• Energy Research
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In response to the growing threat to the quality of the soil environment, new technologies are being developed to protect and remediate contaminated sites. A new approach, namely, assisted phytostabilization, has been used in areas contaminated with high levels of potentially toxic elements (PTEs), using various soil additives. This paper determined the effectiveness of biochar-assisted phytostabilization using Dactylis glomerata L. of soil contaminated with high concentrations of the selected PTEs (in mg/kg soil): Cu (780 ± 144), Cd (25.9 ± 2.5), Pb (13,540 ± 669) and Zn (8433 ± 1376). The content of the selected PTEs in the roots and above-ground parts of the tested grass, and in the soil, was determined by atomic absorption spectrometry (AAS). The addition of biochar to the contaminated soil led to an increase in plant biomass and caused an increase in soil pH values. Concentrations of Cu, Cd, Pb and Zn were higher in the roots than in the above-ground parts of Dactylis glomerata L. The application of biochar significantly reduced the total content of PTEs in the soil after finishing the phytostabilization experiment, as well as reducing the content of bioavailable forms extracted from the soil using CaCl2 solution, which was clearly visible with respect to Cd and Pb. It is concluded that the use of biochar in supporting the processes of assisted phytostabilization of soils contaminated with PTEs is justified.

Objective: Biochar and a commercial humic acid-rich product, Humac (modified leonardite), represent soil amendments with the broad and beneficial effects on various soil properties. Their combination has been scarcely tested so far, although the positive impact of their interaction might be desirable. Materials and Methods: The dehydrogenase activity (DHA), microbial biomass carbon (Cmic), soil respiration (basal and substrate-induced), enzyme activities, total carbon (Ctot), and both shoot and root biomass yield were measured and compared in the short-term pot experiment with the lettuce seedlings. The following treatments were tested: the unamended soil (control), the Humac-amended soil (0.8 g·kg−1), the biochar-amended soil (low biochar 32 g·kg−1, high biochar 80 g·kg−1), and the soil-amended with biochar + Humac. Results: The effect of both amendments on the soil pH was insignificant. The highest average values of Ctot and Cmic were detected in high biochar treatment and the highest average values of basal and substrate-induced respiration (glucose, glucosamine, alanine) were detected in the low biochar treatment. The phosphatase activity and fresh and dry lettuce aboveground biomass were the highest in the low biochar + Humac treatment. Conclusions: Even though the combination of both biochar + Humac decreased the microbial activities in the amended soil (Cmic, DHA, enzymes, substrate-induced respiration) at the low biochar dose, they mitigated the detrimental effect of the high biochar dose on respiration (all the types) and the enzyme (phosphatase, arylsulphatase) activities. In contrast to the previously published research in this issue, the effects could not be attributed to the change of the soil pH.