Background values for Lead (Pb) 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.德国联邦与各州土壤保护工作组（LABO）于2017年发布了针对16种重金属与微量元素的全新全国土壤背景值数据集。该数据集基于由BGR（德国联邦地质与原材料研究所）整合均质化的王水提取液土壤剖面描述与测量数据构建。为避免高定量限的测量结果对背景值推导造成干扰，研究人员依据特定标准将其剔除于后续评估流程之外。为防止样本密度较高的区域对背景值产生过度影响，研究团队对数据进行了局部空间稀疏化处理。将单个采样点的多个土壤发生层测量值通过深度加权平均法合并为单一数值。评估阶段，可用测量数据被划分为不同的土壤母质组别；此外，还根据采样深度将样本分为表层土壤、亚表层土壤与地下层三类。针对表层土壤样本，研究人员同时纳入耕地、草地、林地等不同土地利用类型作为评估考量因素。鉴于德国南北部松散岩类的组成存在显著差异，研究人员对其分别开展了独立评估。将数据集划分为子数据集后，并非所有分组均可获得可靠的样本量，因此本次仅公布样本量不低于20的背景值结果。背景值的具体推导流程可参考LABO-Bund/Länder-Arbeitsgemeinschaft Bodenschutz（2017）发布的报告《土壤中无机与有机物质背景值》（第4次修订增补版）。