Effects of Heavy Metal Pollution in Soil of Coal Gangue Area on Germination and Seedlings of Typical Remediation Plants

Abstract

The problem of soil heavy metal pollution caused by coal gangue accumulation areas is becoming more and more serious. In situ plant remediation technology has become one of the most promising methods to solve heavy metal soil pollution due to its advantages of the green economy. In this experiment, the characteristics of heavy metal pollution in the shallow soil (vertical depth 0~20 cm) 300 m outside the square circle of a typical coal gangue accumulation area in the Fengfeng Mining Area of Hebei Province, China were used as the prototype. Alfalfa and ryegrass were selected as the test plants. Pot experiments were carried out at different heavy metal concentrations (Cu:14/64/100 mg/kg, Pb:15/38/170 mg/kg, Cd:1/4/8 mg/kg) levels to study and reveal the effects of single and compound soil heavy metal pollution on seed germination and seedling growth characteristics of alfalfa and ryegrass. The results showed that: (1) Under the condition of single Cd pollution, the germination index of alfalfa seeds and the germination potential of ryegrass seeds show a trend of “low concentration promotion and high concentration inhibition”. Under the condition of single Pb and Cu pollution in soil, the germination indices show obvious inhibition and damage effect; that is, with an increase in concentration, the germination rate, germination potential, germination potential, and vigor index show a decreasing trend. When Pb is 170 mg/kg or Cu is 100 mg/kg or Cd is 8 mg/kg, the inhibitory effect on seed germination and seedling growth of the two plants is the most harmful. (2) Due to the different concentrations of heavy metal combined pollution, there are synergistic or antagonistic effects between Cu, Pb and Cd in soil on alfalfa and ryegrass. That is to say, under low concentrations of heavy metal pollution, the inhibitory effect of combined stress is greater than that of single stress, and under high concentration of heavy metal pollution, the inhibitory effect of combined stress is less than that of single stress. (3) Whether in the single pollution or combined pollution of soil, ryegrass is always more tolerant than alfalfa, indicating that ryegrass has more potential for remediation.