Comparison of Xrf and Faas Methods in Analysing Cca Contaminated Soils

Soil contamination by hazardous heavy metals from various sources is a great concern nowadays. The need for studying contaminated sites has led to an increasing use of various analytical techniques in the laboratory or in the field, for investigation or control of the restoration operations ofpolluted sites. In this study, results using portable field x-ray fluorescence (XRF)-analyzer X-MET 2000 and flame atomic absorption spectrometry (FAAS) are compared to analyze As, Cu and Cr in soil polluted by chromated copper arsenate (CCA)-wood preservatives. Analyses with XRF were done in situ, in difficult, wet conditions, as well as in the laboratory. For the XRF-analysis, two calibrations were available; an empirical calibration, and recently published fundamental parameter calibrations. Comparative analyses were obtained by extracting As, Cr and Cu with aqua regia and analyzing the samples with flame atomic absorption spectrometry (FAAS). The results indicated that in situ analyses with XRF showed more variation in respect to all three elements than measurements made in the laboratory of dried and sieved (mesh size < 125 μm) samples. XRF's empirical calibration turned out to be more consistent with the FAAS analyses than fundamental parameter calibration, and is therefore recommended. Intrusive laboratory analyses with XRF and FAAS in turn showed good correlation with As and Cu results. FAAS also demonstrated high accuracy and precision as did XRF with As and Cu. On the other hand, Cr results showed more variation, and correlation between the different methods was poorer. To increase the reliability of analysis with both methods, careful drying and sieving the samples is recommended. Therefore we conclude that XRF can be used in field analysis, but laboratory analyses are needed to confirm the results.