Characteristics of heavy metals in soil of lead-zinc mining areas and changes of antioxidant enzyme systems in maize leaf under Pb stress

Pb, Cu, Cd, Zn content of soil in mining areas and abandoned land, flats of the Pijiang River and farmlands were investigated. On this basis of soil heavy metal pollution, the changes of antioxidant enzyme system in maize (Qiandan 88) under different Pb concentrations (0, 20, 40, 60, 80, 100, 150, 200, 500, 1000, 2000, 3000 mg/L) stress were studied. The results show that the content of Pb, Cu, Cd, and Zn in soil is the highest in mining areas and abandoned land, followed by flats of the Pijiang River > farmlands, and that the variation range of Pb, Cu, Cd in mining areas and abandoned land are 106.40-2564.72, 14.83-490.88, 22.57-712.77 mg/kg, respectively, which are higher than that of the other land use types. When maize is under stress of 20-500 mg/L Pb concentration, T-SOD activity of maize leaves increase with the increase of Pb concentration and the highest value is 50.21 U/mg prot, but under Pb concentration > 1000 mg/L stress, T-SOD activity of maize leaves decrease gradually. The activity of POD decreases with the increases of Pb concentration, and the lowest POD activity of leaves in maize with the value of 93.24 U/mg prot is appeared in Pb 1000 mg/L concentration treatment group. MDA content in leaves of maize increases with the increase of the Pb concentration and the highest value is 101.98 nmol/mg prot, then the content of MDA decreases gradually when the Pb concentration is more than 500 mg/L, which indicates that the membrane lipid peroxidation of maize leaves under high concentration of Pb stress is serious and leads to the cell damage.

Automated summary

The content of heavy metals Pb, Cu, Cd, and Zn in soil was investigated in mining areas, abandoned land, flats of the Pijiang River, and farmlands. The study also examined the changes in the antioxidant enzyme system of maize (Qiandan 88) under different Pb concentrations. The results showed that the highest content of Pb, Cu, Cd, and Zn was found in mining areas and abandoned land, followed by flats of the Pijiang River and farmlands. Maize leaves showed an increase in T-SOD activity with increasing Pb concentration up to 500 mg/L, but a decrease in T-SOD activity at Pb concentration above 1000 mg/L. POD activity decreased with increasing Pb concentration, and MDA content in leaves increased with increasing Pb concentration up to a certain point and then decreased. This suggests that high Pb concentration leads to membrane lipid peroxidation and cell damage in maize leaves.