Study On Vertical Migration And Mechanism Of Solute To Soil In Polluted Groundwater

Groundwater and soil pollution around landfills have gradually emerged and received widespread attention.However,a large number of related researches are mainly concentrated in the landfill and surrounding direct influence areas,ignoring the phenomenon that pollutants in the water will migrate upwards due to capillary action and then contaminate the soil overlying the aquifer.In response to the above problems,a soil-aquifer coupling test device was constructed to simulate the vertical migration of solute into soil in contaminated groundwater,and to study the law of vertical migration of contaminants from the aquifer to the soil,and based on this,for different solute The preliminary exploration of the migration mechanism provides a useful reference for the study of the effect of contaminated groundwater on soil and prevention and control.Adsorption test results show that the time for Cd to reach equilibrium is significantly longer than the time for Cr to reach equilibrium,the former being 960 min and the latter being 300 min.When the concentration of solute in the solution was both 10 mg/L,the concentration of Cd and Cr in the soil reached 98.70 mg/kg and 11.91 mg/kg respectively when the adsorption reached equilibrium,indicating that the adsorption of Cd on the soil was stronger than that of Cr.The height of soil capillary rise and rise time are power functions.The position height is linearly related to the soil moisture content.The water content is 30.15%~35.13% at a height of 2cm from the aquifer and 25 cm from the aquifer.The moisture content in soil decreased to 23.12%~26.81%.Cr concentration in soil increased with the extension of test time and decreased with the increase of capillary rise height.The concentration was 6.319~27.766mg/L when the height was 2cm away from the aquifer.The concentration was 0.419~2.742mg/L at a height of 25 cm from the aquifer.The change trends of Cd,ammonia nitrogen and Cr were similar.The content of the two was 46.174~69.982mg/L and 1.415~3.623 mg when they were 2cm away from the aquifer./L,0 to 45.494 mg/L and 0.168 to 0.905 mg/L,respectively,25 cm away from the aquifer.By analyzing the migration curves of three different solutes in the soil,the migration rule of heavy metal Cr and heavy metal Cd is roughly the same,but when Cr migrates in the soil,there will be a small amount of Cr ions migrated upwards quickly with capillary water.The Cr ion is still enriched in the position where the bottom of the soil is in contact with the aquifer and migrates slowly upwards over time.During the migration of Cd ions,there will not be a small amount of ions that migrate from the bottom of the soil to the capillary water.The transfer of ammonia nitrogen is restricted by the moisture content.When the initial soil moisture content does not reach saturation,the moisture content and the ammonia nitrogen concentration show a linear relationship.When the soil moisture content reaches saturation,the ammonia nitrogen will saturate the soil moisture content.The part of the enrichment began,and in this part of the soil,the concentration of ammonia-nitrogen gradually increased,while in the soil where the water content did not reach saturation,the ammonia nitrogen and water content still showed a linear relationship.