Beryllium natural background concentration and mobility: a reappraisal examining the case of high Be-bearing pyroclastic rocks

Beryllium is widely distributed in soils at low levels, but it can also occur naturally in higher concentrations in a variety of materials exploited for many industrial applications. Beryllium is also one of the most toxic natural elements and is known to be a human carcinogen. A concise account of the literature data on baseline concentrations of Be in soils illustrates the possibility of worldwide presence of areas with a high natural background concentration of Be (up to 300 mg/kg), the crustal abundance of which is generally estimated to be in the range 2-6 mg/kg. Nethertheless the number of available data is rather limited in comparison with those about other toxic elements such as Pb, Cd, Cr…This could have probabibly caused the choice of low values of concentration level as the reference ones for the definition of soil as contaminated: these values are not always realistic and applicable to large areas.As a case study we report and analyse a diffuse, unusually high (up to 80 mg/kg, average approximately 20 mg/kg), natural occurrence of beryllium in loose and poorly consolidated pyroclastic layers related to the Pleistocene activity of the Vico volcano. Additionally, the analysis of Be leachability has been carried out, providing evidence of a not negligible mobility in contrast with the scarce data presented in the literature that usually indicate beryllium as an element with low mobility in slighty acidic and oxidising surface environmental conditions. This research is proposed as a starting point for a possible possible reappraisal of beryllium geochemical behaviour and background levels, providing more realistic and flexible reference values for risk assessment and land management.