The effect of different levels of leachate on phytoremediation of pyrene-contaminated soil and simultaneous extraction of lead and cadmium

Abstract

Pyrene is one of the 16 group combinations of polyaromatic hydrocarbons, which are known as primary pollutants in the U.S. Environmental Protection Agency (USEPA) list. This study aimed to investigate the cross effect of different levels of landfill leachate on phytoremediation of pyrene-contaminated soil using the sorghum bicolor plant. The study parameters included the presence or absence of the plant, different concentrations of pyrene (150, 300, 500, 750, and 1000 mg kg−1), time (30, 60, and 90 days), and different levels of irrigation with leachate (0, 30, 50, 70, and 100%). Soil pyrene was measured every 30 days, and heavy metals (lead and cadmium) added to the soil by irrigation with leachate were measured in the soil and the plant at the end of 90 days. According to the results, pyrene removal efficiency after 90 days was 96% in irrigation treatments with 30% leachate in the presence of the plant and 67% in irrigation treatments with tap water in the presence of the plant. In addition, 95% of lead and 49% of cadmium added to the soil by irrigation with 30% leachate were extracted from the soil by the sorghum bicolor. According to the results, by increasing nutrients and number of soil bacteria during the cross treatment, landfill leachate increased the pyrene removal efficiency significantly during phytoremediation (p < 0.006) and the sorghum bicolor plant extracted the lead and cadmium of the leachate. In non-planting treatments, although adding high levels of leachate to the soil significantly improved the pyrene removal, it caused the levels of heavy metals, such as lead and cadmium, to exceed the allowable limit (p < 0.001).