Abstract:

Kast pools often lead to a trailing of breakthrough curve (BTC) in karst conduits. It is of great significance to study the influence of the pool on its breakthrough curve for predicting and controlling groundwater pollution. Different sizes and number of pools were designed and the indoor tracer experiments were performed to investigate the influence of the pool volume on its breakthrough curve. The experimental results showed that as the pool volume (pool size or pool number) increased, the BTC tailing increased and the peak mass concentration decreased; As the flow rate increased, the BTC trailing decreased and the peak mass concentration of both symmetrical and asymmetric pools increased first and then decreased. The penetration time of main solute plume in the symmetrical pool was basically constant with the increase of pool size, and increased exponentially with the number of pools. The other time characteristic parameters basically increased linearly with the pool volume, and the adjusted peak mass concentration showed a power function relationship with the pool volume. When the pool volume was the same, the time variance, the penetration time of the descending solute plume, and the tracer duration time for different pool sizes were larger than for different number of pools, while the mean migration time was basically the same for the two pool distributions. The penetration time of the main solute plume and the adjusted peak mass concentration in the asymmetric pool were basically the same for the two pool distributions. The mean migration time basically increased linearly with the pool volume in the symmetric and asymmetric pools, the penetration time of the main solute plume and the adjusted peak mass concentration respectively showed a good linear and power function relationship with the volume of the asymmetric pool. It is indicative to predict the volume of pools in karst conduits by using these three characteristic parameters of the breakthrough curve in the field.

Key words: pool volume')">

pool volume, breakthrough curves, characteristic parameters, tracer experiments