Revegetation of waste fly ash lagoons. I. Plant selection and surface amelioration

Abstract

Glasshouse and field trials were conducted to select plant species suitable for revegetation of waste fly ash lagoons. Species which demonstrated potential for growth on fly ash or ameliorated fly ash in glasshouse trials were subsequently tested by direct seeding in situ at the Port Augusta power station in South Australia. Xero- and halophytes from the families Aizoaceae, Chenopodiaceae and Zygophyllaceae performed optimally in both sets of trials, and species most suited for revegetation and regeneration included Mesembryanthemum aitonis, M. nodiflorum, Atriplex holocarpa, A. lindleyi, A. vesicaria, Enchylaena tomentosa, Halosarcia halocnemoides, H. pergranulata, Scaevola collaris and Nitraria billardierei. A range of surface amelioration treatments for fly ash lagoons designed to overcome the chemical and physical limitations of fly ash to plant growth, and to reduce the effects of high temperatures, strong winds and low rainfall in the region were also tested. A 50-100-mm surface cover (overlay) of either local sandy topsoil or compost, stabilized with coarse organic mulch, hydromulch or erosion control fabric supported good germination and plant growth. The soil or compost overlay provided a seed bed for initial germination away from the toxic elements of the ash, while the stabilization treatment prevented wind-blown removal of both seed and seed bed, while also conferring some protection to germinating seedlings.