GEMAS: Cadmium distribution and its sources in agricultural and grazing land soil of Europe â\u80\u94 Original data versus clr-transformed data

Over 4000 agricultural and grazing land soil samples were collected for the â\u80\u9cGeochemical Mapping of Agricultural and Grazing Land Soil of Europeâ\u80\u9d (GEMAS) project carried out by the EuroGeoSurveys Geochemistry Expert Group. The samples were collected in 33 European countries, covering 5.6 million km2at a density of 1 sample site per 2500 km2. All samples were analysed by ICP-MS following an aqua regia extraction. The European median Cd concentration is 0.182 mg/kg in agricultural soil and 0.197 mg/kg in grazing land soil (including eastern Ukraine). The Cd map demonstrates the existence of two different geochemical background regimes in northern and southern Europe, separated by the southern limit of the Quaternary glaciation. Cadmium shows two times higher background concentrations in the older and more weathered southern European soil than in northern European soil. The spatial distribution patterns of Cd in the collected soil samples are mainly governed by geology (parent material and mineralisation), as well as weathering, soil formation and climate since the last glaciation period. Locally, in several areas, the natural anomaly pattern is overprinted by anthropogenic emissions from former mining, ore processing and related metal industries. Some Cd anomalies can be attributed to urbanisation and the use of fertilisers. A comparison of the raw data Cd concentration map with its clr-transformed counterpart and selected single element ratio maps demonstrates that substantial additional information about sources and processes governing the distribution of Cd in agricultural soil at the European scale can be obtained. Results of a PCA, carried out following the classical approach (standardised) versus a PCA based on the statistically acceptable approach, using clr-transformed data, are quite comparable

GEMAS: Establishing geochemical background and threshold for 53 chemical elements in European agricultural soil

The GEMAS (geochemical mapping of agricultural soil) project collected 2108 Ap horizon soil samples from regularly ploughed fields in 33 European countries, covering 5.6 million km2. The <2 mm fraction of these samples was analysed for 53 elements by ICP-MS and ICP-AES, following a HNO3/HCl/H2O (modified aqua regia) digestion. Results are used here to establish the geochemical background variation and threshold values, derived statistically from the data set, in order to identify unusually high element concentrations for these elements in the Ap samples. Potentially toxic elements (PTEs), namely Ag, B, As, Ba, Bi, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, U, V and Zn, and emerging ‘high-tech’ critical elements (HTCEs), i.e., lanthanides (e.g., Ce, La), Be, Ga, Ge, In, Li and Tl, are of particular interest. For the latter, neither geochemical background nor threshold at the European scale has been established before. Large differences in the spatial distribution of many elements are observed between northern and southern Europe. It was thus necessary to establish three different sets of geochemical threshold values, one for the whole of Europe, a second for northern and a third for southern Europe. These values were then compared to existing soil guideline values for (eco)toxicological effects of these elements, as defined by various European authorities. The regional sample distribution with concentrations above the threshold values is studied, based on the GEMAS data set, following different methods of determination. Occasionally local contamination sources (e.g., cities, metal smelters, power plants, agriculture) can be identified. No indications could be detected at the continental scale for a significant impact of diffuse contamination on the regional distribution of element concentrations in the European agricultural soil samples. At this European scale, the variation in the natural background concentration of all investigated elements in the agricultural soil samples is much larger than any anthropogenic impact