Selection of tree species as assets for mine phytoremediation using the genus Rhus {Anacardiaceae) as a model

摘要

Gold and uranium mining operations commenced in the late 1800s in the Witwatersrand Basin gold fields of South Africa, and have resulted in the accumulation of substantial amounts of tailings and other mine residues. Mine tailings storage facilities (TSF) and degraded lands associated with mining are of concern, and require appropriate vegetation to reduce their environmental impact and achieve closure objectives. Previous studies in South Africa have culminated in the selection of plant species adapted to various mine environments, and the establishment of a series of long-term trials for phytoremediation and phytostabilisation of gold TSF and polluted substrata. Included are trees for the hydraulic control of acid mine drainage (AMD) from TSF, and, in some cases, direct extraction of contaminants from shallow groundwater (the mine woodlands project trials). In addition to mitigation of pollution, an objective is to determine the potential for secondary industries and sustainable land-use based on 'phytoremediation plant products'. These products includephytochemicals as pharmaceuticals. Plant flavonoids, with the ability to scavenge free radicals, have potential commercial value. Results of preliminary investigations on the presence of phenolic compounds in Rhus lancea (Anacardiaceae) trees, planted in the mine woodlands project trials on AMD are reported. The relationship between contamination of the soil and the production of secondary metabolites is emphasised by using chemometric methods. Since ecotypes of R. lancea that are tolerant to contamination have already been identified, the benefit of evaluating and ultimately integrating the planting of such trees into the mine rehabilitation programme is evident. Quantitative analyses of useful phenolic compounds identified can be used to indicate if the trees are a potentially sustainable source of secondary metabolites. All extracts of both mine and natural populations were found to contain large amounts of soluble phenolic compounds, gallic acid and anthocyanidin derivatives. This study demonstrates the possible use of plants in general, and Rhus lancea in particular, as a foundation for industries based on renewable natural resources in mining communities.