Pore-volume changes in porous media during water–rock interaction can be studied using hydrological tracers. The tracers used here were amino G acid, napthionic acid and fluorescein at pH 3 and 6.5 in contact with basaltic glass, quartz and rhyolite. The experimental setup mimicked that of a hydrological tracer test where a fixed volume of tracer was injected into a flow-through column and the breakthrough curve monitored. The measured breakthrough tracer curves were compared to theoretical 1-D reactive transport simulations calculated using the PHREEQC program. In some cases the tracers were observed to behave ideally, whereas in others they clearly reacted with the solid surfaces. This implies that some common hydrological tracers used in groundwater hydrology may not be suitable under all conditions as they may react with the surrounding rocks in the groundwater system.
