The environmental impacts of air transport and air transportation systems have become increasingly important and are heavily debated. The aim of the study was to determine the degree of soil contamination by the potentially toxic elements (Cu, Ni, Pb, and Zn) in the vicinity of the airport runway and to evaluate whether airport traffic has had factual toxic effects on airport vegetation. The overall assessment of soil contamination by means of the Nemerow integrated pollution index indicated slight pollution; evaluation by the geoaccumulation index evinced moderate contamination by Zn and nonexistent to moderate contamination by Cu, Ni, and Pb. A significant difference between the take-off and landing sections of the runway was not statistically confirmed. The vegetation risk assessment by means of the potential ecological risk index (RI) showed the low ecological risk, while the phytotoxicity test revealed an inhibition of up to 33.7%, with a slight inhibition of 16.7% on average, and thus low toxic effects of airport traffic on airport vegetation. The results of the linear regression model between phytotoxicity and RI manifested no relation between the two. The outcomes from other studies suggest that the range of elements and the extent of contamination can be highly variable at different airports and frequently affected by car traffic. Therefore, further research on this issue is needed for the more precise determination of the elements emitted by air traffic at airports.
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.
