Changes of three organic acids in the process of Cd and Pb phytoextraction by Helianthus annuus L.

In the present study, sunflower was used to enrich the cadmium (Cd) and lead (Pb) in sand culture, and the changes of metals uptake, organic acids, pH, and redox potential were investigated. Results showed that the Cd and Pb accumulation was dissimilar in treatments. In single treatments of Cd or Pb, the amount of glutaric and lactic acids decreased with concentrations; the secretion of glutaric and glycolic acids in 5 mg/L Cd treatments were the highest at the 90th day. In the mixed treatments of Cd and Pb, glutaric acids in cultures with Cd 5 mg/L + Pb 50 mg/L and Cd 10 mg/L + Pb 100 mg/L were higher than those in other treatments. Both lactic and glycolic acids reached the highest values in Cd 10 mg/L + Pb 100 mg/L treatments at the end of experiment. Besides, the Cd or Pb uptake showed various correlations with pH, redox potential, and organic acids, the reason might be that the presence of Cd or Pb influenced the organic acids exudation, and alterations of rhizosphere, including acidity, redox potential, and organic acids, impacted the bioavailability and phytoextraction of toxic metals conversely.