Phytoremediation of Heavy Metals and PAHs in Alkaline Slag Fill at a Wet Meadow Site

The feasibility of using phytoremediation to remediate an alkaline-slag-filled wet meadow site contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals has been studied. The objective of the present work is to investigate the ability of nine native grasses and trees to survive and remediate PAHs such as benzo(a) pyrene (BaP) and heavy metals such as arsenic (As), chromium (Cr), lead (Pb), and manganese (Mn) existing at the site during the three complete growing seasons. Replicate test plots were prepared by tilling and homogenizing the fill material to approximate depth of approximately 0.3 m. Soil samples from each plot were collected before and after preparing the test plots and analyzed for physicochemical properties and contaminant concentrations. The survival and growth of the plant species were monitored for two growing seasons. Only one plant species out of the total nine initially planted, specifically False Indigo Bush (Amorpha fruticosa) (FIB), survived the three growing seasons. Soil, plant root, and plant shoot samples were collected at the end of the second and third growing seasons at the plot where FIB was planted. PAHs and heavy metals were analyzed in the soil and plant samples. In addition, a sequential extraction procedure was followed to determine the fractionation of the heavy metals in soils before and after planting. The results showed no significant decrease in BaP, As, Cr, and Pb concentrations in the soil. In addition, there were no significant changes in heavy-metals fractions. However, Mn uptake in roots and shoots was observed, with a corresponding decrease in soil, at the end of the third growing season. The adaptability and survival of FIB and its high tolerance to harsh site conditions (high pH, fluctuating moisture, and contaminant toxicity) demonstrated the potential of this species for its use in the remediation of the study area. (C) 2017 American Society of Civil Engineers.