Mono-and co-applications of Ca-bentonite with zeolite, Ca-hydroxide, and tobacco biochar affect phytoavailability and uptake of copper and lead in a gold mine-polluted soil

Abstract We assessed the efficacy of Ca-bentonite (CB) alone and combined with Ca-hydroxide (CH), tobacco biochar (TB), and zeolite (ZL) aiming to immobilize Cu and Pb and decrease their bioavailability and uptake by pak choi followed by maize in a mining contaminated soil. The CB alone was able to decrease the availability and uptake of Cu and Pb by pak choi and maize. The mono- and multi-combination of CH, TB, and ZL with CB showed contradictory impact on the availability and uptake of Cu and Pb as compared to the mono-application of CB. The combination of CB with ZL and CH + ZL reduced the uptake of Pb by pak choi and maize, while the combination of CB with TB and ZL reduced the uptake of Cu by pak choi and maize as compared to the mono-application of CB. The co-application of CB with CH increased the phytoextraction of Cu by maize and Pb by pak choi shoots as compared to the mono-application of CB. We conclude that modified clays such as CB alone or combined with ZL, TB, and/or CH might be suitable candidates for phytomanagement of Cu and Pb contaminated soils.