GEMAS: Geochemical background and mineral potential of emerging tech-critical elements in Europe revealed from low-sampling density geochemical mapping

The demand for ‘high-tech’ element resources (e.g., rare earth elements, lithium, platinum group elements) has increased with their continued consumption in developed countries and the emergence of developing economies. To provide a sound knowledge base for future generations, it is necessary to identify the spatial distribution of critical elements at a broad-scale, and to delineate areas for follow-up surveys. Subsequently, this knowledge can be used to study possible environmental consequences of the increased use of these resources. In this paper, three critical industrial elements (Sb, W, Li) from low-sampling density geochemical mapping at the continental-scale are presented. The geochemical distribution and spatial patterns have been obtained from agricultural soil samples (Ap-horizon, 0–20 cm; N = 2108 samples) collected at a density of 1 site per 2500 km2 and analysed by ICP-MS after a hot aqua regia digestion as part of the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) soil-mapping project in 33 European countries. Most of the geochemical maps show exclusively natural background element concentrations with minor, or without, anthropogenic influence. The maximum extent of the last glaciation is marked as a discrete element concentration break, and a distinct difference occurs in element concentration levels between the soil of northern and southern Europe, most likely an effect of soil genesis, age and weathering. The Sb, W and Li concentrations in soil provide a general overview of element spatial distribution in relation to complexity of the underlying bedrock and element mobility in the surface environment at the continental-scale. The chemical composition of agricultural soil represents largely the primary mineralogy of the source bedrock, the effects of pre- and post-depositional chemical weathering, formation of secondary products, such as clays, and element mobility, either by leaching or mineral sorting. Observed geochemical patterns of Li, W and Sb can be often linked with known mineralisation as recorded in the ProMine Mineral Database, where elements in question occur either as main or secondary resources. Anthropogenic impact has only been identified locally, predominantly in the vicinity of large urban agglomerations. Unexplained high element concentrations may potentially indicate new sources for high-tech elements and should be investigated at a more detailed scale

GEMAS: Spatial distribution of the pH of European agricultural and grazing land soil

During 2008 the GEochemical Mapping of Agricultural Soils (GEMAS) project collected 2108 agricultural (ploughed soil, Ap horizon, 0–20 cm) and 2023 grazing land soil samples (Gr, 0–10 cm) evenly spread over 33 European countries and covering an area of 5.6 million km2. The pH of all samples was determined by one single laboratory applying a 0.01 M CaCl2 extraction, and following a strict quality-control procedure. The resulting pH-value distributions for European Ap and Gr soil are both bimodal. Broad acidic modes, with pH between 4 and 6, and sharp alkaline modes, with pH between 7 and 8 due to the Ca2+ buffer system, are clearly separated. The European median pH is 5.8 for the GEMAS Ap soil samples and 5.5 for the GEMAS Gr soil samples. According to the pH distribution maps, Europe is separated into two main zones: northern Europe with generally lower pH values (Ap: 5.2, Gr: 4.8), dominated by acidic soils occurring in Fennoscandia, and southern Europe with higher pH values (Ap: 6.3, Gr: 5.9), dominated by carbonate rich soils. The separation line coincides with the southern border of the sediments of the last glaciation. The dominant factors controlling pH at the European scale are thus geology (crystalline bedrock) in combination with climate (temperature and precipitation). The GEMAS pH maps mainly reflect the natural site conditions on the European scale, whilst anthropogenic impact is hardly detectable. The GEMAS results provide a unique set of homogenous and spatially representative soil pH data for the continent. The data set defines a dependable continental-scale background, and offers the possibility to calibrate studies on more detailed scales

GEMAS: Geochemical distribution of Mg in agricultural soil of Europe

Agricultural soil (Ap-horizon, 0\u201320 cm) samples were collected from 33 European countries as part of the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) soil-mapping project. The Mg data derived from total concentrations (XRF) and two acid digestion methods, aqua regia (AR) and Mobile Metal Ion (MMI\uae), were used to provide an overview of its spatial distribution in soil at the continental-scale. Magnesium is one of the most abundant elements in the Earth's crust and essential nutrient for plants and animals and its presence in soil is, therefore, important for soil quality evaluation. In this study, the geochemical behaviour of Mg in European agricultural soil was investigated in relation to a variety of soil parent materials, climatic zones, and landscapes. The chemical composition of soil reflects mostly the primary mineralogy of the source bedrock, and the superimposed effects of pre- and post-depositional chemical weathering, controlled by element mobility and formation of secondary phases such as clays. Low Mg concentrations in agricultural soil occur in regions with quartz-rich glacial sediments (Poland, Baltic States, N. Germany), and in soil developed on quartz-rich sandstone parent materials (e.g., central Sweden). High Mg concentrations occur in soil developed over mafic lithologies such as ophiolite belts and in carbonate-rich regions, including karst areas. The maximum extent of the last glaciation is well defined by a Mg concentration break, which is marked by low Mg concentrations in Fennoscandia and north-central Europe, and high Mg concentrations in Mediterranean region. Lithology of parent materials seems to play a key role in the Mg nutritional status of agricultural soil at the European scale. Influence from agricultural practice and use of fertilisers appears to be subordinate. Comparison of the continental-scale spatial distribution of Mg in agricultural soil by using the results from three analytical methods (XRF, AR and MMI\uae) provides complementary information about Mg mobility and its residence time in soil. Thus, allowing evaluation of soil weathering grade and impact of land use exploitation

Mobile Metal Ion® analysis of European agricultural soils: bioavailability, weathering, geogenic patterns and anthropogenic anomalies

Two thousand one hundred and eight agricultural soils (0–20 cm depth) collected at a density of one sample per 2500 km2 under the auspices of the Geochemical Mapping of Agricultural Soils (GEMAS) project over most of the European continent have been analysed using the Mobile Metal Ion (MMI®) partial extraction technique with ICP-MS finish. For a number of elements, notably Ce, Ni, and Ca, coherent geogenic patterns have been observed which relate to underlying lithology. For Fe and Al, coherent patterns are also observed but the effects of weathering are evident, and provide a mechanism to explain the acidity of soils in high rainfall areas. Individual anomalies, many related to anthropogenic activity (mining, metallurgy, agriculture) have been observed for Ag, Au, Cu, Pb, Cd and Zn. Comparison of the results with aqua regia digestion and the equivalent National Geochemistry Survey of Australia (NGSA) provides insights into weathering processes and the concept of bioavailability