Assessing the phytoextraction of cadmium, lead, and zinc from a slag-contaminated soil by legume species inoculated with rhizobial strains

Abstract

Abstract Metal-polluted soils can pose a severe threat to the environment and need remediation. We assessed the potential of jack bean and mucuna inoculated with rhizobial strains on the phytoremediation of soils contaminated by lead (Pb) smelting activities in Santo Amaro, Bahia state, the most serious case of Pb contamination in Brazil. Plants were grown in pots containing soils with three contamination levels for Pb, cadmium (Cd), and zinc (Zn) based on the distance from the chimney of the abandoned Pb smelter plant. Legumes and inoculated strains were tolerant to soil contamination. The BR 2811 strain is potentially indicated to increase jack bean biomass. The Cd, Pb, and Zn concentrations in plants were highest when grown on the soil with the highest contamination level. We found significant interactions between strains and soil contamination levels for phytoextraction efficiency, although the very high metal contents in soil can make phytoextraction unfeasible due to the time required to bring the metals to regulatory concentrations. The Cd, Pb and Zn net removal from soil was proportional to increased contamination levels. The legumes did not show potential for Pb phytoextraction, but they have the potential for Zn phytoextraction and Cd phytostabilization. The BR 2811, BR 3501 and BR 7606 strains were the most promising to increase the phytoremediation potential of jack bean and mucuna.