Hydrogeological overview map of Lower Saxony 1 : 500 000 - Groundwater quality: Iron content

Description

The hydrogeological overview map of Lower Saxony 1 : 500 000 - Groundwater quality: Iron content shows the evaluation of a representative selection of iron concentrations from the laboratory database of the LBEG. The data collected over a period from 1967 to 2000 were averaged twice. In the case of groundwater measuring stations with multiple analyses, mean values of the available test results were calculated. In addition, the values of all sampling points within a radius of 2000 m were subjected to further averaging. The classification of the classes takes into account the limit value of the Drinking Water Ordinance (TVO) of 0.2 mg/l. Increased concentrations, which are clearly due to point-like anthropogenic inputs (e.g. old landfills), are not reflected in this overview map. The iron contents are shown in depth steps without reference to the local hydrogeological situation. The bar charts in the example shown on the right reflect results for depth levels up to 20 meters, over 20 to 50 meters, over 50 to 100 meters and over 100 to 200 meters. A comparison of values is therefore not permissible without taking into account the respective hydrogeological situation (e.g. hydrogeological floor construction) as well as the use of the data for detailed investigations. The concentration of iron in groundwater is strongly influenced by the pH value and the redox ratios. The highest iron content in Lower Saxony is achieved in acidic and/or strongly reduced water. On the other hand, high concentrations of carbonate and sulfide ions cause the precipitation of siderite or iron sulfides and thus limit the solubility of iron. At high concentrations of dissolved organic carbon, large amounts of iron are also bound to organocomplexes. In general, the iron content in the hard rock aquifers of the Lower Saxony mountains is significantly lower than in quaternary loose rocks. Mesozoic limestones have the lowest iron concentrations from 0.01 to a maximum of 0.1 mg/l. Higher values are observed in Mesozoic sandstone. In the paleozoic rocks of the Harz, there are values in the range of 0.1 - 0.5 mg/l. The oxygen-containing groundwater in northern Lower Saxony (e.g. Lüneburg Heath) shows iron concentrations in the range of 0.1 - 1 mg/l. In rare cases, up to 2 mg/l is achieved. In the lowlands in northern Lower Saxony, the limit value of the TVO of 0.2 mg/l is often exceeded. Iron concentrations of 2 – 10 mg/l are often observed in rising groundwater with longer flow paths. Also very high iron contents between 10 and 40 mg/l can be found in the groundwater, which is influenced by bogs (e.g. Vehnemoor southwest of Oldenburg and Teufelsmoor north of Bremen). On the other hand, iron-bearing groundwaters in the north of Hanover (Isernhagen, Langenhagen) with concentrations of up to 40 mg/l are probably due to the oxidation of pyrite from lower chalk claystone.

Resources

Name Format Description Link
0 https://nibis.lbeg.de/net3/public/ogc.ashx?NodeId=643&Service=WMS&Request=GetCapabilities&

Tags

  • opendata
  • inspireidentifiziert
  • nibis-metadaten
  • sgd_hydrogeologie

Topics

  • TECH

Categories