Contaminated soils present a major global health problem especially in urban areas with dense population. The common contaminants of soil are heavy metals. Research investigating the risk assessment procedures adopted in different EU member states, suggests that there needs to be greater standardization in the methods of assessing risks from contaminated soils. For risk-assessment studies and follow-up remediation projects is necessary to perform numerous analyses to determine the concentration of metal contaminants. To minimize the need for laboratory analysis of soil samples, the XRF - technology can be used for screening the metal contamination in soil, with significant advantages. This method provided significant accuracy and well documented to support field decision making with reduced overall costs. The new generation of portable XRF instruments is equipped with miniatures X-ray tubes in order to reduce the regulatory demands encountered with radioactive isotopes.The goal of this experiment was to complete the data obtained in the preliminary tests, by observing the correlation between XRF results and laboratory analysis data in heavy metal determination. Soil samples were collected from an old metallurgical industrial area, situated in the vicinity of Bucharest, Romania. The X-ray tube based sources offer a faster analytical time because the X-ray flux can be higher than most isotope based sources. They can also be used over a wider range of excitation energies, eliminating the need for multiple isotope sources to produce X-ray over the entire excitation spectrum. The collected samples were XRF measured, then dried in air, XRF measured, sieved through the 2 mm sieve to remove non-soil particles and XRF measured again. The samples were homogenized and passed through the 200 microns sieve and XRF measured. After XRF determination, these fine samples were laboratory analized (XRF analysis being nondestructive). The XRF results are presented comparatively with laboratory analysis data. From these results is evident that the soil particle size have no important influence upon the XRF data, an important factor appears to be the metal concentration in soil. The results confirm the influence of metal concentration in soil upon the XRF data, smaller is metal concentration in soil sample, higher are the difference between XRF and laboratory analysis results. In all samples laboratory results are many times smaller than XRF data, in chromium and cobalt determination. Best correlation was obtained in lead and manganese determination.

heavy metals, soil, portable X-ray fluorescence instrument

Presentation: oral