HR: 0830h
AN: B11C-0708    [PDF]
TI: Review of PIXE Mercury Detection Research at the Louisiana Accelerator Center
AU: Gillan, C
EM: None
AF: Department of Physics University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: * Hollerman, W A
EM: hollerman@louisiana.edu
AF: Department of Physics University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: Lentz, M
EM: None
AF: Department of Physics University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: Lentz, M
EM: None
AF: Louisiana Accelerator Center University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: Glass, G A
EM: glass@louisiana.edu
AF: Louisiana Accelerator Center University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: Greco, R R
EM: none
AF: Louisiana Accelerator Center University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, LA 70504 United States
AU: Liao, C
EM: none
AF: Department of Modern Physics, Lanzhou University, Lanzhou, 73000 China
AU: Doyle, T W
EM: tom_doyle@usgs.gov
AF: National Wetlands Research Center U.S. Geological Survey, 700 Cajundome Boulevard, Lafayette, LA 70506 United States
AU: Lewis, T E
EM: Lewis.Timothy@epamail.epa.gov
AF: National Center for Environmental Assessment Environmental Protection Agency, B-243-01, RTP, NC 27711 United States
AB: Particle Induced X-Ray Emission (PIXE) is non-destructive and allows the simultaneous analysis of elements in solid, liquid, and gas samples. When incident energetic ions strike a target, inner shell electrons of these atoms are ejected as they acquire energy from the incident particle. Outer shell electrons then fill vacancies in the inner shell caused by the ionization. This de-excitation is accompanied by the emission of an Auger electron or x-ray. The ratio of the x-ray production to the probability of ejection of an Auger electron is the fluorescence yield, which ranges from a value of nearly 100% for heavy elements to as low a few percent for light elements. The energy of the emitted x-rays depends on the specific elements present in the target. Since each target element has its own set of characteristic energies in the x-ray spectrum, identifying and determining the concentration of elements is possible. Typically 1-3 MeV ions (usually protons) from a small electrostatic accelerator are used for PIXE analysis. This technique is fast and sensitive; typical limits of detection fall below the ng/cm2 region in the case of surface analysis, or ng/mg (ppm) in the case of concentration measurements. PIXE is two orders of magnitude more sensitive than similar electron-based analysis techniques. Over the last several years, the authors have been using PIXE to detect low concentrations of mercury in tree ring samples. For example, southern magnolia (magnolia grandiflora) tree samples, with known concentrations of mercury, were analyzed using PIXE. Recent published results from these measurements indicate that the average mercury absorption percentage was found to be 85$\pm$ 4%. The distribution of mercury was found to be reasonably homogeneous over the sample surface. However, small variations in mercury concentration are most likely caused by the structure of cellulose in the wood. Mercury in the samples appears to be stable to a total integrated charge of 10 ęC. Three mercury L-shell x-rays are easily observed in the resulting PIXE spectrum. Using PIXE, the mercury detection limit was calculated to be approximately 1 ppm. This poster will provide a history of our mercury detection efforts using PIXE. Our research was completed at the Louisiana Accelerator Center (LAC), which is located on the campus of the University of Louisiana at Lafayette.
UR: http://physics.louisiana.edu/
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting