GcBÜK400 — Chrome in the upper floor
Description
Chromium is a common element found in many minerals, which is vital for humans and animals. It exists in several oxidation stages, but only the three- and hexavalent compounds are stable in the soil. Uncontaminated soils have chromium levels between 5 and 100 mg/kg. The regional Clarke of the Ore Mountains is 52 mg/kg (total content). Chromium is entered anthropogenically into the environmental media via the metallurgy and Cr-processing industries (colours, alloys, catalysts, pickling, polishing agents, construction industry). In the soils there can still be an additional load with chromium due to fertilisation (Cr in Thomasphosphate) and sewage sludge application. The regionally different distribution of chromium in the Saxon soils results from the geogenic specialisation of the substrates. In soil formation, there is no greater accumulation or depletion of chromium. The contents of the soils are about the level of the starting rocks. In the northern and north-western parts of the country, low chromium levels below 20 mg/kg dominate in the soils over largely sandy loose rocks. The soils over acidic magmatites and metamorphites as well as over the sandstones of the Elbtalk and the granodiorites of the Lausitz are also in the lower range. Chromium levels in soils increase to about 30-40 mg/kg via the loosely influenced looser sediments, the Rotlieged sediments as well as the clay slates, phyllites, mica slates and paragn irons of the Ore Mountains. The highest grades (100 mg/kg) occur in Saxony via basic vulcanites (basaltes, serpentinites, gabbros), over the larger areas forming diabasses of the Vogtland and locally via mineralisation containing Cr and weathering (Ni-hydrosilicates in St. Egidien). Serpentinites, for example, may contain up to 2 000 mg/kg of chromium (total content). In the floodplains there are clear relationships between the chromium levels and the rocks of the respective catchment areas. The floodplains of the White Elster, the Mulde and the Elbe (Ore Mountains/Vogtland catchment area) produce medium to slightly increased grades. On the other hand, the levels in the floodplains of the Lausitz are significantly lower. Due to the different binding forms of chromium in the primary substrates, the conversion of Cr total contents into Cr-king water content (KW) is extremely problematic. Practical experience in soil studies shows that the KW levels of basic to ultrabasic magmatites and metamorphites are up to about 50 % lower compared to total levels. The geochemical specialisation of the basic substrates therefore only appears in a weakened form in the map image. The test values set out in the Federal Soil Protection and Contaminant Ordinance (BBodSchV) for the soil-human (KW content) trajectory pathway in Saxony are only exceeded selectively via the above-mentioned basic and ultra-basic rocks. In Vogtland it is sometimes possible to exceed the Cr precautionary values via the diabasene, although due to the natural form of binding no increased release in the soil can be expected.
Resources
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https://luis.sachsen.de/boden/geodatendownload.html |