**5. Conclusions**

The study of the adaptive characteristics of *Echinochloa frumentacea* revealed that soils with a high degree of contamination with a complex of HMs and petroleum products have an inhibitory effect on the germination and growth processes of *Echinochloa frumentacea*: on the most polluted soils of the Embankment, a reduction in seed germination by 21–23% and a decrease in growth parameters up to 3 times were observed.

A low level of contamination with the complex of HM in the sanitary protection zones of metallurgical industries did not have a toxic effect on seed germination and stimulated the quantitative characteristics of photosynthetic pigments and AOS of *Echinochloa frumentacea*: the content of chlorophylls and low molecular antioxidants such as ascorbic acid and glutathione (GSH) increased by 9–53%, 17–19%, and 5–15% respectively. The data obtained indicate good adaptive characteristics of *Echinochloa frumentacea* to technogenic pollution of soils by metallurgical enterprises.

The accumulation of *Echinochloa frumentacea* biomass on contaminated soils varied within 4280–7920 kg/ha. The increase in shoot biomass in relation to plants on background soils was shown for plants grown on metallurgical enterprises soils. The polyelement pollution of soils of the SPZ and of the highway contributed to the accumulation of the dry mass of plants compared to background soils.

*Echinochloa frumentacea* is not suitable for Mn, Co, As, and Cd accumulation from soils with polyelement contamination. The bioaccumulation of Pb was maximum in the root system and constituted 1.57–7.38 mg/kg dry weight. V from polluted soils mainly accumulated in the roots. The main method of V accumulation from soils is rhizofiltration. The accumulation of Cu by the shoots and root system of plants makes it possible to consider *Echinochloa frumentacea* as a Cu phytoremediant. The removal of Zn from contaminated soils during a short vegetation period (1.5 months) was 168–508 g/ha. The obtained values make it possible to recommend *Echinochloa frumentacea* for Zn removal from soils with polyelement anomalies in combination with other species accumulating the element, in intercrop mixtures.

The minimal number of all groups of microorganisms studied (on average, two times lower than in the uncontaminated background soil) was noted in the Embankment soil, which contains the highest concentrations of both inorganic (heavy metals) and organic (petroleum products) pollutants. A two-fold increase in the number of bacteria was observed in the rhizosphere of plants grown in the soils of Tulachermet and Lenin Ave., and a 1.7-fold increase in the number of actinomycetes and a 1.5-fold increase in the number of micromycetes were observed in the soil of KMP, which could be due to specific plant stimulation of microbial taxa resistant to heavy metals.

The rhizosphere populations of *Echinochloa frumentacea* grown in the background soil of Yasnaya Polyana were characterized by the lowest taxonomic diversity compared to the rhizobiomes of plants grown in contaminated urban soils. The species richness index was maximal for rhizosphere communities of plants grown on Tulachermet soils.

The data of metagenomic analysis characterizing the rhizospheric microbiome of *E. frumentacea* plants grown on different soils make it possible to assume that the dominant families are Gaiellaceae and Nocardioidaceae (Actinobacteria), Sphingomonadaceae, Hyphomicrobiaceae, Comamonadaceae, Oxalobacteraceae, and Xanthomonadaceae (Proteobacteria), and the families Pirellulaceae (Planctomycetes), Cytophagaceae, and Chitinophagaceae (Bacteroides) can participate in the formation of the rhizobiome of *E. frumentacea*.

Further detailed study of the properties of the selected microorganisms will make it possible to select a promising inoculant to improve plant growth on contaminated soil to increase the efficiency of its phytoremediation.

**Author Contributions:** Conceptualization S.V.G., A.K. and A.Y.M.; methodology S.V.G., A.Y.M., I.Z. and O.I.O.; software A.Y.M., I.Z. and O.I.O.; validation A.Y.M., S.V.G., I.Z. and O.I.O.; formal analysis S.V.G., A.Y.M., I.Z. and O.I.O.; investigation S.V.G., A.Y.M., I.Z. and O.I.O.; resources RFBR; writing—S.V.G., A.K., A.Y.M. and I.Z.; visualization, S.V.G., A.Y.M. and I.Z.; supervision S.V.G.; project administration S.V.G.; funding acquisition S.V.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Russian Foundation for Basic Research project No 19-29- 05257 "Technogenic soil pollution with toxic elements and possible methods for its elimination".

**Acknowledgments:** The study was carried out with financial support by the Russian Foundation for Basic Research project No 19-29-05257 "Technogenic soil pollution with toxic elements and possible methods for its elimination".

**Conflicts of Interest:** The authors declare no conflict of interest.
