Stabilization of Heavy Metal Contaminated Soil Around an Abandoned Mine Using Starfish(Asterina pectinifera) and Cockle Shell

Abstract

Objectives:The soil around waste mine sites can be contaminated with heavy metals by mine tailings and leachate, and heavy metals can accumulate in the body through crops harvested from contaminated soil. The stabilization method is often applied to the restoration of contaminated soil around abandoned mines, but it is necessary to develop natural stabilizers that are not harmful to the environment. In this study, starfish(<i>Asterina pectinifera</i>) and cockle shells were evaluated as stabilizers for arsenic and heavy metal(Pb, Zn) contaminated soil.Methods:Starfish and cockle shells were processed into -#10 mesh, -#20 mesh, and calcined (900℃, 2hr) -#10 mesh to evaluate their characteristics through XRD and XRF analyses. The stabilized soil was eluted at 0.1 N HCl. Then the stabilization efficiency was evaluated with ICP-OES analysis, and the stabilization mechanism was identified with SEM-EDX analysis. Afterwards, lettuce was cultivated in the stabilized soil and the concentration of heavy metals transferred from the soil to the lettuce was evaluated.Results and Discussion:The calcination process converts the CaCO₃ in the natural stabilizer into CaO. Arsenic and heavy metals are effectively immobilized within the soil through pozzolanic reactions and Ca-As precipitation. Nitric acid decomposition of lettuce grown in the stabilized soil demonstrated the absence of arsenic, meeting the safety standards outlined in the Korean Food Standard Codex.Conclusion:The stabilization of soil contaminated with arsenic and heavy metals by starfish and cockle shell was confirmed to be attributed to pozzolanic reactions and the formation of insoluble precipitates. In addition, they could be used as natural waste stabilizers based on their high calcium carbonate content.