Application of Synchrotron X-ray Fluorescence
Spectroscopy and Energy Dispersive X-ray Analysis To
Identify Contaminant Metals on Groundwater Colloids
Daniel I. Kaplan, Douglas B. Hunter, Paul M. Bertsch, Sasa Bajt, and Domy C. Adriano
Division of Biogeochemistry, Savannah River Ecology Laboratory, Aiken, South
It has become increasingly evident that mobile colloids may be a primary vector
for transporting contaminants in subsurface environments (1). A difficulty with
stud ' YM9 and modeling this contaminant transport process has been in defining
clearly whether the contaminants exist in the mobile-aqueous (colloidal) or
mobile-aqueous phase. Traditionally, researchers have assumed that
contaminants were in the colloidal fraction when differences in contaminant
concentrations of ultrafiltrates were measured (2,3). This technique is not entirely
satisfactory because it provides only indirect evidence, is subject to a number of
artifacts, and usually requires high analytical precision at very low contaminant
concentrations (1, 2, 4, 5).
The Synchrotron X-ray fluorescence (SXRF) microprobe at the National
Synchrotron Light Source at Brookhaven National Laboratory, Upton, NY,
may provide a means for distinguishing between contaminants in the aqueous or
solid phase. SXRF is a powerful, nondestructive analytical-technique that ha
detection limits generally between,0.1 and 10 mg kg-1 (6-8). The sensitivity of
SXRF is generally poor for elements with atomic numbers less than 17 (<3 keV)
because of absorption by air and Be windows, low photoionization
crow-wdona, and high selfabsorption (7). The synchrotron-generated X-ray
beam penetrates tens of micrometers through a sample and is highly collimated,
having a typical diameter at the sample of about 10 µm.
SREL Reprint #1853
Kaplan, D.I., D.B. Hunter, P.M. Bertsch, S. Bajt, and D.C. Adriano. 1994.
Application of synchrotron x-ray fluorescence spectroscopy and energy
dispersive x-ray analysis to identify contaminant metals on groundwater colloids.
Environmental Sciences and Technology 28:1186-1189.
To request a reprint