The spatial pattern of beryllium and its possible origin using compositional data analysis on a high-density topsoil data set from the Campania Region (Italy)

Abstract

This study demonstrates the spatial distribution of Be and its possible sources by using the high density Campanian topsoil dataset. A combination of univariate and multivariate statistical analysis with multifractal methods were performed on the raw-, and compositionally transformed data set to recognize the spatial patterns of Be and its background values. Specific groups of elements were chosen based on the compositional clr-biplot to implement multiple sequential binary partitions which were used in the calculation of balances. Balances enabled us to reveal the dominance and relation between specific groups of elements. Ratio maps based on balances were also made to better understand the compositional behaviour of Be in a multidimensional space. Index of chemical weathering (CIA) was calculated to explore the advancement of pedogenetic processes which might govern the Be distribution. Enrichment Factor (EF) was used to discover the possible anthropogenic contamination of Be. In addition, different thematic maps (e.g. fault zones, bauxite mineralization spots, hydrothermal springs, pyroclastic and carbonatic rocks distribution) were involved to support and verify our interpretation.Beryllium distribution is influenced by multiple geogenic factors. We proved that Be anomaly in topsoils is not only influenced by the presence of volcanoclastic deposits but the advancement of pedogenetic processes (e.g. chemical weathering, rubification) is equally or even more important. We pointed out that Be anomaly is mainly concentrated in topsoils developed over the oldest pyroclastic deposits in Roccamonfina and over carbonatic massifs where pedogenesis is more advanced. The distribution of pyroclastic deposits in the Campania Region was also demonstrated independently by using different balances (groups of elements). Some high Be anomaly can be interpreted as local peculiarities associated with bauxite mineralization and the presence of fault zones along which hydrothermal deposits and springs are particularly rich in Be. Finally, Be background values reflect geogenic origin and exceed the intervention limit for residential area in the vast majority of the Campania Region, hence decision-makers should take into consideration the local geological conditions when determining intervention limits.