Groundwater pollution threatens human and ecosystem health in many regions around the globe. Fast flow to the groundwater through focused recharge is known to transmit short-lived pollutants into carbonate aquifers, endangering the quality of groundwaters where one quarter of the world’s population lives. However, the large-scale impact of such focused recharge on groundwater quality remains poorly understood. Here, we apply a continental-scale model to quantify the risk of groundwater contamination by degradable pollutants through focused recharge in the carbonate rock regions of Europe, North Africa, and the Middle East. We show that focused recharge is the primary reason for widespread rapid transport of contaminants to the groundwater. Where it occurs, the concentration of pollutants in groundwater recharge that have not yet degraded increases from <1% to around 20 to 50% of their concentrations during infiltration. Assuming realistic application rates, our simulations show that degradable pollutants like glyphosate can exceed their permissible concentrations by 3 to 19 times when reaching the groundwater. Our results are supported by independent estimates of young water fractions at 78 carbonate rock springs over Europe and a dataset of observed glyphosate concentrations in the groundwater. They imply that in times of continuing and increasing industrial and agricultural productivity, focused recharge may result in an underestimated and widespread risk to usable groundwater volumes.

地下水污染威胁着全球许多地区的人类和生态系统健康。众所周知，通过集中补给快速流入地下水会将短期污染物传输到碳酸盐含水层中，从而危及世界四分之一人口居住的地下水质量。然而，这种集中补给对地下水质量的大规模影响仍然知之甚少。在这里，我们应用大陆尺度模型来量化欧洲、北非和中东碳酸盐岩地区集中补给可降解污染物造成地下水污染的风险。我们表明，集中补给是污染物广泛快速迁移到地下水的主要原因。如果发生这种情况，地下水补给中尚未降解的污染物浓度会从渗透过程中浓度的 <1% 增加到约 20% 至 50%。假设实际的施用率，我们的模拟显示，草甘膦等可降解污染物在到达地下水时可能会超出其允许浓度 3 至 19 倍。我们的结果得到了对欧洲 78 个碳酸盐岩泉的年轻水成分的独立估计以及观察到的地下水中草甘膦浓度的数据集的支持。它们意味着，在工业和农​​业生产力持续和提高的时期，集中补给可能会导致可用地下水量被低估和普遍存在的风险。