Effects Of Leaching Desalination On The Vertical Movement Of Heavy Metals In Tidal Flat Soils

Based on the tidal flat soil in the Pearl River estuary,the heavy metal concentrations and soil physical and chemical properties such as Eh,pH of pore water and moisture content in different stages of desalination and vertical depths were investigated through leaching experiment.The vertical movement of heavy metals during leaching was studied,so as to provide a theoretical basis for the cleanup and safe use of the polluted tidal flat soil.The results showed that:With the increase in the depth of soil column,the reducibility of soil and salinity increased either,but the moisture content decreased. The conductivity of pore water decreased during leaching for the same soil layer.The concentrations of Cd,Pb and Cr in the pore water increased with the increase in the depth of soil column.Water-soluble Zn and Cu concentrations decreased rapidly in the beginning of leaching.Then they remained relatively stable.Ni wasn't detected.The total average concentrations of Cd,Pb and Cr in the pore water decreased with the decrease of salinity in surface soils.Leaching desalination promotes the downward movements of heavy metals in surface soils during reclamation.The heavy metals accumulation in soil showed different characteristics during the leaching desalination.Study from the total average concentration of heavy metals of each treatment,the concentrations of Cd,Pb,Cr,Zn and Cu in soils increased with the increase in the depth of soil column.After leaching,the percentage of Cd and Pb concentration decrease was highest,followed by Zn,Cu and Cr,the percentage of Ni concentration decrease was minimum.