Master thesis

Dong Liu (2015)
Überblick zum Einsatz von Tracersubstanzen in der umweltwissenschaftlichen Prozessforschung. Master thesis, Technische Universität Dresden, December 2015

Abstract

Fluorescent dye tracers Uranine and Eosine Y as well as non-fluorescent dye Brilliant Blue FCF are used to characterize water flow and transport of organic substances in the saturated and unsaturated soil zone. For correct interpretation of tracer tests, the behaviour of used compounds under various experimental conditions must be well understood. Photodecomposition rates of dye tracers and the influence of pH and sorptive capacities of three soils (loamy and silty sands) on the behaviour of dye tracers were investigated in static and equilibration experiments. The highest photodecomposition rate was observed for Eosine Y (complete degradation after ca. 100 minutes) followed by Uranine (ca. 200 minutes) and Brilliant Blue FCF (ca. 300 minutes) in concentrations of 10 mg/l, 8 mg/l and 12 mg/l, respectively. A change in fluorescence intensity could be determined for Uranine and Eosine Y at pH values lower than 6. All dye tracers studied exhibited a very fast sorptive kinetic (few minutes), with the highest adsorption coefficients observed for Brilliant Blue FCF, followed by Uranine and Eosine. For Uranine and Eosine it cannot be easily distinguished between real sorption and reduction in fluorescence intensity at lower pH values. The persistence of dye tracers in the soil matrix was estimated in desorption experiments: the amplitude of adsorption-desorption hysteresis decreased from Brilliant Blue FCF, which exhibited the highest desorption, to Uranine, with minor hysteresis, and Eosine Y, with no hysteresis at all.