GEMAS: adaptation of weathering indices for European agricultural soil derived from carbonate parent materials

Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur on a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, and which is useful for evaluating chemical weathering trends (e.g. the Chemical Index of Alteration (CIA) or the Mafic Index of Alteration (MIA)). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source-rock types at the continental scale, and allows a more robust interpretation of soil parent-material weathering grade and its impact on the current chemical composition of soil. An increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na, and precipitation of Fe-oxides and hydroxides. The relation between soil weathering status and its spatial distribution in Europe provides important information about the role played by climate and terrain. The geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination

Mercury in European agricultural and grazing land soils

Agricultural (Ap, Ap-horizon, 0–20 cm) and grazing land soil samples (Gr, 0–10 cm) were collected from a large part of Europe (33 countries, 5.6 million km2) at an average density of 1 sample site/2500 km2. The resulting more than 2 x 2000 soil samples were air dried, sieved to <2 mm and analysed for their Hg concentrations following an aqua regia extraction. Median concentrations for Hg are 0.030 mg/kg (range: <0.003–1.56 mg/kg) for the Ap samples and 0.035 mg/kg (range: <0.003–3.12 mg/kg) for the Gr samples. Only 5 Ap and 10 Gr samples returned Hg concentrations above 1 mg/kg. In the geochemical maps the continental-scale distribution of the element is clearly dominated by geology. Climate exerts an important influence. Mercury accumulates in those areas of northern Europe where a wet and cold climate favours the build-up of soil organic material. Typical anthropogenic sources like coal-fired power plants, waste incinerators, chlor-alkali plants, metal smelters and urban agglomerations are hardly visible at continental scales but can have a major impact at the local-scale

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

Over 4000 agricultural and grazing land soil samples were collected for the “Geochemical Mapping of Agricultural and Grazing Land Soil of Europe” (GEMAS) project carried out by the EuroGeoSurveys Geochemistry Expert Group. The samples were collected in 33 European countries, covering 5.6 million km² at 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

GEMAS: adaptation of weathering indices for European agricultural soil derived from carbonate parent materials

Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur on a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, and which is useful for evaluating chemical weathering trends (e.g. the Chemical Index of Alteration (CIA) or the Mafic Index of Alteration (MIA)). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source-rock types at the continental scale, and allows a more robust interpretation of soil parent-material weathering grade and its impact on the current chemical composition of soil. An increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na, and precipitation of Fe-oxides and hydroxides. The relation between soil weathering status and its spatial distribution in Europe provides important information about the role played by climate and terrain. The geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination

Geogenic and agricultural controls on the geochemical composition of European agricultural soils

Concern about the environmental impact of agriculture caused by intensification is growing as large amounts of nutrients and contaminants are introduced into the environment. The aim of this paper is to identify the geogenic and agricultural controls on the elemental composition of European, grazing an nd agricultural soils