Study on the release of heavy metals from soil by simulated rainfall leaching
To investigate the release pattern of heavy metals from soils under rainfall drenching conditions in acid deposition areas,a typical suburban Guilin vegetable soil was selected for a simulated rainfall drenching soil column experiment to explore the effects of simulated rainfall with different pH(4,5,6,7 and 8)on heavy metal migration.The experimental results showed that the total dissolved solids(TDS)of the test soils showed increasing changes as the pH of simulated rainfall decreased.TDS decreased rapidly and then slowly with the increase of drenching time,while the pH of drenching solution increased rapidly and then slowly.The pH of the leachate was negatively correlated with TDS and positively correlated with the cumulative leaching of heavy metals.It was also found that different heavy metals showed different leaching patterns when the simulated rainfall was applied to the test soils.Zn and Cd leaching was divided into two stages of rapid release and relatively slow release,Pb was divided into rapid release and stable release stages,and Cu,Hg,As and Sb leaching was generally in a period of uniform growth.The kinetic model of heavy metal release from soil under rainfall leaching conditions was developed by fitting the first-order kinetic equation,Elovich equation,double constant equation and parabolic diffusion equation.The fitting revealed that the release process of heavy metals was not suitable for the use of the first-order kinetic equation and the most suitable equations varied for different heavy metals.
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