GEMAS – Chemistry of Europe’s Agricultural soils, Supporting information, Population density

GEMAS (Geochemical Mapping of Agricultural and Grazing Land Soil in Europe) is a cooperative project between the Geochemistry Expert Group of EuroGeoSurveys and Eurometeaux. In total, more than 60 international organisations and institutions worldwide were involved in the implementation of the project. During 2008 and 2009, a total of 2219 samples of agricultural (arable land soils, 0 – 20 cm, Ap samples) and 2127 samples of grazing land (pasture land soils, 0 – 10 cm, Gr samples) soil were collected at a density of 1 site/2 500 km² each from 33 European countries, covering an area of 5,600,000 km². All samples were analysed for 52 chemical elements after an aqua regia extraction, 41 by XRF (total), TC and TOC. In the agricultural soil samples, 57 elements in a mobile metal ion (MMI®) extraction and Pb isotopes ratios were also analysed. In addition to the chemical element contents, soil properties and soil parameters such as pH, particle size distribution, effective cation exchange capacity (CEC), MIR spectra and magnetic susceptibility were investigated and some coefficients were calculated. All analytical results were subject to tight external quality control procedures. The GEMAS project thus provides for the first time fully harmonised data for element concentrations and bioavailability of the elements at the continental (European) scale. The geochemical maps provided in the data series “GEMAS - Single element maps” and “GEMAS - Parameters and indices” show an unbiased representation of the distribution patterns of the investigated elements and parameters. The data series “GEMAS - Supporting information” provides additional information to support the interpretation of these geochemical maps. The data set “Population density” belonging to this data series provides maps of population density in the project survey area (data source: CIESIN, 2018; CIESIN, CIAT, 2005).GEMAS（欧洲农业与牧场土壤地球化学制图，Geochemical Mapping of Agricultural and Grazing Land Soil in Europe）是由欧洲地质调查协会（EuroGeoSurveys）地球化学专家小组与欧洲金属监测协会（Eurometeaux）合作开展的项目。全球共有超过60个国际组织与机构参与了本项目的实施。 2008至2009年间，项目组从欧洲33个国家中，以每2500平方公里1个采样点的密度，采集了2219份农业土壤样品（耕地土壤，0–20cm，即Ap样品）与2127份牧场土壤样品（牧草地土壤，0–10cm，即Gr样品），覆盖总面积达560万平方公里。 所有样品均经王水消解后开展52种化学元素分析，其中41种元素采用X射线荧光光谱法（XRF，总含量）、总碳（TC）与总有机碳（TOC）完成检测。针对农业土壤样品，研究团队还额外开展了57种元素的可移动金属离子（MMI®）萃取分析以及铅同位素比值测定。 除化学元素含量外，项目组还对土壤性质与参数进行了调研，包括pH值、粒度分布、有效阳离子交换容量（CEC）、中红外光谱（MIR）以及磁化率，并计算了相关系数。所有分析结果均严格遵循外部质量控制流程。 因此，GEMAS项目首次在欧洲大陆尺度上，提供了统一协调的元素浓度与元素生物有效性数据集。 数据系列"GEMAS - 单元素制图"与"GEMAS - 参数与指数"中所载的地球化学图谱，客观呈现了所调研元素与参数的空间分布格局。数据系列"GEMAS - 辅助信息"可辅助解读上述地球化学图谱，其中包含的"人口密度"数据集展示了项目调查区域内的人口密度分布图谱（数据来源：CIESIN，2018；CIESIN、CIAT，2005）。