Complex model of interaction between seawater and underground brine in muddy tidal flat
In the world,many coastal underground brine resources are distributed in the muddy tidal flat area,but the research on the subterranean estuary in this area is only in the primary stage,and the model has not been established.In this paper,the southern bank of Laizhou bay was selected as a typi-cal study area.Electrical resistivity tomography monitoring,pore water conductivity monitoring,sea-water and groundwater conductivity measurement were carried out in the areas with different vertical permeability coefficients of surface sediments.The sediment-physical relationship of muddy tidal flat was clarified.A standard for the division of seawater-groundwater mixed zones was established.This standard combined with the electrical resistivity tomography monitoring results at each tidal time to an-alyze the complex exchange mode of seawater-groundwater and its influencing factors,and to reveal the temporal and spatial distribution of the mixing zone.The research results showed that the biological chan-nels clustered in the silt layer were the main ways of seawater-groundwater exchange during the tidal cycles.The formation mechanism of"upper saline plume"and"groundwater discharge tunnel"in the muddy tidal flat subterranean estuary and the seawater-groundwater exchange process were different from those of sandy tidal flats.Decreasing the permeability of tidal flat sediments would cause the direct exchange rate of seawater-groundwater through sediments to decrease,leading the main exchange path to shift to high-permeability chan-nels.The flow rate of intrusion and excretion in the channels would increase.
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