How Reliable is X-Ray Fluorescence (XRF) Measurement for Different Metals in Soil Contamination?

Although portable x-ray fluorescence (XRF) technology is widely accepted for environmental use in field screening test regarding the analytical approach, it needs to be evaluated with sufficient data and meet its performance characteristics to be employable for decision making purposes. Usually, for an XRF sample, the most interesting query is: How reliable is the XRF technique in detecting different targeted metals in soil? This study presents pairwise comparisons between the XRF and inductively coupled plasma atomic emission spectrometer (ICP-AES) results for individual elements of Ni, Cu, Zn, Pb, Cd, Cr, Hg, and As. The portable XRF analyzer was used to estimate the concentration levels of eight heavy metal elements, and then pairwise comparisons were made between the XRF and ICP-AES results. Results presented in this paper suggest that the use of XRF testing is highly reliable as a screening technique for the first sample group of metal element (Pb, Zn, Ni, and Cu) concentrations well in excess of the pollution threshold limits (PTLs). The order of reliability of the XRF measurements is Pb > Zn > Ni > Cu, and their relative proximity (RP) ranges from 85%-35%. In contrast, the results of another group of metal elements that include Hg, Cd, Cr, and As show poor correlation. Their RP ranges from 25%-2.3%.