Effects of Salinization, Oil Contamination, and Heavy Metals on Soil Biological Activity and Phytoremediants

Using plants to restore soils subjected to salinization and polychemic pollution can be an effective way to return agricultural land to circulation and obtain safe products. In this study, experiments were conducted with oats and lupine to evaluate their ability to purify soils contaminated with copper (II) and nickel (II) ions, carbonate and sulfate anions and oil and their combinations. The biological activity of the soil, phytotoxicity, and hydrocarbon content, as well as plant growth and biochemical parameters in polluted soil, were studied. The enzymes most sensitive to soil contamination were catalase, urease, and phosphatase. Copper ions inhibited oat root growth by 45.7% and lupine by 46.6%. Oil and its mixtures with other pollutants inhibited shoot growth by up to 50.3% in oats and up to 28.6% in lupine. The content of malonic dialdehyde increased in oats when exposed to copper, while in lupines, it increased 2.9-fold when exposed to oil. Flavonoids in oats increased with metal contamination (by 9-16.7%), while in lupines with oil (by 8.6%). Chlorophyll fluctuations were less pronounced in oats than in lupine. Despite the stress experienced by plants due to soil pollution, the degradation rate of petroleum hydrocarbons under oat and lupine crops was 33-46%. In general, oats and lupine are promising for the phytoremediation of complexly polluted and saline soils.