Experimental And Simulation Study On Adsorption And Migration Of Heavy Metal Cadmium In Shallow Strata Of Shanghai

Shanghai is a highly industrialized city,is the country's economic and financial center.The rapid development of industrialization in the past few decades,Shanghai's economic development has made gratifying achievements,at the same time,Shanghai is also facing the serious problem of soil heavy metal pollution.However,the current study of heavy metal pollution in soil in Shanghai area to stay at the surface of the dust layer or roadside tillage,and on the diffusion of heavy metal pollution in different strata in the Shanghai area of different types of undisturbed soil in law blank.Therefore,this article from the perspective of geology,Shanghai shallow silty clay and silty sand as the research object,using cadmium as an example,using the indoor soil column simulation experiment and quantitative chemical analysis methods,adsorption and diffusion of heavy metal cadmium ion in Shanghai shallow clay soil and sand soil the brief analysis of its internal mechanism,and use the Geostudio software to simulate the migration test of cadmium in silty clay,the main conclusions are as follows:(1)In Shanghai,this kind of low permeability silty clay has little effect on the solute migration,and the migration of heavy metals mainly depends on hydrodynamic dispersion and molecular diffusion.The migration and migration of heavy metals in the low permeability soil are not synchronous,and the relationship between them is very small.In the experiment,the results are very similar.(2)The migration of heavy metal cadmium in silty clay is based on the step by step descending mode.At the same time,there will be an equal or similar stage in the depth of one or more segments.Due to the adsorption of clay and retention of mechanical barrier function,diffusion cannot smooth freely soon the migration of heavy metal pollution in soil,but difference in concentration under the action of a little bit to the molecular diffusion migration down from top to bottom,from dense and sparse showing the concentration gradient of different concentration gradient,change trend also the magnitude of the decline in.(3)The migration of heavy metal cadmium in the strong alkaline sandy soil is not as obvious as the molecular diffusion and desorption in the cohesive soil.The migration of cadmium is dominated by the strong chemical adsorption and retention of soil,and the convective migration of water is weak due to the strong adsorption of strong alkaline sand.In the migration test of silty sand,the solute 99% was in the surface,a small amount of water reached the depth of 1-3 cm,it is obvious that the influence of water seepage on the migration of heavy metal Cd in the alkaline sandy soil of Shanghai is not significant.(4)Through the adsorption and penetration test of cadmium in silty sand,it is found that the adsorption saturation value of cadmium in strong alkaline sandy soil in Shanghai area is about 2566mg/kg.The saturation value of soil adsorption to ions reflects the ability of soil to adsorb ions,and the soil pH is an important factor affecting the adsorption saturation value.Silt adsorption capacity of heavy metal cadmium and the unit mass contact quality solute negative exponential function,with the increase of solute quality per unit mass of the contact,the quality of powder sand adsorption solute units will also increase,the increase rate decreases,the rate increase until zero adsorption reached saturation.(5)The application of Geostudio on clay column Migration Experiment and numerical simulation,the steady flow,the convection dispersion and particle tracking analysis,the results obtained are consistent with the seepage pollutant migration distance and test results were confirmed using Geostudio software to simulate the feasibility of predicting soil contaminant migration.(6)At the venue before the survey,should fully collect the original emission site use types,the types of pollutants,the use of the site may be limited,pollutant discharge pipe arrangement and way,the discharge of pollutants and other information,convenient in detailed investigation before better analysis,simulation and prediction,reduce the workload of the blind.