Abstract

This study presents a new method for deriving the breakthrough curve (BTC) of Br tracer by measurements in the laboratory. In this method, the breakthrough is recorded by an ion selective electrode placed in a flow cell into which a peristaltic pump redirects part of the effluent. Special care was taken to make the measurements insensitive to variations in ionic strength in the effluent by mixing in the ionic strength adjuster. To evaluate this newly proposed method, BTCs of Br and 2H were measured for two saturated columns during steady-state flow under ponding boundary conditions. A concentration pulse was generated by the newly developed infiltration head with two independent sets of injection capillaries, which dosed water or tracer solution into the ponding water while keeping the ponding height constant. In addition to the continuous automatic method, discrete samples of effluent were analyzed for Br by ion chromatography and for 2H using laser spectroscopy. Experiments were conducted on packed sand and on an undisturbed sample of coarse sandy loam soil. In both cases, the results showed good agreement between BTCs of Br and 2H measured using the proposed method and those derived using traditional methods on effluent samples collected during the same experiment. Additional experiments showed good reproducibility of the BTC measurement during replicated experiments.

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