Effect of Citric Acid, Rhizosphere Bacteria, and Plant Age on Metal Uptake in Reeds Cultured in Acid Mine Drainage

Abstract

Acid mine drainage (AMD) poses serious environmental problems. This study assessed the effect of plant age, rhizosphere bacteria, and citric acid (CA) on the metal plaque formation and metal uptake in Phragmites australis cultured in a synthetic AMD solution. Iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque, which slightly decreased Fe and Mn uptake. CA reduced the growth of Fe(II)OB and formation of Fe plaque, thereby increasing the Fe and Mn accumulations in reeds. Adult reeds had developed more Fe plaque on the root surface than seedlings. However, the adult reeds still accumulated higher concentrations of metals due to their higher tolerance to toxic environments and bigger biomass. With 9.02 g/L CA, adult reeds accumulated 0.51 ± 0.00 mg Mn, 109.38 ± 1.37 mg Fe, and 1.77 ± 0.04 mg Al. More investigation may be needed to further study the effect of CA when applied to AMD-contaminated field.