X-RAY ANALYSES OF ELEMENTAL CONCENTRATIONS IN FEATHERS: COMPARISON OF XRF AND PIXE
Abstract
The X-ray analysis techniques of X-ray Fluorescence (XRF) and Particle-Induced X-ray Emission (PIXE) were tested for their sensitivity, precision, and accuracy in conducting elemental analyses on feathers. XRF could detect 21 elements directly in the sample matrix with minimum detectable limits of 0.5 to 1 μg/g for most elements. Due to the feather's thickness, a correction factor was applied to account for X-rays absorbed within the sample matrix. To confirm the results obtained by XRF, atomic absorption spectroscopy was conducted for mercury on four samples analyzed by XRF and the results were consistent between the two analytical techniques. The feathers, which ranged from 3 to 7 mg/cm2 in areal density, proved too thick for straightforward analysis by PIXE. While corrections could have been applied, the feather's structure makes the task difficult and the beam attenuation correction would compound the already large X-ray absorption correction factor.
The XRF system was then tested for its effectiveness in two field studies. The first project used XRF to determine geographic differences between two populations of brown pelicans where nine of the fourteen elements routinely detected varied between the populations. The second project used XRF to trace mercury contamination in birds at Clear Lake, CA. The feathers showed elevated mercury concentrations while other potential contaminants were low.
