Hydrogeological overview map of Lower Saxony 1: 500 000 — Groundwater quality: Iron content (WMS service)

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 have been averaged twice. For groundwater measuring points with multiple analyses, mean values of the available test results were formed. In addition, the values of all sampling points in a radius of 2 000 m were subjected to further averaging. Classes are classified taking into account the limit values of the Drinking Water Ordinance (TVO) of 0.2 mg/l. Increased concentrations, which are clearly due to point-shaped anthropogenic entries (e.g. old landfills), are not reproduced in this overview map. The iron content is shown at depth levels without reference to the local hydrogeological situation. The rod diagrams in the example shown on the right reflect results for the depths 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 examinations. The concentration of iron in groundwater is strongly influenced by pH and redox ratios. The highest iron content in Lower Saxony is achieved in acidic and/or greatly reduced water. On the other hand, high concentrations of carbonate and sulphide ions cause the precipitation of siderite or iron sulphides, thus limiting the solubility of iron. At high concentrations of dissolved organic carbon, large proportions of iron are also bound to organocomplexes. In general, the iron content in the solid rock equifers of the Lower Saxony mountain region is significantly lower than in quaternary loose rocks. Mesozoic limestones contain the lowest iron concentrations of 0.01 to a maximum of 0.1 mg/l. Higher values are observed in mesozoic sandstone. In the paleozoic rocks of the resin 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 are 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 ascending groundwater with longer flow paths. Also very high iron content between 10 and 40 mg/l can be found in groundwater, which is influenced by moors (e.g. Vehnemoor southwest of Oldenburg and Teufelsmoor north of Bremen). By contrast, iron-containing groundwaters in the north of Hanover (Isernhagen, Langenhagen) with concentrations of up to 40 mg/l are likely to be traced back to the oxidation of pyrite from lower chalk claystone.下萨克森州1:50万水文地质概览图——地下水水质：铁含量，该图展示了基于下萨克森州地质、采矿与能源局（LBEG）实验室数据库中代表性铁浓度样本的评估结果。1967年至2000年间收集的数据集历经两次平均计算：对于存在多次分析结果的地下水监测点，先取其所有检测结果的平均值；此外，对半径2000米范围内所有采样点的数值进行二次平均。 本次分类以德国《饮用水条例》(TVO)规定的0.2mg/L限值作为依据。本概览图未标注因点状人为输入（如老旧填埋场）导致的浓度升高情况。铁含量按深度层级展示，未结合当地水文地质条件。右侧示例中的杆状图分别反映了20米以浅、20~50米、50~100米及100~200米深度区间的检测结果。因此，若未结合对应水文地质条件（如水文地质基底结构）以及该数据用于详细勘察的用途，则不得进行跨深度层的数值对比。 地下水中的铁浓度受pH值与氧化还原条件的强烈影响。下萨克森州的最高铁含量出现在酸性且/或强还原水环境中。反之，高浓度的碳酸盐与硫化物离子会诱导菱铁矿或硫化铁沉淀，从而限制铁的溶解度；当溶解态有机碳浓度较高时，大量铁会与有机络合物结合。 总体而言，下萨克森州山区的基岩含水层中铁含量显著低于第四系松散岩层。中生界石灰岩的铁浓度最低，仅为0.01~0.1mg/L；中生界砂岩的铁浓度更高。古生代岩层中的铁浓度范围为0.1~0.5mg/L。下萨克森州北部含氧地下水（如吕讷堡石楠草原）的铁浓度范围为0.1~1mg/L，极少数情况下可达2mg/L。在下萨克森州北部低地，《饮用水条例》(TVO)规定的0.2mg/L限值常被突破。 在径流路径更长的上升地下水中，常观测到2~10mg/L的铁浓度。在受沼泽影响的地下水中（如奥尔登堡西南的费讷沼泽与不来梅北部的魔鬼沼泽），也可发现10~40mg/L的极高铁含量。与之形成对比的是，汉诺威北部（伊瑟尔哈根、朗根哈根）的含铁地下水浓度最高可达40mg/L，其成因大概率为下白垩统黏土岩中的黄铁矿氧化作用。