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Phytoremediation and metal speciation in highway soils Padmavathiamma, Prabha Kumari

Abstract

Research was conducted to develop a cost effective and environmentally friendly technology to limit the dispersal of metal contaminants from highway traffic in the soil to the surrounding natural environment. The study comprised preliminary field measurements followed by two pot experiments and a field study. The first study evaluated the phytoextraction/ phytostabilisation potential of five plant species: Brassica napus L (rape), Helianthus annuus L. (sunflower), Lolium perenne L (perennial rye grass), Poa pratensis L (Kentucky blue grass) and Festuca rubra L (creeping red fescue) for metals (Cu, Mn, Pb and Zn), in soils with different metal contamination levels. The promising plant species identified were Lolium perenne, Festuca rubra and Poa pratensis. Total soil and plant metal concentrations, as well as the relative metal partitioning in different soil fractions and in plants were determined to provide an estimate of the mobility and potential bioavailability of metals in the soil. The second study evaluated the effectiveness of soil-plant-amendment interaction in immobilising metals in the soil. The amendments included lime, phosphate and compost individually and in combination, and were applied to the plant species: Lolium, Poa and Festuca. Maximum metal immobilisation was achieved in the soil by the combined application of amendments in conjunction with growth of Festuca for Cu, Poa for Pb and Zn and Lolium for Mn. The results obtained from first and second studies were confirmed by conducting field studies. A completely randomized factorial experiment in split plot design with three plant species (Lolium, Poa, and Festuca) individually and in combination, with and without soil amendments was conducted along Highway 17 soil in southwest British Columbia. The influence of root-soil interactions and seasonal influence on the solubility and bioavailability of metals in the soil with and without soil amendments was also evaluated. The best management practices (BMP) developed from the study have the applicability for phytostabilisation of metal contaminated sites and can be suggested as a risk management activity, reducing long-term associated risks.

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