Sulphate soils in Lower Saxony’s coastal areas 1: 50 000 — Depth range 0-2 m

This map shows the risk of spreading current and potentially sulphate acid soils from 0 to 2 m depth. Important: This map has been reworked using the new BK50 soil map, for which the relevant coastal areas have been mapped in particular. Therefore, there can be significantly different assessments than in the previous map of sulphate acid soils (deep range 0-2 m). The explanatory Geofacts 24 are currently under revision. So-called “sulfate sour soils” are found in Lower Saxony, especially in the coastal areas. This designation includes both soils and deeper sediments as well as peat. Characteristic of the various sulphate acid materials (SSM) are high, geogenic content of reduced inorganic sulphur compounds. Originally, the sulphur in the form of sulfations from the sea water entered the holocene deposits. Due to water-saturated, anaerobic conditions, sulphide was reduced and preserved for a long time as pyrite and FeS due to constant high groundwater levels. Typical SSMs are clay-rich materials with higher levels of organic matter and/or coarse plant residues as well as over- and slicked low mooror feces. Dewatering and ventilation of these materials results in the oxidation of sulphides and the formation of sulphuric acid, e.g. when they are dewatered or removed from the natural compound as part of construction projects. From potentially sulfate-acid soils, sulfate-acid soils can thus become presently. The high risk potential is due to: • Extreme acidification (pH < 4.0) of the dredging material resulting from plant damage, • Significantly increased sulphate concentrations in soil water or leachate, • Increased availability or solubility of heavy metals and increased concentrations in leachate; • High risk of corrosion for concrete and steel structures. For security and/or minimisation, all construction measures involving excavation or groundwater reductions in the affected areas require detailed technical planning and support. It should be noted that the spread of iron sulphides in the surface and depth is often rather stained. Therefore, the identification of current and potentially SSM as well as construction planning and support should only be carried out by qualified specialists in soil science. Due to the often low load capacity of these soils and in particular the peat, relatively large excavation pits have to be excavated in a short time. In addition, oxidation and acidification often occur very quickly. This evaluation map can already be used during the planning and designation of areas, e.g. in the context of route planning, land use and development plans, etc. Concrete instructions for construction planning and support as well as on sampling and laboratory analysis of the SSM to be relocated can be found in Geofakten 25. Attention: The map is only the basis for a concrete exploration at the site of the construction project.