Background values for Cobalt (Co) 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.2017年，LABO发布了涵盖16种重金属与微量元素的全国土壤背景值数据集。该数据集基于经德国联邦地球科学与自然资源研究院（BGR）联合均质化处理的王水提取物（aqua regia extracts）剖面描述（profile descriptions）与测量数据。为避免高定量限的测量数据对背景值推导产生干扰，研究团队依据特定标准将其剔除，未纳入后续评估环节。为防止样品密度较高的区域对背景值造成非均衡影响，研究团队对部分数据实施了空间稀疏化（spatial thinning）处理。研究人员通过深度加权平均法（depth-weighted averages），将单个采样点多个土壤发生层（horizons）的测量值合并为单一数值。评估阶段，所有可用测量值被划分为不同的土壤母质（soil parent materials）组别。此外，还依据采样深度将样品划分为表土层（topsoil）、心土层（subsoil）与地下层（underground）三类。针对表土层样品，评估过程还需兼顾不同土地利用（land use）类型的差异，包括耕地、草地与林地。鉴于德国南北部松散岩类（unconsolidated rocks）的组成存在显著差异，研究团队对其分别开展评估。但在将数据集划分为子集合（sub-collectives）后，并非所有组别均可获得可靠的样本量（case numbers）。因此，本次仅展示样本量≥20的背景值数据集。其完整推导流程可参阅LABO-Bund/Länder-Arbeitsgemeinschaft Bodenschutz（2017）发布的官方报告：《土壤中无机与有机物质背景值》（第4次修订增补版）。