Date of Award

1998

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Communication, Health and Science

First Advisor

Dr Ian Bennett

Second Advisor

Dr Mary Boyce

Abstract

Industrial activities and natural occurrences of mineral ores can both result in the presence of high concentrations of heavy metals in the soil. These toxic metals have been shown to adversely affect human health and the environment. Currently, three main technologies are being used to solve this problem of soil contamination. These are incineration, landfill construction and physico-chemical treatments. The economic and environmental costs of each of these technologies tend to outweigh the merits of their application, especially where contaminated areas are small. These techniques do not necessarily remove the heavy metals from the soil, and can also inhibit biological activity by affecting the physical structure of the treated medium. Recent research has seen the development of alternative methods, which utilise living systems, for less expensive land rehabilitation. Phytoremediation is the process of utilising plants with some tolerance of soil contamination to rehabilitate polluted sites. One category of such plants comprises species that are able to accumulate high concentrations of heavy metals. Experiments carried out with herbaceous species (e.g. Alyssum tenium and Brassica juncea L.) and trees (e.g. Populus spp.) have presented valuable and successful reports regarding their application. The capacity of native Australian plants to fulfil these requirements is relatively unknown. Many species of Australian native flora are well adapted to the adverse conditions of arid and semi arid landscapes. Some are currently being utilised in the reclamation of such soils (Marcar & Termaat, 1990). Research with tree species in particular have seen the successful rehabilitation of saline and waterlogged soils. The economic values of these plants provide substantial incentive for their use in these applications. This study was aimed at initiating the development of research into the prospects of utilising Australian plants to carry out the phytoremediation of heavy metal-contaminated soil. Species from three families were selected for this study. These were Eucalyptus camaldulensis, E. lesouifii and E. globulus from the Myrtaceae family, Acacia heteroclita, A. saligna and A. quadramarginea from the Mimosaceae family and Casuarina obesa and Allocasuarina verticilatta from the Casuarinaceae family. Experiments were carried out to detennine the potential of these selected plants for the accumulation of lead. Seedlings of these species were subjected to lead treatments in both hydroponic and soil experiments. The quantity of accumulated lead in leaf, stem and root tissue of seedlings grown in varying lead concentrations was measured. The results obtained for species subjected to hydroponics experimentation was shown to correspond to results obtained for the same species in soil experiments. The results also showed that there were variations in physiological responses and levels of lead accumulated within tissues for each individual species. A. heteroclita accumulated the highest levels of lead in its tissues and showed mild toxic symptoms.

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