The geochemistry of Niobium and the distribution and relative mobility in agricultural soils of Europe

The Geochemical Mapping of Agricultural and Grazing Land Soil (GEMAS) project provides soil geochemical data for over 50 elements at a density of 1 sample per 2500 km2 across the European continent. Median baseline total concentrations of niobium (Nb) determined by X-ray fluorescence spectrometry in the 95% of Nb in soils can be considered ‘immobile’. All anomalous soil concentrations can be related to geogenic processes. Many of the elevated Nb concentrations are underlain by Hercynian granitic intrusions and alkaline volcanic rocks. High Nb levels also correspond to the occurrence of residual soils over karst areas of southeast Europe and, to some extent, loess deposits of central and Eastern Europe. Lowest Nb concentrations are found in soils developed on most recent glacial sediments of northern Europe. Comparison of the aqua regia extractable concentrations of Nb in both sample types collected within