SREL Reprint #1853

 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, Saša Bajt, and Domy C. Adriano

Division of Biogeochemistry, Savannah River Ecology Laboratory, Aiken, South Carolina 29802

Introduction: It has become increasingly evident that mobile colloids may be a primary vector for transporting contaminants in subsurface environments. A difficulty with studying and modeling this contaminant transport process has been in defining clearly whether the contaminants exist in the mobile-solid (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. 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.
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 has detection limits generally between 0.1 and 10 mg kg-1. 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 cross-sections, and high self-absorption. 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. 

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).