Dyeing experiment (hydrogeology)
A coloring experiment in hydrogeology is the targeted introduction of a chemical substance for the purpose of determining the course of an underground drainage. With a sufficiently dense arrangement of the infiltration points, the catchment area of a source or the position of the watershed can be determined. Subterranean drainage is an essential feature of karst areas , so that color attempts are often counted among the methods of speleology .
Coloring experiments are called dye tracing in English ; this term is also used synonymously in the German specialist literature. The substance introduced is called a tracer .
Originally, actual dyes were used as tracers , the appearance of which can be visually perceived at a source. Nowadays, however, invisible substances are often used and detected chemically. These often cheaper agents are harmless and imperceptible to humans; their occurrence can be detected fully automatically with electronic sensors. Nevertheless, one still speaks of the dyeing attempt, even if no actual dyeing takes place.
When using salts one also speaks of salting attempts .
history
In 1877 the geologist Adolf Knop from the Technical University of Karlsruhe demonstrated by means of a dye test (uranine) that the water from the Danube sinking feeds the Aachtopf .
An involuntary dyeing attempt took place in 1901, when a fire on the premises of the Pernod company in Pontarlier in the French Jura threatened to spread to the absinthe warehouse. To avoid the alcohol catching on fire and the associated risk of explosion, an employee opened the barrels, whereupon a million liters of the high-proof absinthe flowed into the Doubs , the water of which became milky as a result of the louche effect and gave off the typical aniseed smell. Two days later the same milky water leaked from the Loue spring, 15 kilometers away . Thus the Doubs have the riverbed swallow holes are present which derive a portion of the river water and underground feed the Louequelle.
Nine years later, the speleologist Édouard Alfred Martel repeated the experiment by injecting a fluorescent dye into a swallow hole in the bed of the Doubs. After 64 hours the dye reached the source of the Loue.
method
In order to determine the path of the water, the experiment must be planned precisely. A suitable tracer is selected and all possible re- exit points are equipped with appropriate measuring devices. Then a larger amount of water is released with the diluted tracer at the infiltration point and the measuring points are monitored. The measurement duration can be very different, but is typically less than a week. Several individual measurements are combined into series of measurements in order to be able to determine not only the flow paths and flow velocities but also the qualitative and quantitative pathways for pollutants. For this purpose, the bed must also be measured.
It makes sense to use substances that do not occur in nature, at least not in the study area. In principle, they must be harmless, be spread well with the groundwater flow and be quantitatively detectable even in the case of strong dilution.
The following substances are used as tracers:
- Fluorescent dyes: uranine , eosin , rhodamine
- Easily detectable salts: sodium bromide , sodium chloride , potassium salt , borax
- Radionuclides : 3H, 51Cr
- Special drift bodies : bear moss spores , fluorescent plastic particles
The necessary permits are also an important part of the planning. Karst areas are usually groundwater protection areas , so all such experiments must be registered and / or approved. Contact persons are the affected communities and the nature conservation authorities.
literature
- Werner Käß : Geohydrological marking technology. (= Textbook of Hydrogeology. Volume 9). Borntraeger brothers, Berlin / Stuttgart 1992, ISBN 3-443-01013-X .
credentials
- ↑ Karst Geology: karst spring
- ↑ Karst Features of France: The Pernod Accident (English)
- ↑ Tracer attempt / staining attempt ( Memento of the original from February 7, 2005 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , As of May 27, 2008
