Biological effects of biochar and zeolite used for remediation of soil contaminated with toxic heavy metals.

Biochar and zeolite are widely used in the remediation of soil contaminated with toxic heavy metals. However, the interaction of these amendments and their effects on grass productivity have not been comprehensively summarized. The aim of this study was to investigate the biological effects of zeolite and biochar used as soil amendments in the process of remediating soil contaminated with Cd, Pb and Zn. In a pot experiment, the following treatments were applied: zeolite, biochars produced at temperatures of 350 °C and 550 °C, mixtures of biochars and zeolite, and a control treatment without any amendments. The soil amendments were tested on two grass species: tall fescue (Festuca arundinacea Schreb.) and cocksfoot (Dactylis glomerata L.). The root morphometric parameters and aboveground production were determined in 2017 and 2018.Higher biomass production was observed in the tested grasses in the treatments with zeolite alone (0.229 kg DM m-2) or mixed with the biochars (0.239 kg DM m-2) than in control treatment (0.029 kg DM m-2). Zeolite used in contaminated soil significantly affected root biomass and root morphology parameters. Zeolite application resulted in significantly higher root biomass (2.30 mg cm-3) and root length (76.61 cm cm-3) than those in the treatments without zeolite (0.29 mg cm-3 and 6.90 cm cm-3). Biochar as a soil amendment did not affect most root morphometric parameters. The application of biochars only slightly reduced the root diameter of cocksfoot. The root diameter of tall fescue was similar in all treatments (0.075 mm) except the control (0.063 mm) and biochar 550 treatments (0.067 mm), in which slightly thinner roots were observed.