Background values — cadmium, Total mean content (upper soil)

Soils originated in thousands of years due to the interaction of diverse natural processes. For centuries, however, they have been increasingly shaped by human activities such as land use and substance inputs. For most inorganic substances, the base substrate of soil formation determines the natural (geogenic) basic content of a soil. In addition, there is an anthropogenic component, whereby the ratio of geogenic and anthropogenic proportion varies greatly depending on the element. Background values characterise the typical background content of a substance or group of substances in the soil. In accordance with the procedure of the Federal-Länder Working Group Soil Protection (LABO), statistical parameters are the 50. Percentile (median) and the 90th. Percentile. The median represents the middle background content, the 90. Percentile is the upper limit of the typical background content. For the purpose of determining background contents, the anthropogenic proportion must not come from an identifiable individual source or a single cause of stress. Rather, they must be diffuse, i.e. they must be the result of general large-scale (ubiquitous) and long-term material distributions. Therefore, before calculating background values, specifically polluted soils must be removed from the data. The substrate is the most important differentiation criterion for natural content of inorganic substances. The next deeper level of division are horizontal groups such as upper and subsoil as well as subsurfaces. If then there is a sufficient number of cases, the group of upper soil horizons is further divided into utilisation classes. For many years, the Land Office for Geology and Mining Rhineland-Palatinate has been involved in physical and chemical investigations of the soils as well as through cooperation with other state authorities. The information bases were significantly improved with data collected during the Rhineland-Palatinate soil load cadastre. Since this project, extensive soil surveys have been successively continued with the Rhineland-Palatinate soil status report. This long-term project of the Ministry of Environment, Forestry and Consumer Protection is carried out on behalf of the State Office for the Environment, Water Management and Trade Supervision. Meanwhile, about 18 % of the country’s surface area is covered with at least one site per km². The data base for the spatial distribution of substrate groups comes from the technical information system soil (FISBO) of the LGB. This system manages data derived from boch heterogeneous soil mapping (scale level 1:25,000 to 1:200,000). This leads to noticeably different resolutions and delimitation problems, for national surveys in the small-scale application above the scale of 1: However, 50,000 of these data are suitable despite their inhomogeneity. Further information on this topic can be found in the loose leaf collection >Background values of the soils of Rhineland-Palatinate< http://www.mwkel.rlp.de/Bodenschutz/Vorsorgender-Bodenschutz/Hintergrundwerte-der-Boeden Terms of use see: http://www.lgb-rlp.de/karten-und-produkte/online-karten/nutzungsbedingungen-fuer-online-karten.html:Als means the median (synonym: 50. Percentile, central value) used. It is the value above or below which 50 % of all cases of a data group are located. The calculation is carried out on outlier-adjusted data collectives. The total content is determined from the royal water extract (according to DIN ISO 11466 (1997)). The concentration is expressed in mg/kg. The salary classes take into account, inter alia, the pension values of the BBodSchV (1999). These are at 0.4 mg/kg for the soil type sand, for clay, sludge and heavy slurry sand at 1.0 mg/kg and for clay at 1.5 mg/kg. According to LABO (2003), a sample number of >=20 is required for the calculation of background values. The map also shows groups with a sample number >= 10. This information is then only informal and not representative.