Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, the University of Dublin, Ireland.
Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, the University of Dublin, Ireland.
Environ Pollut. 2024 May 15;349:123942. doi: 10.1016/j.envpol.2024.123942. Epub 2024 Apr 9.
Bacterial contamination of karst groundwater is a major concern for public health. Artificial tracing studies are crucial for establishing links between locations where pollutants can rapidly reach the aquifer systems and subsequent receptors, as well as for enhanced understanding of pollutant transport. However, widely used solute artificial tracers do not always move through the subsurface in the same manner as particles and microorganisms, hence may not be ideal proxies for predicting movement of bacterial contaminants. This study evaluates whether a historically used microbial tracer (yeast) which is readily available, inexpensive, and environmentally friendly, but usually overlooked in modern karst hydrogeological studies due to challenges associated with its detection and quantification in the past, can reemerge as a valuable tracer using the latest technology for its detection. Two field-based studies on separate karst systems were carried out during low-flow conditions using a portable particle counter along with flow cytometry measurements to monitor the recovery of the yeast at the springs. Soluble fluorescent dyes were also injected simultaneously with the yeast for comparison of transport dynamics. On one tracer test, through a karst conduit of much higher velocities, the injected yeast and fluorescent dye arrived at the same time at the spring, in comparison to the tracer test on a conduit system with lower groundwater velocities in which the yeast particles were detected before the dye at the sampling site. Both a portable particle counter and flow cytometry successfully detected yeast during both tests, thereby demonstrating the applicability of this tracer with contemporary instrumentation. Even though no significant advantages of flow cytometry over the portable counter system can be reported on the basis of the presented results, this study has shown that flow cytometry can be successfully used to detect and quantify introduced microbial tracers in karst environments with extremely high precision.
岩溶地下水的细菌污染是公共卫生的主要关注点。人工示踪研究对于建立污染物能够迅速到达含水层系统和后续受体的地点之间的联系至关重要，同时也有助于更好地了解污染物的迁移。然而，广泛使用的溶质示踪剂并不总是像颗粒和微生物一样在地下环境中移动，因此它们可能不是预测细菌污染物迁移的理想替代物。本研究评估了一种历史上使用的微生物示踪剂（酵母）是否可以重新成为一种有价值的示踪剂，该示踪剂易于获取、成本低廉且对环境友好，但由于过去在检测和定量方面存在挑战，在现代岩溶水文地质研究中通常被忽视。本研究使用便携式粒子计数器和流式细胞术测量来监测酵母在泉水处的回收情况，同时进行了两项基于现场的、针对不同岩溶系统的研究，均在低流量条件下进行。研究还同时注入了可溶性荧光染料，以比较示踪剂的迁移动态。在一次示踪剂测试中，通过流速更高的岩溶管道，注入的酵母和荧光染料同时到达泉水，而在流速较低的管道系统的示踪剂测试中，酵母颗粒先于染料到达采样点。两种测试中，便携式粒子计数器和流式细胞术都成功地检测到了酵母，从而证明了该示踪剂在现代仪器设备下的适用性。尽管根据目前的结果，无法报告流式细胞术相对于便携式计数器系统的显著优势，但本研究表明，流式细胞术可以成功地用于检测和定量岩溶环境中引入的微生物示踪剂，且具有极高的精度。
