Particles Release on a Sea-Freshwater Interface by Flow Velocity and Rate of Salinity Decrease Effects

Adopting horizontal column experiments, taking the aquifers sample containing minim clay mineral (mainly illite) in Dagu River aquifer, this paper studies the influences of flow velocity and ionic strength on particles release, as well as the relationship of between them. Through the DLVO theory calculation and the column experiments, the Critical Salt Concentration (CSC) of the Dagu River aquifer is determined as 0.05 mol/L approximately. For the constant velocity, the slower the rate of salinity decrease, the higher the peak of particles concentration is. However, the total amount of colloid particles is almost constant at different rates of salinity decrease. For constant rate of salinity decrease, the peak of particles concentration decreased as velocity increased, but the total amount of particles released rose up. Meanwhile, the experiments also indicated the existence of critical velocity, and revealed that the critical velocity dropped with the increase of salt concentration. When the concentration of NaCl solution decreased from 0.17 mol/L to 0.06 mol/L, the critical velocity decreased from 3 cm/min to 2.5 cm/min, which is consistent to the results predicted by DLVO theory.