The packed bed column (H = 2m) is filled with alternate soil (coarse) and sand samples. I want to study the residence time of my target compound but before that I require a tracer to monitor the flow for calculating the HRT. What are the suitable tracers available that are cost effective as well as inert (should not interact and adsorb on soil and sand)?
Dear Kshitiz,
The anion bromide is a relatively low cost tracer that is often used to determine conservative (no interaction) transport parameters in sand. Sodium bromide salt can be used to make the tracer solution. Alternatively, you might want determine breakthrough visually after infiltrating water with any type of colourant added. This would be even more cost-effective, but would prohibit determination of dispersion factors. Hope this helps.
Best regards,
Niels
Thanks Niels. But how we can measure the bromide conc. and does it will work with packed soil also?? I have a doubt that will the anion be adsorbed on sand and soil because the height of packing is around 2 metres.
Hello Kshitiz,
Bromide would typically be measured using an ion chromatograph (IC). It would work with a saturated or unsaturated packed soil, as long your able to collect water samples at the bottom of the column. Since the bromide is negatively charged it would normally not suffer from adsorption to sands and soils that are typically positively charged as long conditions are not acidic. Assuming you have homogeneous soil conditions, the size of the column would be expected to relate linearly to your measured residence time.
Good luck,
Niels
There are also specific ion electrodes (like a pH meter) for bromide, and the salinity contrast of the tracer solution may be monitored in the effluent of the column also using an electrical conductivity electrode.
Bromide has the potential (in some soils) to be somewhat reactive in that it is charged and may not be able to transport through some pore spaces due to the repulsion from soil surface charge (i.e., anion exclusion). So, you might consider other nonreactive tracers including stable isotopes of water and pentafluorobenzoic acid (PFBA).
PFBA can be dissolved in water, injected as a tracer, and analyzed using UV spectroscopy (254 nm wavelength). Hope this helps.
Well,
Environmental isotopes like Tritium can be used as a suitable tracer for tracking water flow.
Regards
What can we use as a non-reactive tracer for soil ground water for monitoring different reactions like denitrification?
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