Evaluation of Portable X-ray Flourescence Instrumentation for in situ Measurements of Lead on Contaminated Land

The performance of the Spectrace TN 9000 portable X-ray fluorescence (P-XRF) instrument for in situ sampling and analysis of contaminated soil was evaluated. The method was compared with laboratory analysis of the samples using ICP-AES and XRF as established methods for the assessment of contaminated land. The trueness of the field-based P-XRF results was affected by the soil moisture and the surface roughness of the in situ samples, after the correction of which, no bias was observed between the analytical results of the comparative methods. Relatively large measurement uncertainty (± 55% for Pb) was caused by the small sample mass analysed and the small scale heterogeneity of the sample. This uncertainty was quantified using duplicate measurements and does not impair the delineation of 'hot spots' of contamination as it contributes less than 20% to the total variance. General advantages and limitations of the P-XRF methodology for the investigation of contaminated land were assessed and suggestions are made for the optimisation of the methodology.