanoparticles. The impetus of this program is practical, viz. to understand the origin and nature of combustion-generated nanoparticles so that their environmental impact can be minimized. The goal is contribute to the understanding of the chemical factors impacting the health effects of combustion-generated nanoparticles so that their effects can be mitigated or eliminated through combustion control.

This project addresses questions regarding the chemical processing in fog of polynuclear aromatic hydrocarbons (PAHs), some of which are known to be toxic. Specifically: Is there a possibility that fog processing of PAHs could transform them to oxidized compounds (oxy-PAHs) or particles? Might some of the oxy-PAHs be toxic? If so, these compounds might also represent a potential health threat if they are inhaled in a foggy environment. The approach consists of field determination of phase distributions of PAHs and oxy-PAHs throughout smog-fog-smog (SFS) cycles near Fresno, CA and/or at Louisiana State University.

Broader impacts include new perspectives on the cycling of PAHs in atmospheric waters, which are of interest to a broad range of scientists. Graduate students from underrepresented groups are being trained through their participation in the project. Also participating is a faculty member from Prairie View A&M University, a Historically Black College-University institution. Research results are being incorporated into undergraduate courses taught by the principal investigator.