GEMAS: colours of dry and moist agricultural soil samples of Europe

High resolution HDR colour images of all Ap samples from the GEMAS survey were acquired using a GeoTek Linescan camera. This data set will help to develop new methods for world-wide characterization and monitoring of agricultural soils which is essential for quantifying geologic and human impact on the critical zone environment

GEMAS: CNS concentrations and C/N ratios in European agricultural soil

A reliable overview of measured concentrations of TC, TN and TS, TOC/TN ratios, and their regional distribution patterns in agricultural soil at the continental scale and based on measured data has been missing – despite much previous work on local and the European scales. Detection and mapping of natural (ambient) background element concentrations and variability in Europe was the focus of this work. While total C and S data had been presented in the GEMAS atlas already, this work delivers more precise (lower limit of determination) and fully quantitative data, and for the first time high-quality TN data

GEMAS: unmixing magnetic properties of European agricultural soil

High resolution magnetic measurements provide new methods for world-wide characterization and monitoring of agricultural soil which is essential for quantifying geologic and human impact on the critical zone environment and consequences of climatic change, for planning economic and ecological land use, and for forensic applications. Hysteresis measurements of all Ap samples from the GEMAS survey yield a comprehensive overview of mineral magnetic properties in European agricultural soil on a continental scale

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

London region atlas of topsoil geochemistry

The London Region Atlas of Topsoil Geochemistry (LRA) is a further step towards understanding the chemical quality of soils in London, following a previous project called London Earth carried out by the British Geological Survey (BGS) (Johnson et al., 2010[1]). The main advantage of the LRA is that it includes soil geochemical data from the counties surrounding London; placing the city within the context of its rural hinterland, allowing assessments of the impact of urbanisation on soil quality. The London Region Atlas of Topsoil Geochemistry is a product derived from the BGS Geochemical Baseline Survey of the Environment (G-BASE[2]) project. The London Region Geochemical Dataset (LRD, n=8400), on which the atlas is based, includes TOPSOIL data from two complementary surveys: i) the urban London Earth (LOND) and ii) the rural South East England (SEEN). The LRA covers the Greater London Authority (GLA) and its outskirts in a rectangular area of 80x62 km. This extends from British National Grid coordinates Easting 490000–570000, and Northing 153000–215000. The urban LOND and the rural SEEN surveys contribute with 6801 and 1599 samples respectively to the LRD. The concentrations of 44 inorganic chemical elements (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2, TiO2, Ag, As, Ba, Bi, Br, Cd, Ce, Co, Cr, Cs, Cu, Ga, Ge, Hf, I, La, Mo, Nb, Nd, Ni, Pb, Rb, Sb, Sc, Se, Sn, Sr, Th, U, V, W, Y, Zn and Zr), loss on ignition (LOI) and pH in topsoil are included in the LRA. For each element, a map showing the distribution in topsoil across the atlas area and a one-page sketch of descriptive statistics and graphs are presented. Statistics and graphs for whole dataset (LRD), London urban subset (LOND) and London surroundings rural subset (SEEN), as well as graphs of topsoil element concentrations over each simplified geology unit are shown. The LRD has been used already in a study aiming to detect geogenic (geological) signatures and controls on soil chemistry in the London region (Appleton et al., 2013[3]). It includes maps showing the distribution of Al, Si, La and I (and Th, Ca, Mn, As, Pb and Zr in supplementary material) and it is concluded that the spatial distribution of a range of elements is primarily controlled by the rocks from where soil derives, and that these geogenic patterns are still recognisable inside the urban centre. Other studies have been done that are based on data in the LRD, namely using the LOND subset or part of it. The main focus of these studies was the mercury content (Scheib et al., 2010[4]), the influence of land use on geochemistry (Knights and Scheib, 2011[5]; Lark and Scheib, 2013[6]); the bioaccessibility of pollutants such as As and Pb (Appleton et al., 2012[7]; Appleton et al., 2012[8]; Cave, 2012[9]; Appleton et al., 2013[10]; Cave et al., 2013[11]) and the lability of lead in soils (Mao et al., 2014[12]); the determination of normal background concentrations of contaminants in English soil (Ander et al., 2013[13]) and the contribution of geochemical and other environmental data to the future of the cities (Ludden et al., 2015[14]). The London Region Atlas of Topsoil Geochemistry formally presents detailed information for all chemical elements in the LRD. This information can be easily visualised and elements compared as its production and layout is standardised. Differences in topsoil element concentrations between the centre of the city and its outskirts can be assessed by observing the map and comparing statistics and graphs reported for the LOND and SEEN subsets respectively. This urban/rural contrast is particularly evident for elements such as Pb, Sb, Sn, Cu and Zn, for which mean concentrations in the urban environment are two to three times higher than those observed in the rural environment. This is a typical indicator suite of urban soil pollution reported in several other cities in the UK also (Fordyce et al., 2005[15])

The collection of drainage samples for environmental analyses from active stream channels

The collection of drainage samples from active stream channels for geochemical mapping is now a well-established procedure that has readily been adapted for environmental studies. This account details the sampling methods used by the British Geological Survey in order to establish a geochemical baseline for the land area of Great Britain. This involves the collection of stream sediments, waters and panned heavy mineral concentrates for inorganic chemical analysis. The methods have been adapted and used in many different environments around the world. Detailed sampling protocols are given and sampling strategy, equipment and quality control are discussed

Use of GEMAS data for risk assessment of cadmium in European agricultural and grazing land soil under the REACH Regulation

Over 4000 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. Cadmium concentrations are reported for the <2 mm fraction of soil samples from regularly ploughed fields (agricultural soil, Ap, 0 - 20 cm, N - 2218) and grazing land soil (Gr, 0 - 10 cm, N - 2127)

Distribution and mobility of Niobium in European soils

The EuroGeoSurvey’s Geochemical Mapping of Agricultural and Grazing Land Soil (GEMAS) project and its 32 participating organisations mapped European soils at a density of 1 site per 2,500 km2 providing geochemical data for over 50 elements (EGS, 2008). At each site, two types of soils were collected, one “Ap” sample from the ploughing layer of arable fields at 0-20 cm and one “Gr” sample from permanent grazing land at 0-10 cm below surface. Analyses of the < 2 mm fraction of 2024 Gr and 2108 Ap samples were carried out by a) inductively coupled plasma atomic emission spectrometer (ICP-AES) and inductively coupled plasma emission mass spectrometer (ICP-MS) following aqua regia extraction as well as b) X-ray fluorescence spectrometry (XRFS) on Gr samples only. Whilst the latter method gives the total concentration, aqua regia gives only the chemically extractable fraction. The refractory element Niobium (Nb) is of growing interest because of its application and use as an alloying element in high-grade structural steel, as well as in electronic components. However, there is very little published information on Nb concentration levels in the environment and its potential health effects. GEMAS data for Nb is presented with the aim to establish and enhance our understanding of the baseline distribution and typical mobility within European soils. The median baseline concentration of Nb in Gr soils of Europe is 12 mg/kg (XRFS), which is more than a magnitude greater than the median of 0.52 mg/kg following aqua regia extraction and ICP analyses. This shows that a large proportion (>95%) of Nb in soils is highly immobile. Comparing the chemically mobile concentration, determined by ICP following aqua regia extraction in Gr and Ap (collected from the same sampling cells), shows that the median concentration in Gr soils is 0.07 mg/kg (13%) higher than in Ap soils. This relative depletion of aqua regia-soluble Nb in Ap soils may be a result of physical agricultural practises, such as tillage. Across Europe, elevated concentrations of chemically mobile Nb are closely related to the occurrence of Caledonian granitic and plutonic rocks in Scandinavia and northern Britain, Hercynian granites across the European continent (e.g. Massif Central and Bohemian Massif) as well as carbonate rocks of southern Italy. The larger resistant and immobile portion of Nb in soils however, is more spatially dispersed and not only confined to areas of plutonic outcrop. Elevated concentrations (>15 mg/kg) also occur across areas of known aeolian sediments, such as loess of central Europe, and residual soils related to karstified carbonate rocks across Croatia and Slovenia

London Earth : anthropogenic and geological controls on the soil chemistry of the UK’s largest city

The soil geochemical survey of the Greater London (UK) area, comprising over 6400 sample sites, is the most detailed and comprehensive urban mapping project carried out to date. In order to give insight into the environmental impacts of urbanisation and industrialisation, as well as to characterise the geochemical baseline of the UK’s most populous city, samples were collected at a density of 4 sites per km2. The <2 mm fraction from the topsoil samples (5 – 20 cm) was analysed by X-ray fluorescence spectrometry (XRFS). Resulting data for over 50 elements were subject to rigorous quality control procedures to ensure accurate and inter-comparable data. Anthropogenic modification to soil baseline concentrations is evident across the urban area. A notable feature is the ‘central zone’ of higher concentrations of, for example, Pb, Sb, Ca, Zn, Cu, Sn and As in the oldest, most intensely urbanised parts of the city. In the cases of Pb and Sb in particular, high-density traffic is a likely source. Local ‘hotspots’ of elevated concentrations, related to particular anthropogenic activities, can also be identified. For example Se, Cd, Ni, Cu and Zn show particularly elevated concentrations in the vicinity of an industrial area on the banks of the river Lee in north London, whilst Cr and Cd also display high concentrations around Heathrow airport in the west. Despite these anthropogenic controls, a strong geological control on soil chemistry is observed for many elements. This is particularly evident in south London where high baseline concentrations of, for example, Ca, Ce, I, La, Mn, Nd, P, Sr, Y and Zr, relate to the influence of the Cretaceous chalk bedrock. In the north-western quadrant of London and along the northern boundary of the project area, high baseline concentrations for a number of elements (Al, Fe, Mg, K, Cr, La, Ti, Ga, Rb and Ni) are associated with the outcrop of Palaeogene clays. Elevated levels of Hf and Zr correspond to areas of Eocene marine and Quaternary wind-blown deposits. One of the most interesting features of the mapped data is the consistently low concentrations of metals associated with the Royal Parks (Bushy and Richmond), Hampton Court and nearby Wimbledon Common in southwest London, which contrast with surrounding areas. Throughout the urban evolution of London these parks have avoided significant residential or industrial activity and remain free of imported soil, wastes or ‘made ground’. Consequently, comparison of geochemical baselines within and outside the parks, where underlying geology is consistent, can help to provide an indication of ambient anthropogenic geochemical modification of London’s soils