Valutazione dei valori di fondo naturale di metalli mediante analisi XRF in aree minerarie dismesse in valle Anzasca = Assessment of natural background values of metals by XRF analysis in areas disused mines in the Anzasca valley

Within the Mining District Est of Monte Rosa, this study aims at a threefold objective : •??to implement the knowledge of the background values in the soils of other heavy metals (Arsenic, Mercury, Chromium, Zinc, Rubidium, Strontium, Zirconium, Lead, Manganese and Barium), using more rapid characterization surveys and methodologies (XRF) and statistical analysis; •??provide the community with useful references on the new limits of remediation of specific regulated metals, in the local natural context as required by art. 240 point b of D.Lgs. 152/06; •??to compare the background value of arsenic in the study areas with two different sampling and analysis methodologies. The campaign of measurements with more than 200 points of investigation using surveys and methodologies more expeditive characterization (Xrf) and analysis, compared with the values acquired with classical sampling and laboratory analysis methods, gave identical results on the background values for the Arsenic parameter. XRF is reliable and repeatable for the investigation of the natural background value of arsenic and with this evidence the knowledge of the background values in the soils of other heavy metals (Chromium, Zinc, Rubidium, Strontium, Zirconium, Lead, Manganese and Barium) has been implemented using the same technique and statistical analysis. For lead the background value can be assimilated to the CSC even if it is just above the threshold of concentration of public green. For zinc the background value is 3 times the CSC for residential and public green areas and at a half time higher than the concentrations of the admissibility of sewage sludge impelled in agriculture in spreading on the soil. The Fund value is however lower than the CSC for industrial Therefore, in a site potentially contaminated within the areas investigated, for zinc, the exceeding of the contamination threshold, will be taken equal to the identified background value of 453.9 mg/kg.areas. Similar evaluations may also be carried out for Zr, Sr, Rb, Mn, Ba, although for these elements, in the D.Lgs. mentioned no threshold values of contamination have been identified. It may also be useful, in certain cases, with regard to the spreading of sludge in agricolture to take the account of the high levels of zinc naturally occurring in soils.