The rare earth element (REE) group is widely used for geochemical prospection and the hydrochemical differentiation of waters. Most of the currently applied methods use normalized REE patterns to determine enrichments or depletions of certain REE in comparison to standard materials, which are caused by specific environmental conditions. Contrast agents containing Gadolinium (Gd), which are used for magnetic resonance imaging (MRI), have been emitted into surface waters since the 1980s. Patients excrete these contrast agents shortly after ambulant medication in hospitals or at home. Sewage treatment is currently unable to hold back Gd from this anthropogenic source. Therefore, the Gd concentration in the receiving channel increases significantly and creates a Gd peak in the REE pattern. This anthropogenic peak propagates into adjacent groundwater bodies. In a karst aquifer showing a connection between a river/ponor (input) and three springs (output), such an anthropogenic Gd anomaly has been traced, the local Gd background quantified, and surface water groundwater interaction evaluated. In two sampling campaigns, water samples were taken every day at the input and output side during one week in February and three weeks in May. Sampling of springs and brooks in the vicinity of the karst aquifer proved excessive Gd from anthropogenic sources. The evaluation of concentration, mass flow and total mass of Gd show that Gd can be an environmental tracer to monitor surface water-groundwater interaction as well as the anthropogenic influence on water bodies. Further anthropogenic pollutants - diclofenac, carbamazepine, galaxolide, caffeine, and acesulfame-K - representing different classes of common organic substances were tested as co-indicators to Gd. However, out of these only acesulfame-K was detected and is related with the Gd-anomaly. Our results indicate that Gd is a more powerful indicator of surface water- groundwater interaction than most organic pollutants.

稀土元素（REE）组广泛用于地球化学勘探和水域的水化学区分。当前使用的大多数方法都使用归一化REE模式来确定某些REE与标准材料相比的富集或消耗，这是由特定环境条件引起的。自1980年代以来，用于磁共振成像（MRI）的含Ga造影剂（Gd）已排放到地表水中。病人在医院或家中用药后不久便排泄这些造影剂。目前，污水处理无法抑制这种人为来源的Gd。因此，接收通道中的Gd浓度显着增加，并在REE模式中产生Gd峰值。这个人为高峰传播到相邻的地下水体。在一个喀斯特含水层中，显示出一条河流/施主（输入）和三个泉水（输出）之间的联系，这种人为的Gd异常已经被追踪，局部的Gd背景被量化了，地表水与地下水的相互作用也得到了评估。在两次采样活动中，在2月的一个星期和5月的三个星期，每天在输入和输出端进行水采样。岩溶含水层附近的泉水和溪流的采样证明来自人为来源的Gd过多。对G的浓度，质量流量和总质量的评估表明，G可以作为环境示踪剂来监测地表水与地下水的相互作用以及人为因素对水体的影响。其他人为污染物-双氯芬酸，卡马西平，galaxolide，咖啡因和乙酰磺胺酸钾（代表不同类别的常见有机物质）已作为Gd的辅助指标进行了测试。但是，在这些中仅检测到乙酰磺胺酸钾，并且与Gd异常有关。我们的结果表明，Gd比大多数有机污染物更能反映地表水与地下水的相互作用。