A Study On The Hydraulic Regulation And Control Measures And Its Influences About The Vertical Migration Of Pollutangts From The Contaminated Underground Aquifer To The Soil

At present,more than 60%of municipal solid waste（MSW）are disposed by sanitary landfill,however some landfills are only simple（non-regular）landfills.Due to the lack of regular anti-seepage measures,the imperfection of impervious system or the leakage of impervious materials,it is easy to cause landfill leachate leakage to pollute the soil of the underlying unsaturated zone and the groundwater environment.When the groundwater is contaminated,the pollutants in the water will be vertical migration upward with capillarity and then pollute the soil overlying aquifer.In order to study the effects of the pollutants solute migration in capillary bands that under the different hydraulic conditions,two typical heavy metal pollutants which cadmium and chromium ere selected as research target pollutants,and an aquifer-soil coupling simulation device is established to simulate capillary rise in the unsaturated zone soil by changing the groundwater runoff and groundwater depth.The experiment study the law of pollutants vertical migration which can provides reference for avoiding or reducing the pollution of the surrounding soil from the landfill.According to the soil adsorption test and migration test of contaminants in the aquifer,the results of the test study show that:（1）The results of adsorption kinetics test showed that when the initial concentration of cadmium and chromium both was 10mg/L,the adsorption equilibrium time of the two heavy metal pollutants was 19h and 5h respectively,and the adsorption in the soil were 98.70mg/kg and 11.92mg/kg respectively.That is,the adsorption of cadmium is larger than the adsorption of chromium,but the adsorption rate of chromium is higher.The adsorption thermodynamic test results show that the Langmuir isotherm K of cadmium and chromium is0.8108 and 0.2918 respectively,that is,the adsorption of cadmium is larger than that of chromium.（2）At three different groundwater runoffs（Q₁=20L/d,Q₂=35L/d,Q₃=50L/d）,the time of capillary water rises to the top were 5700 minutes,7200 minutes,and 8700 minutes respectively.The capillary rise height and time are consistent with the power function;with the increase of groundwater runoff,The content of pollutants at the same position showed an increasing trend,such as chromium content of S9 sample points was 0.65 mg/L,1.05 mg/L,and 1.15 mg/L,followed by cadmium content was 10.90 mg/L,11.53 mg/L,and 12.33 mg/L.Therefore,from the perspective of reducing the migration of pollutants,the groundwater runoff should be controlled and reduced as much as possible.（3）At three different groundwater depth（H₁=45cm,H₂=40cm,H₃=35cm）,the time of capillary water rises to the top were 7800 minutes,5700 minutes and 3900 minutes respectively.The capillary rise height and time are consistent with the power function;with the decrease of groundwater depth,The content of pollutants at the same position showed andecreasing trend,For example,chromium content of S8 sampling point was 0.65 mg/L,1.05 mg/L and 1.15 mg/L,and the cadmium content was 10.90 mg/L,11.53 mg/L and 12.33mg/L,respectively.Therefore,from the perspective of reducing the migration of pollutants,the groundwater runoff should be controlled and reduced as much as possible.In summary,to reduce the effect of the contaminated aquifer on the overlying soil,groundwater runoff or the groundwater depth should be reduced.In practical engineering applications,these objectives can be achieved through some measures such as covering the landfill and setting barriers.