Background values – HGW: Lead, 90.Percentile (information in mg/kg)

Soils were created in thousands of years by the interaction of diverse natural processes. For centuries, however, they have increasingly been characterised by human activities such as land use and material inputs. For most inorganic substances, the initial substrate of soil formation largely determines the natural (cooked) base content of a soil. In addition, there is an anthropogenic component, whereby the ratio of geogeneous and anthropogenic proportions varies greatly. Background values characterise the typical background contents of a substance or group of substances in the soil. In accordance with the procedure of the Federal-Länder Working Group on Soil Protection (LABO), the statistical parameters are 50. Percentile (median) and the 90th. Percentile used. The median represents the average background content, the 90. Percentile represents the upper limit of the typical background content. For the purpose of determining the background content, the anthropogenic proportion must not come from an identifiable single source or a single cause of exposure. Rather, they must be diffuse, i.e. they must be the result of general large-scale (ubiquitous) and over longer periods of material distributions. Prior to the calculation of background values, specifically contaminated soils must therefore be removed from the data. The substrate is the most important differentiation criterion for natural content of inorganic substances. The next deeper plane of divisions are horizon groups such as upper and subsoil as well as subsoil. If there is still a sufficient number of cases, the group of upper-soil horizons is further subdivided into usage classes. For many years, the Rhineland-Palatinate State Office for Geology and Mining has been involved in physical and chemical investigations of soils as well as through cooperation with other state authorities. The information bases were significantly improved with data collected during the Rhineland-Palatinate soil pollution cadastre project. Since this project, the Rhineland-Palatinate soil status report has been progressively continuing extensive soil investigations. This long-term project of the Ministry of the Environment, Forestry and Consumer Protection is carried out on behalf of the State Office for the Environment, Water Management and Trade Inspectorate. Meanwhile, about 18 % of the country’s area with at least one site per km² is covered. The data base on the spatial distribution of the substrate groups comes from the specialised information system Boden (FISBO) of the LGB. This system manages data derived from heterogeneous soil maps (scale level 1:25.000 to 1:200.000). Although this leads to noticeably different resolutions and demarcation problems, for nationwide surveys in small-scale applications above the scale of 1: However, 50.000 these data are suitable despite their inhomogeneity. Further information on this topic can be found in the Loteblatt collection background values of the soils of Rhineland-Palatinate.:As 90.P background value is 90. Percentile of a data collective. It is the value in which 90 % of the cases observed so far have lower levels. The calculation is carried out after cleaning the data group of outliers. The 90th. Percentile often serves as the upper limit of the background range to delineate unusually high grades. The total content is determined from the royal water extract (according to DIN ISO 11466 (1997)). The concentration is given in mg/kg. The salary classes take into account, inter alia, the pension values of the BBodSchV (1999). These are at 40 mg/kg for the soil type sand, for clay, silt and heavy sluggish sand at 70 mg/kg and for clay at 100 mg/kg. According to LABO (2003), a sample count of >=20 is required for the calculation of background values. However, groups with a sample count >= 10 are also shown in the map. This information is then only informal and not representative.