Remediation On Reclaimed Tidal Soil Polluted With Heavy Metals By Sea-water Leaching Combined Eh Alternating Change

Presently, heavy metal pollution of beach reclamation soil is increasingly worse,to find effective and practical treatment methods is imminent. In this paper, in situremediation farmland through simulation experiments has been performed, usingartificial seawater to immerse and leach the soil, regulating soil redox potential bydrying time and immersion which were used to study the removal efficiency andmechanism of heavy metals through combining alternating changes of soil redoxpotential with seawater leaching of heavy metals in the soil. The experiment includedtwo treatment process, and each of them contained two stages, at the first stage,controlling soil and seawater immersion time to reach the targeted oxidation-reduction potential, then draining and drying, increasing redox potential, and finallywith seawater leaching. At the second stage, target soil oxidation-reduction potentialwas repeated as the first stage of the experiment. Targeted soil redox potential were byimmersion treatment in processing1-50mV for the first stage and-100mV for thesecond stage, and in processing2-100mV for the first stage, the-200mV for thesecond stage.On condition of Soil redox alternating and water leaching, removal rates ofheavy metals were different,those of Cd and Cr were best. Cd and Cr leachingremoval rate reached35.07%and33.84%through processing1, but reaching56.60%and39.16%by processing2. Treatment effect by processing2was better thanprocessing1, which indicating that with the decrease of soil redox potential theleaching removal rates of heavy metals in soil increased. exchangeable, carbonate,reducible and oxidizable concentrations of Cd, Zn, Pb, and Cr,, were significantlyreduced,, in which the majority of reducible heavy metals were removed, followed byOxidizable, but residual heavy metals showed no significant change. Moreover,Reducible heavy metal removal rates lift with redox potential reducing.In the leaching process of soil and seawater redox alternating, the activity ofsoil iron oxide sand dissolved organic matter and sulfur content increased with theincrease of immersion, while they decreased with leaching and drying time. It is useful for heavy to move from solid phase to liquid phase when activity of iron oxideand dissolved organics increased which removed heavy by water leaching. Otherwise,sulfide content of the soil increased, which is not in favour of removing for heavymetals from the solid to the liquid phase.