37. DEVELOMENT OF CALIBRATION STANDARDS FOR USE IN DETERMINATION OF LEAD IN SOILS BY X-RAY FLUORESCENCE

Abstract

In elemental analysis of soils by x-ray fluorescence (XRF), it is necessary to develop a standard curve from soils that have a known content of the metal(s) of interest. For the investigation of heavy metal content of soils such as might occur at a contamination site, calibration of the XRF instrument can be problematic because of the lack of standard soils having a measurable concentration of the metal of interest. Lead, chromium and other metals frequently of interest at environmentally contaminated sites are often below detection limits in uncontaminated soils. In this study, soil samples will be analyzed by flame atomic adsorption to discover their lead content (if any). Then, soil calibration standards for lead in these soils will be developed by spiking the soils with measured amounts of a lead salt. Lead concentration in ppm measured by XRF for the spiked soils will be plotted against known lead concentration to develop a standard curve. The standard curve will then be used with XRF measurements to calculate the lead concentrations for three unrelated soils for which certified lead concentrations are available. XRF calculated and certified lead concentrations will be statistically compared. If the calibration curve developed in this study is shown to give statistically accurate results, it will be used in a related project to determine lead partition coefficients in soil from XRF measurements.