GcBÜK400 — arsenic in the upper floor

Arsenic is a semi-metal, ubiquitous and toxic element. It is widely found in nature in various mineralisations as arsenic sulphide or oxide and as copper, nickel and iron arsenate. The average As content of the rocks of the upper continental crust (Clark value) is 2 mg/kg. In the literature, As levels 20 mg/kg are described as normal levels, the mean content being about 5 mg/kg. Among the toxic elements, the arsenic is particularly important due to its large spread of increased content in Saxon soils. The causes are undoubtedly to be found in the geochemical-metallogenetic specialisation of the Fichtelgebirgisch Erzgebirgic Anticlinal Zone. The area-related mean A content of the main rock types (petrogeochemical component) is approximately 13 mg/kg. The chalkogenic component is of particular importance in the Ore Mountains. In addition to the element enrichment in the mineralisation itself, which was the subject of mining, there was also a large-scale influence on the side rocks or their weathering products (primary and secondary geochemical aureoles). The anthropogenic influence of natural soils is mainly due to the ore treatment plants and the emissions of non-ferrous metalworks. Whereas low levels dominate in the upper soils of North and in parts of central axis (as-poor periglaciary sandy to loamy substrates; Löss), a relative enrichment occurs in the weathering soils via solid rocks as a result of the higher petrogenic A component. Important regional anomalies are mainly located in the Freiberg region (Osterzgebirge), the most important site of mining and the smelting of polymetallic ores, as well as in the West Ore Mountains (Aure — Ehrenfriedersdorf area). The great extent and intensity of the spread of As minerals in polymetallic, tin-tungsten and bi-co-Ni-Ag-U ore formations, as well as their prevention, led to large-scale geogenic and anthropogenic enrichments. Both areas are separated by the north-south-souting Flöha zone, an area in which hardly any ore mineralisations occur and thus the chalkogenic component is rarely developed. Large-area elevated As levels in soils of the Vorerzgebirgssenke (Zwickau — Chemnitz) are due to the geochemically specialised rotary sediments (including removal products of the Ore Mountains). Particularly high levels of As are common in the meadows of the Freiberger Mulde, Zschopau, Zwickauer Mulde and the United Mulde. Due to the geological process of the removal of soils from the ore-mounted deposits as well as anthropogenic inputs by the ore processing and metallurgy industry, the deposit of the river sediments and swine parts in the flooding areas leads to constant as-enrichment in the floodplains. As a result of the geogenic and anthropogenic processes described above, the test and measure values of the Federal Soil Protection and Contaminant Ordinance (BBodSchV) for arsenic are sometimes exceeded.