COMPARISON OF LEAD CONCENTRATION IN SURFACE SOIL BY INDUCTED COUPLED PLASMA/OPTICAL EMISSION SPECTROMETRY AND X-RAY FLUORESCENCE

The lead concentration in the surface soil of a French village, where a secondary lead smelter had been operating for a long time, was investigated. The objective was to define the source term of contamination for modelling the blood lead levels of the children living in that village and comparing the predicted values with the observed data. The lead concentration was analysed by Inducted Coupled Plasma/Optical Emission Spectrometry (ICP/OES) and by X-ray fluorescence (XRF). During the first campaign, 48 composite soil samples in the first two centimetre layer were collected and prepared in lab for analysis by ICP/OES. Among these samples, 23 were also analysed by XRF. In a second campaign, field measurements by XRF were performed in 133 spots spread over the village, 24 of these spots being places sampled previously. The analysis of these datasets showed that measurements of soil lead by XRF can provide correct estimates of the soil lead concentrations measured by the reference method. Statistical analyses showed that ICP/OES analysis gives lower values than XRF analysis. For the samples prepared in lab, a regression coefficient equal to 0,9 was calculated between the two types of results. Regarding the common places tested by the lab method (ICP/OES) and the in-situ method (XRF), a linear regression coefficient could also be defined between the two datasets, but the regression coefficient was smaller. The larger discrepancy between the two kinds of values may be explained by the spatial variability of lead concentration at a small scale and the difference of soil volume explored by sampling and the in-situ approach