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Abstract The effects of water-extractable Mn concentration, bioaccumulation factor (BAF), translocation factor (TF), and Mn uptake by Polygonum pubescens Blume cultured in the unexplored soil, mining soil and tailing soil from the Pingle Mn mine in China were quantified in a pot experiment to determine the effects of EDTA exposure on the success of phytoremediation. The results showed that EDTA significantly (P < 0.05) increased the water-extractable Mn concentration, and soils with different amounts of artificial disturbances had different responses to EDTA exposure. Low and medium EDTA concentrations might have positive effect on plant growth of P. pubescens cultured in the unexplored soil, as indicated by comparable increases in biomass, plant height and photosynthetic pigment content, but opposite results were found with high EDTA concentrations exposure. EDTA exposure had a negative effect on the growth of P. pubescens cultured in the mining soil and tailing soil. In general, the concentration of Mn in different tissues significantly (P < 0.05) increased as the EDTA concentration increased in each soil. The efficacy of Mn remediation by P. pubescens was enhanced in all three soils, with all EDTA treatments. Graphical abstract fx1 Highlights • EDTA exposure significantly increased the concentrations of water-extractable Mn in unexplored soil, mining soil and tailing soil. • EDTA exposure significantly increased the Mn accumulation in P. pubescens. • Low and medium EDTA concentrations played a positive role in the plant growth of P. pubescens cultured in the unexplored soil. • EDTA had negative effects on the growth of P. pubescens cultured in the mining soil and tailing soil. [ABSTRACT FROM AUTHOR]

Microbe-enhanced phytoremediation has been considered as a promising measure for the remediation of metal-contaminated soils. In this study, two bacterial strains JYX7 and JYX10 were isolated from rhizosphere soils ofPolygonum pubescensgrown in metal-polluted soil and identified as ofEnterobactersp. andKlebsiellasp. based on 16S rDNA sequences, respectively. JYX7 and JYX10 showed high Cd, Pb and Zn tolerance and increased water-soluble Cd, Pb and Zn concentrations in culture solution and metal-added soils. Two isolates produced plant growth-promoting substances such as indole acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and solubilized inorganic phosphate. Based upon their ability in metal tolerance and solubilization, two isolates were further studied for their effects on growth and accumulation of Cd, Pb, and Zn inBrassica napus(rape) by pot experiments. Rapes inoculated with JYX7 and JYX10 had significantly higher dry weights, concentrations and uptakes of Cd, Pb, Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg−1), Pb (200 mg kg−1) or Zn (200 mg kg−1). The present results demonstrated that JYX7 and JYX10 are valuable microorganism, which can improve the efficiency of phytoremediation in soils polluted by Cd, Pb, and Zn. [ABSTRACT FROM PUBLISHER]

Manganese contamination and toxicity have attracted greater attention recently due to its wide application in human life. However, less than 15 Mn hyperaccumulators have so far been documented worldwide. A wide-spread annual herb Polygonum pubescens Blume growing on Quanzhou Mn mine wasteland (south China) was found to contain Mn concentration up to 16,650 mg/kg (mean 14,480 mg/kg) in leaf dry matter, with a mean transfer factor (ratio of Mn concentration in leaf to that in root) at 4.6. Under the hydroponics culture conditions, the Mn levels in the tissues increased as the external Mn supplies rose, and leaf Mn concentrations exceeded 10,000 mg/kg from 1 nimol/L treatment onwards. At the harshest treatment (20 mmol/L), leaf Mn concentration peaked at 55,750 mg/kg, and about 97% of Mn taken accumulated in the aboveground parts. This fast-growing plant is a Mn hyperaccumulator and can be used for the phytoremediation of Mn-contaminated site. [ABSTRACT FROM AUTHOR]