Combined Effects of Microbial Inoculation and Activated Carbon/Biochar on the Accumulation and Transfer of Nutrients and Potentially Toxic Metals in Maize Plants Grown on a Contaminated Soil

This study was conducted in a greenhouse pot experiment to assess the effects of biochar (BC) or activated carbon (AC) alone or in combination with arbuscular mycorrhizal fungus (AMF) Glomus mosseae or acid-producing bacteria (BA) Bacillus polymyxa on plant growth, EDTA-extractable Cd and Pb, and contents of heavy metals (Cd and Pb) and nutrients (Ca, Mg, K, and P) in maize (Zea mays L.) grown on sewage wastewater contaminated soil. The results showed that most treatments with BC, AC, or its co-application with microbial inoculation led significantly to greater nutrient uptake and promoted growth of maize than non-treated plants. Additionally, the soil additives used decreased the amounts of EDTA-extractable Cd (by 28.7%-100%) and Pb (by 22.8%-94.3%). The applied treatments caused significant decreases in Cd concentrations and the bioconcentration factor (BCF) of Zea mays. The highest shoot Cd reduction was observed for AC (53%), followed by AC+BA (36.9%) > AMF (34.5%) > AC+AMF (28.5) > BA (28.3%) > BC+BA (26.1%) > BC (22.7%). However, more Cd was accumulated in the roots of plants treated with AMF by 63.7% with a lower value of translocation factor (TF) compared to control soil. In contrast, the treatments increased the levels of Pb in the maize plants, and BC coupled with AMF showed the greatest Pb accumulation. It could be concluded that the investigated additives can be applied as immobilizing agents for Cd in the soil but maize plants as phytoextractants for both metals in sewage-contaminated soil are not feasible, as indicated by insufficient phytoextraction efficiency.