Geobotany And Biogeochemistry In Mineral Exploration PdfBy Alexander C. In and pdf 11.05.2021 at 06:15 6 min read
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Parque Antonio Rabat , Santiago, Chile; e-mail: rginocc cimm. However, few metal-tolerant and metal hyperaccumulator plants have been reported in the region in comparison with other areas of the world.
This may be largely explained by the scarcity of scientific studies of the native vegetation growing on natural mineralized or metal-contaminated areas and the unfrequent use of biogeochemical prospecting techniques by the local mining industry, rather than the proven absence of these plants. Latin America is, however, an area where metal-tolerant and hyperaccumulator plants metallophytes should be found, not only because of the wealth of ore deposits and associated metal polluted areas, but also due to its high and unique plant diversity.
Key words: hyperaccumulators, metal-tolerant plants, biodiversity, metal ores, biogeochemistry. There is a group of plants, however, called metallophytes that dominate on mineralized areas, either natural e. Metal tolerance in higher plants has been traditionally assessed through standardized laboratory tests by determining the effect of metal ions on root elongation e. Using this methodology, numerous studies have identified and quantified metal tolerance for copper, cadmium, iron, manganese, nickel, lead, and zinc in several higher plants e.
However, some metallophytes can accumulate very high concentrations of metallic or metalloid elements in their aerial tissues, to levels far in excess of normal physiological requirements and far in excess of the levels found in most plant species, even those tolerant of metalliferous soils Table 1. Indeed, some of these plants can not complete their life cycles when grown on normal soils. Metallophytes may have very restricted geographical distributions and thus can correspond to rare species Reeves They are often endemic to few small areas of metalliferous soils; some are known from only a single site or have been collected in only few occasions e.
Others, however, are species strictly restricted to their particular metallogenic provinces, such as some Becium species, that only grow on isolated natural copper outcrops in the Democratic Republic of Congo formerly Zaire , central Africa Brooks et al.
Hyperaccumulator plants represent a low percentage of all angiosperms less than 0. Therefore, they are rare in the Plant Kingdom. The phenomenon has thus evolved several times in widely different plant groups under the same environmental stresses.
Their metal-specific adaptations and large diversity in terms of species, families and life-forms, grant metallophytes a special place in issues related to biodiversity and genetic resources conservation. Although the European taxa are well known, tropical and sub-tropical metallophyte taxonomy and ecology lie far behind despite the ever-increasing mining activity taking place in these latitudes.
First, the restricted distribution of metallophytes to metalliferous soils has brought about a negative interaction with the mining sector, since these plants grow where the metal ores occur and are extracted from the ground.
Although the mining sector is not necessarily the most important influence on plant diversity in a particular region, mining does almost always have an impact on biodiversity and, in some cases, the effects can be huge and irreversible, even in industrialized countries with developed environmental regulations MMSD Indeed, opencast mine operantions results in total clearance of vegetation and topsoil over large surfaces, and although new and good-managed operations make provisions for rehabilitation, such impacts are more far-reaching than those of the other sectors e.
The best practices for rehabilitation in the region have usually been the introduction of exotic species that have had many deleterous effects on native plants and ecosystems or the introduction of exotic species that have had better livelihood benefits, such as woody trees for fuel, timber, or food for cattle. In some cases, introduction of native species that are able to survive in the mined environment has happened, but these programs have mainly considered the specific identity of plants and not their metal tolerance and accumulation status.
Second, metallophytes endemic to areas of well-defined soil composition have been used historically as geobotanical indicators for mineral exploration. For instance, some of these plants have extensively been used in Europe and central Africa as metal bioindicators as they can be used to delineate metalliferous substrates when prospecting for metal ores Brooks Third, further uses for metallophytes by the mining industry have been promoted in the most recent drive towards sustainable development and responsible mine site closure in Europe and North America Whiting et al.
On the one hand, endemic metallophytes can be used in the revegetation and restoration of former mined sites phytostabilization , and on the other, they can be used in the clean-up of toxic metals from soils phytoextraction or in the phytomining of low grade ore that cannot be processed economically by other techniques Baker et al.
The deposition of metal-rich wastes in terrestrial environments by the metal mining industry e. Abandoned and naturally recolonized old mine sites can therefore be seen not only as a liability but also a resource base of unique genetic materials.
The study of these plants and their colonization behaviour and evolution observable on former mine sites has improved closure and rehabititation strategies in some mined areas of developed countries e. Brooks noted that in comparison with North America, Oceania, Asia, Europe and Africa, the biogeochemical data available for mine sites in Latin America was very few.
However, this may be better explained by the scarcity of both scientific studies on native vegetation growing on natural mineralized or metal-contaminated areas and biogeochemical prospecting with plants, rather than the proven absence of these plants in the Region.
Information on metallophytes in Latin America has been derived from two main sources: scientific research performed by botanists and plant ecologists and geobotanical surveys performed by geologists and mining engineers. Scientific research on metallophytes has been scarce in the region; plant species have been described in the literature as either metal tolerant 30 species or hyperaccumulators species; Figure 1 and Table 3 , a low number when compared to the high diversity of plant species present in the Region Cincotta et al.
It is clear then that from all the rich plant biodiversity present in Latin America only few species have been reported as metallophytes and investigations have been concentrated on ultramafic soils of few countries. Large-scale mining in Latin America has used traditional methods of exploration for minerals based on geology e. It is not suprising therefore that geobotanical surveys of the region are rarely reported in the literature see Table 4.
However, geobotanical surveys may have been performed by some mining companies during the course of mineral exploration but the results may be hidden in confidential reports and thus are not available for the public domain.
One of the few geobotanical surveys published in the region are those of Viladevall et al. Viladevall et al. Although these plants cannot be classified as hyperaccumulator plants since they achieve a maximum of ppb of Au and ppm of Sb in their leaves, they may be considered as metallophytes. They reported that all the shrubs studied had the same pattern of metal accumulation in above-ground structures, with the exception of Prosopis alba and P. It is interesting to note that the species described by Viladevall et al.
For example, B. Furthermore, F. Therefore, we may speculate that metal-tolerant ecotypes may have evolved on metal-rich soils in these other countries where they have not been described as indicators or metallophytes. Identification of metallophytes in Latin America seems to be increasing in the last decade, but numbers should further increase as the region has high potential for harbouring metal-tolerant and hyperaccumulator plants. This is not only due to the large number of ore deposits and metal-enriched areas such those found near abandoned tailings dumps and metal smelters distributed throughout the region, but also due to its high and unique plant diversity.
Latin America has major centers of plant diversity in comparison with other areas of the world. Indeed, eight of the twenty-five biodiversity hotspot areas so far defined in the world for their high biodiversity are located in Latin America Fig. Furthermore, the Mediterranean-type climate region and the winter rainfall deserts of Chile have recently been classified under the highest priority at the regional scale for biodiversity conservation of ecoregions of Latin America Arroyo et al.
However, all this high diversity is still poorly evaluated, studied, and protected, including that of potential and known metallophytes. Major tropical wilderness areas: A Upper Amazonia and Guyana.
New and strong investments in ore exploration and exploitation have been made both within the private and government sectors, assuring the future of the metal mining industry.
These regions are also coincident with hotspots for biodiversity Fig. Thus they are highly vulnerable to extinction if present and future mining is not adequately regulated.
The same situation may prevail for metallophytes with restricted distributional ranges. The lack of environmental regulations for the mine sector in most Latin American countries until recent decades resulted in severe threats to local vegetation in general and metallophytes in particular. Latin America has attracted the majority of the world's investments in mining, and therefore new laws and regulations alone may be not enough to prevent present and future threats to metallophytes that may be discovered in the region, due mainly to habitat loss.
Despite these problems, some progress by Latin American governments, mining industries and international actions to protect biodiversity such as the Convention on Biological Diversity is being made at policy, regulatory and technical levels.
Therefore, a major effort is required by local scientists, government agencies and mining companies to recognize and study metallophytes that may exist in Latin America. Extensive geobotanical exploration is needed not only on mineralized areas but also on abandoned tailings dumps or other metal-enriched areas. The risk is that they may be eliminated by mining activities before they have ever been identified.
However, there is a great potential for this particular group of plants in the region as plant biodiversity is high and unique and metal ores occur in abundance. Vigorous efforts must therefore be made in Latin America to locate metallophytes in their natural habitats and to afford them adequate protection. Metal mining has posed serious threats to plant diversity in the region, including known and to-be recognized metallophytes, and it will continue so if no special consideration is taken with this special group of plants.
Local plant extinctions can be caused by any sectorial activity, but metallophytes are likely to go extinc as a result of mining activity alone, as they grow on or near mining deposits. The obliteration of this special group of plants will result in the loss of a potentially valuable resource that can be used by the mine sector in best-practices for closure and rehabititation of mined sites, as they constitute a remarkable biological resource of great potential in the phytoremediation of metal-enriched soils and metal-rich wastes.
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Indicators for heavy metals in the terrestrial environment: VCH, Weinheim, Germany. In: Brooks RR ed Plants that hyperaccumulate heavy metals.
Their role in phytoremediation, microbiology, archaeology, mineral exploration and phytomining: CAB International, Oxon.
National Geographic Research and Exploration 6: National Geographic Research and Exploration 8: Intercept Ltd. Canadian Journal of Botany Springer-Verlag, Berlin, Germany. Journal of Cleaner Production From the Sudbury smelting area. New Phytologist Trends in Ecology and Evolution Acta Botanica Neerlandica Botanical Review Thesis, P.
Mining Environmental Management 6: 7- 9. Geochemistry: Exploration, Environment, Analysis 2: Progress in restoring the smelter-damaged landscape near Sudbury, Canada.
Geobotanical prospecting refers to prospecting based on indicator plants like metallophytes and the analysis of vegetation. For example, the Viscaria Mine in Sweden was named after the plant Silene suecica syn. Viscaria alpina that was used by prospecters to discover the ore deposits. A "most faithful" indicator plant is Ocimum centraliafricanum , the "copper plant" or "copper flower" formerly known as Becium homblei , found only on copper and nickel containing soils in central to southern Africa. In , Stephen E.
Parque Antonio Rabat , Santiago, Chile; e-mail: rginocc cimm. However, few metal-tolerant and metal hyperaccumulator plants have been reported in the region in comparison with other areas of the world. This may be largely explained by the scarcity of scientific studies of the native vegetation growing on natural mineralized or metal-contaminated areas and the unfrequent use of biogeochemical prospecting techniques by the local mining industry, rather than the proven absence of these plants. Latin America is, however, an area where metal-tolerant and hyperaccumulator plants metallophytes should be found, not only because of the wealth of ore deposits and associated metal polluted areas, but also due to its high and unique plant diversity. Key words: hyperaccumulators, metal-tolerant plants, biodiversity, metal ores, biogeochemistry. There is a group of plants, however, called metallophytes that dominate on mineralized areas, either natural e.
Botanical methods of prospecting involve the use of vegetation in searching for ore deposits. Although these methods have been used for several centuries, there is much confusion about terminology because there are two distinct methods of botanical prospecting. Geobotanical methods are visual and rely mainly on an interpretation of the plant cover to detect morphological changes or plant associations typical of certain types of geologic environments or of ore deposits within these environments. Biogeochemical methods see Biogeochemistry , which have been used only since the s, involve chemical analysis of the plant cover to detect mineralization. Geobotanical methods were first used in Roman times when vegetation was employed in the search for subterranean water. Later the Russian botanist Karpinsky became the first man to study thoroughly the relationship between plant communities and their geologic substrate. A number of books have appeared on the subject of geobotanical
Biogeochemistry in Mineral Exploration, Volume 9
Buerger, Alan Douglas Geobotanical, biogeochemical and geochemical studies in the mosaic of savanna types in southern Ngamiland, with special reference to their use in mineral exploration in calcrete and sand covered areas. A thesis written in four parts; part 1, the physical background of southern Ngamiland; part 2, geobotanical, geochemical and biogeochemical investigations in the Ngwakio pan area; part 3, geobotanical, geochemical and biogeochemical investigations in the Mawani area; part 4, conclusions and recommendations. The study in the Ngwako pan area was concentrated in the vicinity of known copper mineralization in Ghanzi series rocks to the north east of older Kgwebe series porphyries, sandstones and diabases. The results of geobotanical, geochemical and bio-geochemical investigations demonstrated the applicability of these methods to prospecting here.
Plant Function, Chemistry and Mineralogy 2. Field Guide 1: Climatic and Geographic Zones. Field Guide 2: Sample Selection and Collection 4. Sample Preparation and Decomposition 6.
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