Assessment of heavy metal pollution of gray forest soils of agricultural lands and their phytoremediation in the cultivation of milk thistle
The efficiency of removing heavy metals (lead, cadmium, zinc, copper) from gray forest soils in the cultivation of milk thistle has been studied. The research included field, laboratory method of atomic absorption, mathematical and statistical processing. We found that the content of lead, cadmium, zinc, and copper in the vegetative mass of milk thistle when grown on gray forest soils in the right-bank forest-steppe of Ukraine was 6.2 mg/kg, 1.25 mg/kg, 32.5 mg/kg, and 12.0 mg/kg, respectively. The high accumulation of heavy metals by milk thistle had a positive effect on the removal of lead, cadmium, zinc, and copper due to phytoremediation. Thus, 159 g and 1.12 g of lead; 31.9 g and 0.15 g of cadmium; 828.5 g and 11 g of zinc, and 306 g and 4.0 g of copper, respectively, are removed from the soil of each hectare with a vegetative mass and seeds of milk thistle with a yield of 25.5 t/ha. Thus, when growing milk thistle from gray forest soils per 1 ha of area for each growing season of this culture is made 160 g of lead, 32 g of cadmium, 839 g of zinc, and 310 g of copper.