The Impacts of Environmental Conditions on the Applicability of Selected Groundwater Tracers; A Laboratory Research

In this research, the effects of a number of environmental factors such as pH, sunlight, temperature, salinity, free chlorine, and adsorption in porous media are evaluated on the applicability of selected groundwater tracers. Tracers from different categories as fluorescent dye tracers (uranine, eosin and rhodamine-B), chemical salts (NaCl and KCl), and non fluorescent dye tracer (KMnO4) have been tested in the laboratory. The results showed that uranine losses its florescence in acid environments, while in alkaline conditions its florescence increases. The results also showed that due to photochemical decay, if subjected to sunlight, eosin is the most unstable tracer. KMnO4 turns to brown under sunlight and high temperature conditions and may lose its usefulness as a tracer. Results also confirmed that the fluorescence intensity of rhodamine-B decreases as temperature and/or salinity increases. Uranine and eosin showed high resistance against high temperature and high salinity conditions. An important factor in groundwater tracing is adsorption of tracer in porous media environment. Our research showed that rhodamine-B would easily be adsorbed to fine grain porous media while uranine and eosin high resist against adsorption. KMnO4 is also easily adsorbed. Chlorine used in drinking water treatment is strongly oxidizing even in low concentrations and can lead to the elimination of fluorescence of uranine, eosin and rhodamine-B.