| In recent years, the problem of soil pollution has become more and more prominent, especially the heavy metal pollution. Soil heavy metal pollutants can enter into the soil through a variety of ways, some of them are absorbed by the soil, the other part is constantly moving downward, and may enter into the gro-undwater to pollute the groundwater. At the same time, the contaminated top so-il.enters into human and animal bodies through the food chain, threatening their h-ealth and survival. Adding a certain proportion of passivator has been developed to repair and treat the soil polluted by heavy metals. Therefore, it is of great t-heoretical and practical significance to study the adsorption, accumulation, migra-tion and prediction of heavy metal pollutants in natural soil and soil with a certain proportion of passivator.In this paper,the 0-20 cm topsoil of the farmland near the Mawei River Basin in Xiaoquan town of Deyang City was studied.The heavy metal Cd with serious pollution was selected as the research object.Through static adsorption and dynamic soil column leaching experiments,the accumulation and migration of Cd in the natural soil and the soil with a certain proportion of passivator were analyzed,and the migration of Cd in the soil was simulated by hydros-1d model Fitting and forecasting.The main results are as follows:（1）Through the static adsorption experiment,the pseudo second order adsorption kinetic equation was determined to fit the kinetic process of Cd2+adsorption in four kinds of soil media,and the adsorption process conformed to the Langmuir equation.（2）The parameters needed for prediction were obtained by isothermal fitting of static adsorption experiment;At the same time,the effects of oscillation time,initial concentration and temperature on the adsorption of Cd2+were discussed.（3）According to the penetration experiment of tracer ions,the migration parameters needed for the simulation were obtained and fitted by the least square method;According to the penetration experiment of Cd2+,the basic migration law of Cd2+was obtained.（4）According to the hydrodynamic parameters calculated by HYDRUS-1D software and the migration parameters obtained from the experiment,the penetration experiment of Cd2+was simulated.The fitting values were compared with the measured values,and the R2of four soil media were all greater than 0.9,which means that all kinds of parameters are suitable for simulating the migration of heavy metal Cd in this area.（5）Taking all kinds of parameters into HYDRUS-1D,the concentration changes and vertical migration of the original soil and the soil with three kinds of passivators were predicted after continuous irrigation with sewage containing heavy metal Cd for5,10 and 20 years.This study area can provide targeted help for environmental monitoring and pollution control,agricultural production safety in Deyang City,and provide scientific basis for land management departments such as land resource utilization to formulate relevant policies. |
