Remediation of acid mine drainage (AMD)-contaminated soil by Phragmites australis and rhizosphere bacteria

Abstract

Experiments were conducted to assess the impact of citric acid (CA) and rhizosphere bacteria on metal uptake in Phragmites australis cultured in a spiked acid mine drainage (AMD) soil. Rhizosphere iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque on roots, which decreased the uptake of Fe and Mn. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque, raised the metal mobility in soil, and increased the accumulation of metals in all tissues of the reeds. The higher the CA dosage, the more metals accumulated into reeds. The total amount of metals in reeds increased from 7.8 ± 0.5 × 10(-6) mol plant(-1) (Mn), 1.4 ± 0.1 × 10(-3) mol plant(-1) (Fe), and 1.0 ± 0.1 × 10(-4) mol plant(-1) (Al) in spiked soil without CA to 22.2 ± 0.5 × 10(-6) mol plant(-1) (Mn), 3.5 ± 0.06 × 10(-3) mol plant(-1) (Fe), and 5.0 ± 0.2 × 10(-4) mol plant(-1) (Al) in soil added with 33.616 g C6H8O7·H2O for per kilogram soil. CA could be effective at enhancing the phytoremediation of metals from AMD-contaminated soil.