Root-induced changes of Zn and Pb dynamics in the rhizosphere of sunflower with different plant growth promoting treatments in a heavily contaminated soil

Abstract Root induced changes are deemed to have an important role in the success of remediation techniques in contaminated soils. Here, the effects of two nano-particles [SiO 2 and zeolite] with an application rate of 200 mg kg −1 , and two bacteria [ Bacillus safensis FO-036b(T) and Pseudomonas fluorescens p.f.169] in the rhizosphere of sunflower on Zn and Pb dynamics were studied in greenhouse conditions. The treatments reduced the exchangeable Zn (from 13.68% to 30.82%) and Pb (from 10.34% to 25.92%) in the rhizosphere compared to the control. The EC and microbial respiration/population of the rhizosphere and bulk soil had an opposite trend with the exchangeable fraction of Zn and Pb, but dissolved organic carbon followed a similar trend with the more bioavailable fractions. As a result, the accumulation of Pb and Zn in the plant tissues was significantly (p 2 NPs and bacteria to immobilize Pb and Zn in the soil, depending on the chemical character of the metals and the treatments. Generally, the affinity of the biotic treatment for Pb was more than the abiotic and conversely, the abiotic treatment showed a higher ability to immobilize Zn than the biotic treatment.