ИСТИНА

One of the most important problems of our time is erosion and land degradation. In this regard, techniques and technologies aimed at preserving soil and their fertility are actively developing. One of the promising methods is the usage of synthetic and natural polymers. One of these polymers are humic substances, in the form of industrial preparations, which are widely used as biostimulants. It is also possible to use other biopolymers as soil meliorants, in particular heterofunctional polysaccharides such as xanthan gum. Due to the property of forming net structures, it is able to retain moisture, and also has a beneficial effect on the soil structure. The aim of the study is to evaluate the impact of two-component polyelectrolyte compositions based on xanthan gum (XG) and 3 types of humic products (HP) on the detoxifying properties of sod-podzolic soil in a model experiment with heavy metal (HM) pollution and to identify their potential as soil meliorants in comparison with individual polymers. The object of the study was the arable horizon of a sod-podzolic soil. Following 4 polyelectrolytes have been used: XG and 3 HP different in organic matter source: “Sakhalin humate” from lignite (Sh), “Peat gel” from peat (Pg) and “Lignohumate” from lignosulphonate (L) and combinations: XG + Sh, XG + Pg and XG + L. HPs were examined for several properties such as content of organic carbon, elemental composition, content of acidic functional groups. The model experiment was carried out as follows: 100 grams of soil were mixed with 1 gram of dry polymers, then moistened with 15 milliliters of water. Incubated for 2 weeks at room temperature. In a parallel series of experiments, soil-polymer mixtures were spiked with nitrate solutions of Cu, Zn, Pb at a dose of 150 mg/kg of each element. The experiment was carried out in three parallels. After incubation soil pH, content of organic carbon and mobile species of heavy metals were determined. Also phytotoxicity of soil-polymer mixtures was assessed in bioassay with a test culture (Raphanus sativus). The following results were obtained during the study: 1. The highest content of organic carbon belonged to L (29,81%), the lowest belonged to Pg (8,36%), but Pg had the highest content of nitrogen (1.49%). Also Sh had the largest number of acidic functional groups (4,12 mg*eq/g). 2. The introduction of all types of studied polymers in a dose of 1g/100g of soil increases the total carbon content in soil (by 0.5%-0.9% compared with the control). 3. Among the individual polyelectrolytes the most effective binding of Cu, Pb and Zn was showed by Sh and made up accordingly 34%, 21% and 20% of binding. Pg and L alone perfomed less effective but in binary composition with XG their efficiency in decreasing mobility of heavy metals enhanced by an average of 10%. 4. Both individual polyelectrolytes and their binary compositions had a stimulating effect on the test culture. This influence affected the length of the stems of the seedlings more than the roots. L alone was the most effective polyelectrolyte in this case and enlarged stems by 2,2 times. The compositions with XG did not show a better effect on the growth of seedlings compared to individual polyelectrolytes.