Interaction among Heavy Metals in Landfill Leachate and Their Effect on the Phytoremediation Process of Indian Marigold

Abstract

Phytoremediation is considered an effective and economical method for metal recovery along with removing toxic chemicals from contaminated soil. The studies done so far concentrate on the factors responsible for uptake of a single heavy metal from the soil. However, in nature, pollutants are generally found as a mixture of various heavy metals. Furthermore, research related to phytoremediation of mixed contaminant sites such as landfills are focused on the selection of plants rather than heavy metal uptake pattern. Thus, it becomes important to understand how phytoremediation processes change in remediating a mixed pollutant with respect to removing single metal contamination. In the present study, the phytoremediation potential of Indian marigold is compared when the soil–metal concentration is individually spiked with Cd, Pb, Ni, and Cr salt solution against the remediation potential of marigold when the soil–metal concentration is spiked by landfill leachate (mixture of heavy metal) collected from the Gazipur landfill site, New Delhi, India. The result shows that the rate of metal accumulation is highly sensitive to metal concentration and metal interactions. When the soil–metal concentration is spiked with metal salts, their respective total uptake by marigold follows the order Cd > Pb > Cr > Ni with BCF > 1, TF > 2, and ECf > 1 for Cd and Cr making marigold a hyperaccumulator and with BCF < 1, TF > 2, and ECf < 1 showing an avoidance toward uptake of Pb and Ni. When the heavy metal accumulation pattern is studied for soil–metal concentration spiked by landfill leachate, the order of accumulation follows Cd > Cr > Pb > Ni with BCF > 1, TF > 2, and ECf > 1, and marigold is an accumulator for Cr. BCF > 1, TF < 2, and ECf < 1 stabilizes Cd and Pb add by leachate and there is no uptake of Ni after reaching a tolerance level of 555 µg/kg. The study is useful for understanding change in heavy metals uptake from heterogeneous sites for better landfill management.