ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 107, No. 3 (2020), p. 235–242
DOI 10.13080/z-a.2020.107.030

Leaching of potentially toxic elements from biochars intended for soil improvement



The current study investigated the effects of feedstock type and pyrolysis temperature on the leaching of potentially toxic elements (PTEs)  (Cu, Zn, Cd, Ni, Cr and Pb) from the biochar. The aim was to find out, which type of biochar would be best suited for soil improvement. Five types of feedstock were used: sewage sludge compost (SSC)  (1); the biomass of unfertilized (2) and fertilized with SSC (3) willow (Salix sp. cultivar ‘Tora’); the biomass of unfertilized (4) and fertilized with SSC (5) perennial mugwort (Artemisia dubia Wall.). It was found that the leaching concentrations of PTEs were higher of mugwort-based biochar in comparison to willow-based biochar. However, in the eluates of mugwort-based biochar, the biggest part of PTEs was bound in complexes with dissolved organic carbon. This means that PTEs in the eluates of mugwort biochar were less mobile and less toxic to soil organisms. PTEs leached from the biochar produced at a temperature of 700°C also were mostly in complexes with dissolved organic carbon. The leaching concentrations of PTEs were higher of the biochar produced from plants fertilized with SSC in comparison to the biochar produced from unfertilized plants (p < 0.05).

It is difficult to predict how the process of leaching of PTEs from the biochar would take place if this biochar were to be introduced into the soil. There are many factors that can affect this. It was found that PTEs leaching concentrations of the biochar did not always depend directly on the total concentrations of PTEs in this biochar. However, it is likely that unfertilized plant-based biochar produced at 700°C temperature would be more suitable for soil improvement.

Key words: Artemisia dubia, heavy metals, potentially toxic elements, Salix, sewage sludge compost.

Full text: 107_3_str30.pdf