A review of colloid transport behaviors based on coastal groundwater interaction

Based on the typical properties of coastal aquifer along with characteristics of groundwater interaction, multiphase reactive transport incorporating colloidal behaviors are presented. Specifically, this paper clarifies the mechanism of colloid behaviors driven by seawater-freshwater displacement from the macroscopic and microscopic perspectives. The findings suggest that the colloid is the link of mass transfer between terrestrial and oceanic facies. Hydrochemical variation in groundwater influence colloid transport behaviors, which are controlled by a combined effect of multiple factors. Such factors include colloid type and quantity, surface potential, groundwater pH, and ionic strength, with uncertainties of size exclusion and structural aggregation during transport. The future challenge lies within the co-transport of colloid and pollutant in the multiphase system from microscopic dimension to field scale, within which the colloid population effect during the displacement together with the aquifer sensitivity to hydrodynamic and hydrochemical conditions being the key factors. Finally, in this review, the useful foundation is put forward for long-term pollution control and resource reuse in coastal areas.