Institute of Applied Geosciences, Division of Hydrogeology, Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, 76131, Karlsruhe, Germany.
Ground Water. 2021 Jan;59(1):59-70. doi: 10.1111/gwat.13015. Epub 2020 May 27.
The monitoring of water quality, especially of karst springs, requires methods for rapidly estimating and quantifying parameters that indicate contamination. In the last few years, fluorescence-based measurements of tryptophan and humic acid have become a promising tool to assess water quality in near real-time. In this study, we conducted comparative tracer tests in a karst experimental site to investigate the transport properties and behavior of tryptophan and humic acid in a natural karst aquifer. These two tracers were compared with the conservative tracer uranine. Fluorescence measurements were conducted with an online field fluorometer and in the laboratory. The obtained breakthrough curves (BTCs) and the modeling results demonstrate that (1) the online field fluorometer is suitable for real-time fluorescence measurements of all three tracers; (2) the transport parameters obtained for uranine, tryptophan, and humic acid are comparable in the fast flow areas of the karst system; (3) the transport velocities of humic acid are slower and the resulting residence times are accordingly higher, compared to uranine and tryptophan, in the slower and longer flow paths; (4) the obtained BTCs reveal additional information about the investigated karst system. As a conclusion, the experiments show that the transport properties of tryptophan are similar to those of uranine while humic acid is partly transported slower and with retardation. These findings allow a better and quantitative interpretation of the results when these substances are used as natural fecal and contamination indicators.
水质监测，特别是岩溶泉的监测，需要快速估计和量化指示污染的参数的方法。在过去的几年中，基于荧光的色氨酸和腐殖酸测量已成为实时评估水质的有前途的工具。在这项研究中，我们在岩溶实验场进行了对比示踪试验，以研究色氨酸和腐殖酸在天然岩溶含水层中的运移特性和行为。将这两种示踪剂与保守示踪剂尿囊素进行了比较。荧光测量是在野外在线荧光计和实验室中进行的。获得的穿透曲线（BTC）和建模结果表明：（1）在线野外荧光计适用于所有三种示踪剂的实时荧光测量；（2）在岩溶系统的快速流动区，获得的尿囊素、色氨酸和腐殖酸的输运参数具有可比性；（3）与尿囊素和色氨酸相比，腐殖酸的运移速度较慢，在较慢和较长的流动路径中，相应的停留时间也较高；（4）获得的 BTC 揭示了有关研究岩溶系统的其他信息。总之，实验表明，色氨酸的输运特性与尿囊素相似，而腐殖酸则部分输运速度较慢且有滞后。当这些物质被用作天然粪便和污染指示物时，这些发现可以更好地对结果进行定量解释。
