Abstract: According to the particularity of porous structure and mineral composition in coastal energy storage shallow brackish aquifers, a controllable experiment of one-dimensional (1D) sand column infiltration was conducted. By combining with the mass transfer theory in porous media, this study probed into the internal connection at the porous scale that gave rise to the aquifer medium micro-nano particles detachment, transportation and attachment resulting from the particle morphology characteristics, and then explicated the induced mechanism of particles redistribution. The results indicate that, compared with another type of particle, the release rate of the spherical silica powder is the highest, and the accumulative weight of this particle in effluent liquid is up to 93.74 mg. However, the release rate of the brackish aquifer sand is the lowest, merely 0.62% when the hydrodynamics and physical-chemical properties of seepage solution is the same. Morover, the mechanical composition and porous structure of aquifer medium is also similar. After that, based on experimental results, the inversion of the adopted particle transport model with two kinetic retention sites is introduced. The results show that the brackish aquifer sand of the first-order attachment coefficient on the second kinetic site which is assumed to be irreversible and depth-dependent is 2 orders of magnitude higher than another two groups of the artificial aqueous medium column. Combined with experimental results from the SEM and the Zeta potential of particles, it is found that the seepage shear stress is directly proportional to the normal cross-sectional areas of particle. The diffuse electric double layer repulsion is obvious different from the change of particles morphology and mineral composition, which are based on the analysis of forces and force torque balance for the particles located on the internal grain surface of the aquifer medium. Therefore, the spherical silica powders usually detach in the form of monomer type from the grain surface of the porous media. However, regarding flake secondary clay mineral particles, the regular release type is a large size particle group which could enhance the probability of the attachment in matrix surface or the captured by the pore throat.

Key words: brackish aquifer, micro-nano particles, morphology characteristics, transportation, sand column experiment