Hydrogeology Department, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany.
Environ Monit Assess. 2021 Feb 5;193(3):112. doi: 10.1007/s10661-021-08880-y.
The mainly agricultural input of NO and compliance with drinking water guideline values pose major challenges for many water suppliers. Additionally, associated changes in hydrochemistry, especially concerning products of NO reduction (Fe, Mn, Ca, Mg, SO, HCO) and subsequent reactions, can have a major influence on mineral saturation states and well yield: well productivity can be strongly reduced by mineral precipitation and silting. To evaluate hydrogeochemical evolution and clogging potential for a given well field, thorough hydrochemical and geochemical investigations are required. Therefore, time-dependent and depth-specific ion concentrations in water samples (n = 818) were analysed in a catchment area of a waterworks in western Germany. The sediments of the aquifers were extensively investigated for their geochemistry (CS, scanning electron microscope, aqua regia digestion and dithionite solution; n = 253). In addition, PhreeqC was used to model saturation indices in order to identify possible mineral precipitation in the wells. Results show a high NO input into deep wells screened in Tertiary sediments due to an admixture of Quaternary groundwater. Directly at the Quaternary-Tertiary boundary, chemolithotrophic NO reduction consuming pyrite occurs. Protons released during the process are pH-buffered by dissolving carbonate minerals. Overall, the hydrochemistry and especially the saturation indices are strongly influenced by NO reduction and its degradation products. A change in well yield has not yet been observed, but future clogging by ochre formation or sintering cannot be excluded.
主要的农业输入物氮和符合饮用水指导值为许多水供应商带来了重大挑战。此外，水化学的相关变化，特别是与氮还原产物（铁、锰、钙、镁、硫、碳酸氢根）及其后续反应有关的变化，会对矿物饱和度状态和水井出水量产生重大影响：矿物沉淀和淤积会强烈降低水井的产能。为了评估特定水井场的水文地球化学演化和堵塞潜力，需要进行彻底的水文化学和地球化学调查。因此，对德国西部一个水厂集水区的 818 个水样进行了时间依赖和深度特定的离子浓度分析。含水层的沉积物进行了广泛的地球化学研究（CS、扫描电子显微镜、王水消解和连二亚硫酸钠溶液；n = 253）。此外，还使用 PhreeqC 来模拟饱和度指数，以确定水井中可能的矿物沉淀。结果表明，由于第四纪地下水的混合，第三纪沉积物中的深井中输入了大量的氮。在第四纪和第三纪的交界处，直接发生消耗黄铁矿的化学生态学氮还原。该过程中释放的质子通过溶解碳酸盐矿物来缓冲 pH 值。总的来说，水化学，特别是饱和度指数，受到氮还原及其降解产物的强烈影响。目前尚未观察到水井出水量的变化，但未来仍不能排除因铁矾形成或烧结而堵塞的可能性。
