Background values for Molybdenum (Mo) in German soils 1:1,000,000

New, nationwide background values for 16 heavy metals and trace elements were published by the LABO in 2017. They are based on profile descriptions and measurements of aqua regia extracts, which were combined and homogenized by the BGR. Measurements with high quantification limits were excluded from further evaluation according to certain criteria in order to avoid their influence on the derivation of background values. To prevent the background values from being disproportionately influenced by regions with high sample densities, spatial thinning was partially performed. The values of several horizons of a site were combined to one value by depth-weighted averages. For evaluation, the available measured values were assigned to different groups of soil parent materials. In addition, a distinction was made whether the samples were taken in the topsoil, in the subsoil or in the underground. In the case of topsoil, the different land use (arable land, grassland, forest) was also taken into account for the evaluation. Unconsolidated rocks were evaluated separately for northern and southern Germany due to their different composition. By dividing the data into sub-collectives, reliable case numbers were not achieved in all cases. Consequently, only background values with case numbers ?20 are presented. The exact derivation procedure can be found in the report of the LABO-Bund/Länder-Arbeitsgemeinschaft Bodenschutz (2017): 'Hintergrundwerte für anorganische und organische Stoffe in Böden', 4th revised and supplemented edition.德国土壤保护联邦州工作组（LABO）于2017年发布了针对16种重金属与微量元素的全新全国性土壤背景值数据集。该数据集基于王水（aqua regia）提取物的剖面描述与检测结果，相关数据已由德国联邦地球科学与自然资源研究所（BGR）完成整合与均质化处理。为避免高定量限的检测结果对背景值推导造成干扰，研究团队依据既定标准将此类数据排除在后续评估之外。为防止高采样密度区域对背景值产生过度影响，研究人员对数据进行了部分空间抽稀处理。针对同一采样点的多个土层发生层，研究团队采用深度加权平均法将其整合为单一数值。评估阶段，所有可用检测数据被划分为不同的土壤母质类别。此外，研究还依据采样深度将样本区分为表土层、心土层与地下岩层样本。针对表土层样本，评估过程还需考虑耕地、草地、林地等不同土地利用类型的影响。由于德国南北部未固结岩石的组成存在显著差异，研究人员针对该类岩石分别开展了北部与南部区域的独立评估。尽管将数据划分为多个子数据集，但并非所有类别均能获得足够可靠的样本量。因此，本次仅公布样本量≥20的背景值结果。详细的背景值推导流程可参阅德国土壤保护联邦-州工作组（LABO-Bund/Länder-Arbeitsgemeinschaft Bodenschutz）2017年发布的《土壤中无机与有机物质背景值》（第4次修订增补版）报告。