Efficiency of Phytoremediation of Soil Contaminated by Heavy Metals by Cultivation of Spotted Milk Thistle

Abstract

In contrast to air and water environments, soils do not have the ability to quickly clean, so toxic substances that enter it from the outside can be stored for a long time. At the same time, toxicants, being included in the food chain of soil - plants - living organisms, can reach high levels and have a long duration of action. It is known that the accumulation of heavy metals in the soil occurs under the influence of emissions from industrial enterprises, during irrigation with wastewater, removal of sludge to agricultural lands after wastewater treatment, due to the application of mineral and organic fertilizers, etc. When heavy metals affect soils, there is a change in the soil environment, the occurrence of erosion processes, contamination of agricultural products, etc., which necessitates the search for productive and safe methods of their cleaning. The article presents the results of a study of the effectiveness of phytoremediation of soil when growing milk thistle when it is fertilized in the conditions of the Right-Bank Forest-Steppe. Based on the results of the analysis of primary sources, the current problems of soil degradation, their contamination with heavy metals, and the role of phytoremediation are determined. As a result of the research, certain changes in the intensity of the removal of lead, cadmium and zinc from the soil were found when it was fertilized with mineral fertilizers - ammonium nitrate (60 kg/ha), simple superphosphate (60 kg/ha), potassium chloride (60 kg/ha), NPK mixture fertilizers (60/60/60 kg/ha) and organic fertilizers - humus (20 t/ha), sugar beet lime sludge compost (6 t/ha) and green manure (mustard). It was established that fertilizing gray forest soils with ammonium nitrate, simple superphosphate, potassium chloride, and a mixture of NPK fertilizers contributed to the increase of removal with vegetative mass and seeds of milk thistle: lead by 2.14 times, 54.3%, 52.2%, and 87.5 %; cadmium – 3.5 times, 41.9%, 71.1%, 2.2 times; zinc - 2.8 times, 22.7%, 20.1%, 2.6%, respectively. Fertilizing the soil with humus, sugar beet lime sludge compost, green manure increased lead removal from the soil by milk thistle by 60.1%, 42%, 3.9%; cadmium - by 58.0%, 31.3%, 3.2%, zinc - by 2.03 times, 24%, 13.6%, respectively.