"A portable X-ray fluorescence method is described for the measurement of lead and arsenic in soils based on calibration with standard reference materials. Both elements exhibited good linear calibration curves. The method was used to analyze dried and ground soil samples obtained from the metropolitan New York City area. Results were compared to measurements obtained by graphite furnace atomic absorption spectrometry with microwave assisted acid leaching. No significant difference was found for lead measurements between the two methods however, arsenic values were significantly different with XRF exhibiting higher values. It is hypothesized that incomplete leaching and spectral interference are the predominant causes of this discrepancy. The XRF method provides a simple, quick, and nondestructive method for the determination of total lead and arsenic content in soils.
Fusing soil standard reference materials as calibration standards is an acceptable method for the determination of lead in dried and ground soils. XRF and acid leachable GFAA methods provide statistically similar results for lead but not for arsenic which we believe to be due to arsenic at relatively low concentrations tending to be strongly bound to the soil and not easily acid leachable. An alternative explanation is that it is an effect of uncompensated spectral interference although we believe this is more likely to affect precision than accuracy. Poor precision was observed for XRF measurements particularly for arsenic. Using soil standard reference materials offers a matrix matched calibration method and avoids needing to perform significant sample preparation or reliance on algorithms provided by the instrument manufacturer.
Last date updated on July, 2014