GcBÜK400 — Zinc in the upper floor

Zinc is an essential trace element for plants, animals and humans, which, however, can have a toxic effect on plants and microorganisms at extremely high levels. The concentration of Zn in the upper continental crust (Clark value) is 52 mg/kg, but it can vary greatly depending on the type of rock. The mean Zn (median) grades of the Saxon main rock types range from 11 to 140 mg/kg, while the regional Clarke of the Ore Mountains is approximately 79 mg/kg. Sphalerite (zinc aperture) leading polymetallic lathers can locally lead to additional geogenic Zn enrichments in the soils. Anthropogenic Zn entries are mainly carried out by iron and non-ferrous metallurgy or by the Zn-processing industries (colours, alloys, electroplating) and by large combustion plants. In the area of agglomerations, Zn enrichments are relatively common. Anthropogenic Zn entries are possible in agriculture through the use of organic and mineral fertilisers. For uncontaminated soils, Zn levels of 10 to 80 mg/kg are considered normal. The regional distribution of the Zn content in the Saxon soils is mainly determined by the geogenic embossing of the substrates; low to medium grades can be expected over the periglacial sands and clays in the north and the loess soils in middle axes (10 to 50 mg/kg) and weathering soils above the solid rocks of the Ore Mountains/Vogtland (50 to 150 mg/kg). Within the basement units, significant positive Zn anomalies occur via the polymetallic deposits of the Ore Mountains, depending on the intensity of the mineralisation (Freiberg, Annaberg-Buchholz — Marienberg, Aue — Schwarzenberg). Soils over substrates with extremely low Zn content (Granite of Eibenstock, Orthogneise of the Ore Mountains Central Zone, Easter Mountain Eruptive Complex, Cretan sandstones) appear as negative Zn anomalies in the map image. Reinforced Zn accumulators are to be detected in the floodplain floors of the trough system. Due to the higher geogenic basic contents in the water catchment area, the occurrence of Zn-conducting polymetallic minerals and in particular the mining and metallurgical activity in the Freiberg region, high concentrations of Zn (median content 370 and 240 mg/kg respectively) occur mainly in the meadows of the Freiberger and United Mulde. No test and measure values have been established for the soil-human and soil-plant effects pathways for total levels in the Federal Soil Protection and Contaminant Ordinance (BBodSchV), as Zn is of little importance in the risk assessment.