Vanessa Katherine Kalero

The effect of polymer soil amendments on changes in toxicity of agro-sod-podzolic soil spiked with a complex of heavy metals (HM) has been characterized. Hydrolyzed polyacrylonitrile (HYPAN) and a binary composition of HYPAN+potassium humate (HYPAN+PH, 1:10) were applied at a rate of 0.2% (on a dry matter basis) to soils with model contamination by Cu, Zn, Pb, and Cd at levels of 2, 4, and 6 approximate permissible concentrations (APC). Samples without ameliorant treatment served as a control for all soil pollution levels. The effect of polymer formulations on reducing the toxicity of heavy metals manifested to varying degrees depending on the level of soil contamination. The bacterial standard bioluminescent biotest and phytotesting on the seedlings of higher plants Sinapis alba L. showed a positive effect of the HYPAN+PH composition at the highest contamination level, 6 APC. Bioindication of the functional state of soil microbiota showed that ameliorants lowered the microbial metabolic coefficient (to an acceptable level of 2 µg C-CO₂ mg⁻¹·Cmic·h⁻¹), which is important evidence of their positive effect on the soil microbial community. Laboratory biotesting of uncontaminated soil, as well as at relatively low levels of HM contamination, revealed the toxicity of the aqueous extract of samples with ameliorants (inhibiting root growth and quenching bioluminescence in bacterial bioassay). In light of the findings of this study, it is recommended that further analyses should be conducted before suggesting the use of tested ameliorants for the detoxification of polluted soils.

In a model experiment, the effect of polymer sorbents of different origins on the content of mobile species of heavy metals (HM) in zonal soils of the East European Plain was examined in a case study using soils of the Tula Region. Both synthetic and natural sorbents were used: hydrolyzed polyacrylonitrile (HYPAN), a binary structure of HYPAN and potassium humate (Humate “Sakhalinsky”), and a fungi mycelium powder (Micosorbent A). The experiment was conducted on four types of agricultural soils (Umbric Albeluvisols, Greyic Phaeozems, Voronic Chernozems) sampled in the Tula region in 2024 and spiked with Cu+2, Zn+2, Pb+2, and Cd+2 salts in 6 threshold limit values (TLV). It has been established that the same sorbent showed a significantly different remediation effect on different soil types with the same level of metal contamination: copper was bind from 30% on Voroic Chernozems to 50% on Greyic Phaeozems soils. For lead, the highest percent of mobile species to total was observed in Umbric Albeluvisoils (72%) and the lowest in Voronic Chernozems (56%). The application of Alternaria alternata mycelium had an effective effect on the sorption of zinc and cadmium in the studied soils: up to 70% in Voroic Chernozems for cadmium and up to 85% in Umbric Albeluvisoils for zinc.