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

The Hydrogeological Overview Map of Lower Saxony 1: 500 000 — Groundwater quality: Chloride content shows the evaluation of a representative selection of chloride 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 categorised taking into account the de minimis threshold (GFS) or the limit value of the Drinking Water Ordinance (TVO) of 250 mg/l. Increased concentrations that are clearly due to point-shaped anthropogenic entries (e.g. waste landfills, mining dumps) are not reproduced in this overview map. The chloride content is shown at depth levels without reference to the local hydrogeological situation. 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 lowest concentrations of chloride in Lower Saxony are found in the Harz and Solling with 5-10 mg/l and in the Lüneburg Heath with 10-30 mg/l. Contents above 50 mg/l cannot be explained by the atmospheric input and the enrichment by evapotranspiration in general and are usually due to geogenic or anthropogenic salinisation of the groundwater. Very strong geogenic chloride salinisation of groundwater is found in Lower Saxony mainly on the coast and in the estuary of Elbe, Weser and Ems (coast salinisation by sea water) with concentrations of 15,000-16.000 mg/l. Outside the areas of seawater salinisation, the chloride levels are between 30 and 50 mg/l. Another cause of geogenic salinisation of groundwater is the blueness of salt rocks in the underground. An example of this is increased concentrations of chloride, which often occur in lowlands of rivers (e.g. Elbe near Lauenburg and Gorleben, Jeetzel, Wümme) and which are due to ascending agglomeration waters of salt structures. Also near Hannover (Ronnenberg, Sarstedt), Salzgitter, Braunschweig (Wolfenbüttel; Asse) and in the Lower Saxony mountain country, small-scale salinisations are often found near salt sticks. In addition, increased concentrations of chloride are located in areas of the Lower Saxony mountain region where salinar sequences (Zechstein, Upper Bunt sandstone, Middle Shell limestone, Middle Keuper, Münder-Mergel of the Oberen-Jura) occur near the surface. North of Hanover, the influence of marine claystone deposits of the lower chalk leads to an increase in the chloride content to 50-100 mg/l in the low-power quaternary deposits.《下萨克森州1:50万水文地质概览图——地下水水质：氯化物含量》 本数据集依托下萨克森州采矿、能源与地质局（LBEG）实验室数据库中的代表性氯化物浓度评估样本构建。1967年至2000年期间采集的原始数据经过两次平均化处理：针对存在多次检测记录的地下水测点，以现有检测结果的算术平均值作为其代表值；此外，对半径2000米范围内的全部采样点数值开展二次平均计算。 该数据集的分级标准兼顾了最小阈值（GFS）与德国《饮用水条例》（TVO）规定的250mg/L限值。本概览图未体现明显由点状人为输入（如垃圾填埋场、采矿排土场）导致的氯化物浓度升高情况。需注意，本图仅按深度层级展示氯化物含量，未结合当地水文地质条件。因此，若未结合具体水文地质背景（如水文地质底板结构）且未将数据用于详细勘查，则不得直接进行数值对比。 下萨克森州氯化物浓度最低的区域为哈尔茨(Harz)与措林(Solling)地区，浓度区间为5-10mg/L；吕讷堡石楠草原(Lüneburg Heath)的浓度区间为10-30mg/L。浓度超过50mg/L的区域，通常无法仅通过大气输入与蒸散发富集作用解释，一般属于地下水的地成因或人为盐化污染。 下萨克森州地下水氯化物强原生盐化区域主要分布于沿海及易北河、威悉河、埃姆斯河河口地带（海水入侵引发的海岸盐化），浓度可达15000-16000mg/L。非海水盐化区域的氯化物浓度多介于30-50mg/L之间。 地下水地成因盐化的另一成因是地下盐岩体的赋存。此类盐化的典型案例多见于河流低地（如劳恩堡附近的易北河、戈勒莱本、耶策尔河与武姆河区域），其氯化物浓度升高由盐构造的上升聚集水所致。此外，在汉诺威周边（罗恩嫩贝格、萨尔施泰特）、萨尔茨吉特、不伦瑞克（沃尔芬比特尔、阿塞矿区）以及下萨克森山地，盐柱附近常出现小规模盐化区域。同时，下萨克森山地内出露含盐岩系（蔡希斯坦统(Zechstein)、上斑砂岩、中壳灰岩、中凯珀阶、上侏罗统明德页岩）的区域，也存在氯化物浓度升高的现象。 汉诺威以北区域，下白垩统海相泥质岩沉积会使低能第四纪沉积层中的氯化物含量升高至50-100mg/L。