Phytoremediation of arsenic in mine tailings by Acacia Mangium

Abstract

Old mining areas are always associated with metal contamination such as arsenic due to poor waste management and pose a significant threat to human health due to dispersion of toxic metal-containing particulates in air, soil, and water. Therefore, the goals of this project are to investigate the potential of Acacia mangium to remediate mine tailings through phytoremediation and explore its ability to survive on contaminated and low nutrient soil. Tailings characterization studies shows that the soil texture is sandy clay, with pH around 4.5 and the highest heavy metal content in the soil is arsenic with concentration 790 mg/kg. The HPLC-ICP-MS results found that there was only arsenate in the tailings and no arsenite was detected. A preliminary test using soil spiked with various arsenic concentrations showed that Acacia mangium was able to survive on arsenic-contaminated soil with concentrations up to 500 mg/kg arsenic. Ex-situ phytoremediation studies using mine tailings showed no toxicity effect on the Acacia mangium throughout the five months of treatment. Bioconcentration and translocation factor indicate that Acacia mangium utilize phytostabilization as its main mechanism to uptake arsenic into the plant’s tissues. The usage of chemical enhancement, monoammonium phosphate (NH4H2PO4) and citric acid (C6H8O7), had improved the dry weight biomass (roots, stems and leaves) and arsenic uptake by the roots of Acacia mangium. Moreover, 50 mg/kg of phosphate concentration had increased the translocation of arsenic from the roots to the stems by 12-fold increase compared to the un-dosed plants. Further speciation analysis revealed that arsenic in the form of arsenate was the only arsenic species detected in the stems after being amended with monoammonium phosphate; thereby, suggesting a sensible strategy for more efficient targeted arsenic phytoremediation by Acacia mangium.