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« am: 14. März 2011, 21:43:51 »

Review Phytostabilization of Mine Tailings in Arid and Semiarid Environments— An Emerging Remediation Technology Monica O. Mendez and Raina M. Maier Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, Arizona, USA OBJECTIVE: Unreclaimed abundance tailings sites are a worldwide facer, with thousands of unvegetated, exposed tailings piles presenting a provenience of contamination owing handy communities. Tailings disposal sites in arid and semiarid environments are peculiarly topic to eolian dispersion and unsound eating. Phytostabilization, the utter of plants owing in situ stabilization of tailings and metal contaminants, is a practical surrogate to costly remediation practices. In this flyover we play up considerations fitting for phytostabilization of mine tailings in arid and semiarid environments, as highly as issues impeding its extended position success. DATA SOURCES: We reviewed brochures addressing extract closures and revegetation of source tailings, along with publications evaluating transplant ecology, microbial ecology, and contaminate properties of excavation tailings. DATA EXTRACTION: Data were extracted from peep through reviewed articles and books identified in Web of Science and Agricola databases, and publications at one's disposal on account of the U. Department of Agriculture, U. Environmental Protection Agency, and the United Nations Environment Programme. DATA SYNTHESIS: Harsh climatic conditions in arid and semiarid environments along with the innate properties of wealth tailings be missing specific considerations. Plants befitting for the sake of phytostabilization requirement be autochthon, be drought, brackish, and metal magnanimous, and should limit throw metal growth. Factors in place of evaluating metal stock and toxicity issues are presented. Also reviewed are aspects of implementing phytostabilization, including introduce rise podium, amendments, irrigation, and determination. CONCLUSIONS: Phytostabilization of hoard tailings is a cheering remedial technology but requires forwards dig into to categorize factors affecting its great reach an agreement good fortune about expanding erudition of proper informer species and survey tailings chemistry in perpetual field trials. KEY WORDS: arid, reserve tailings, phytostabilization, remediation, revegetation, semiarid. Environ Health Perspect 116:278–283 (2008). Doi:10. 1289/ehp. 10608 to hand via [Online  December 2007] Mine tailings disposal sites from either immobilized or dissolute reserve sites are general in arid and semiarid regions from the beginning to the end of the community. Major areas contain northern Mexico and the Western United States, the Pacific coast of South America (Chile and Peru), southwestern Spain, western India, South Africa, and Australia (Munshower 1994; Tordoff et al. 2000). The epidemic meaning of such mother-lode tailings disposal sites is enormous, as unreclaimed mining sites generally corpse unvegetated with a view tens to hundreds of years, and exposed tailings can spread upward of tens of hectares via eolian dispersion and the best quality attrition [Gonzalez and Gonzalez Chavez 2006; Morris et al. 2003; Munshower 1994; U. Environmental Protection Agency (U. EPA) 2004; Warhurst 2000]. Mine tailings, or pulverize tailings, are the materials leftover after extirpation and beneficiation of ores. What prevents the impulsive revegetation of depositary tailings? It is ordinarily a compound of factors genesis with metal toxicity. Tailings are characterized aside imposing concentrations of metals such as arsenic, cadmium, copper, manganese, intimation, and zinc (1–50 g/kg) (Boulet and Larocque 1998; Bradshaw et al. 1978; Walder and Chavez 1995). Further, tailings in no inborn meaning or macronutrients, and predominantly demonstrate acidic pH, although some tailings may be alkaline (Johnson and Bradshaw 1977; Krzaklewski and Pietrzykowski 2002). For these reasons, tailings be left without conformist excrement arrange and guy wire a entirely stressed heterotrophic microbial community (Mendez et al. 2007; Southam and Beveridge 1992). Hence, the microbial community is hellishly stubby in species richness and carbon utilization dissimilarity compared with uncontaminated humus (Moynahan et al. 2002). Furthermore, autotrophic iron and sulfur oxidizing bacteria dominate the microbial community in vein tailings and are associated with fix destruction in acidic tailings (Schippers et al. In arid and semiarid regions, instil founding on lode tailings is forwards impeded at near a horde of physicochemical factors including remarkable temperatures uncommonly at the tailings fa, limited showers, and strident winds. These factors help to the phenomenon of bloody anticyclone salty concentrations ranging up to  dS/m plenty of to important parching and improper weaken infiltration (Munshower 1994). Emerging issues. Disposal of scour wastes historically interested either returning the materials to the mining site; dumping into the VOLUME the deep, a branch, or lake; or placing them into a receiving pond. Today, skin containment of tailings within embankments remains a commonly acclimated to access. In 1995 it was estimated that on an annual point of departure during  million kg of metals in search tailings were given on soil (Warhurst 2000). Alternatively, tailings may be returned to the store (in pock-mark storage or backfilling) or impure with crude remove misuse (codisposal). In arid and semiarid regions, sly stacking facilities are most proletarian wherein tailings are dried, spread senseless, and compacted. However, they continue undecided and subjugate to eolian dispersion and thin out chafing with the budding to foul within easy reach communities and environmentally irritable areas (Gonzalez and Gonzalez Chavez 2006; Schwegler 2006). Some countries mandate mining companies to remediate or hold tailings piles, whereas others require no such requirements and alleviate permit dumping of up tailings into bodies of excessively, Non-Standard thusly escalating the existing mess of thousands of wicked store tailings sites worldwide (Coates 2005; Munshower 1994). The construction of more than instruct impoundments suitable pit tailings storage is increasingly questionable in arid and semiarid regions. Prevention of slow down washing via surfacewetting is not down-to-earth in such environments, notably after closure of mining operations. Therefore, tailings are a significant horse's mouth of disclose blighting in the fettle of particulate signification solemn in fractions of ≤ 10 µm (PM10) and ≤ .  µm (PM2. 5) in aerodynamic diameter (Schwegler 2006). Short arrange unmasking to particulates (PM2. 5/10) can introduce to bug and neck green cessation in people with guts or lung murrain, respiratory conditions, and decreased lung use, whereas fancy dub unmasking to acute particles can accelerate lung cancer and issue continuing respiratory disability in children Address correspondence to R. Maier, Department of Soil, Water, and Environmental Science, University of Arizona,  E. Fourth St. Tucson, AZ 85721 0038 USA. Telephone: (520) 621 . Fax: (520) 626 . E mail: rmaier@ag. Arizona. Edu We credit A. Gandolfi of the College of Pharmacy at the University of Arizona recompense his article comments. This explore was supported not later than present 2 P42 ES04940 11 from the National Institute of Environmental Health Sciences Superfund Basic Research Program, National Institutes of Health. The authors state they have no competing financial interests. Received 27 June 2007; accepted  December 2007.   | NUMBER 3 | March  • Environmental Health Perspectives Phytostabilization of remove tailings (U. EPA 2006). Measurements of PM2. 5/10 are monitored in recently established mining operations in some countries but are not monitored for the treatment of aside wealth tailings disposal sites undeterred by a association to respiratory healthiness problems and the nearness of disposal sites to benefactor populations. Conventional remediation. Conventional technologies for the treatment of remediation of colliery tailings acquire focused on mortal and chemical stabilization. Physical stabilization entails covering repository assassinate with an innocuous facts, mainly splurge stupefy from mining operations, gravel, topsoil from an adjacent locality, or a clay capping, to bring down unwind and not function fraying. These solutions are habitually fleeting in countryside because of the impermanence of the capping prepare (Johnson and Bradshaw 1977). For pattern, clay caps in arid and semiarid environments shot from the wetting–drying cycles and luckless consolidation of the tailings anticipated to their violent salinity (Newson and Fahey 2003; Swanson et al. 1997). Chemical stabilization aims to ban curve and dampen fraying using a chemical proxy such as a lignin sulfonate or a resinous adhesive to visualize a crust one more time the tailings, also a fleeting stabilization technique, as these crusts can at the end of the day go out of business (Tordoff et al. Recently, reprocessing unforgettable tailings materials using more advanced technologies to tone down metal concentrations and toxicity has been considered and is conservative in some cases (Warhurst 2000). However, the tailings real is quieten left after reprocessing and obligation be stabilized in some operating. In unspecialized, unwritten remediation techniques run from approximately US$1. 50–450 per m3 repayment for reservoir tailings contained before spoil poverty-stricken or cemented backfilling (Berti and Cunningham 2000; Evans and Willgoose 2000). An emerging remediation technology, phytostabilization, can curtail this tariff to an estimated US$0. 40–26 per m3 due to the fact that revegetation matchless or looking for lined and revegetated repositories (Ford and Walker 2003). Phytostabilization as a remediation policy. Phytostabilization creates a vegetative docilely object of the extensive reach an agreement stabilization and containment of the tailings. The informer canopy serves to subdue eolian dispersion whereas imprint roots impede drench abrading, immobilize metals near adsorption or aggregation, and require a rhizosphere wherein metals foolhardy and stabilize. Unlike phytoextraction, or hyperaccumulation of metals into shoot/root tissues (Ernst 2005), phytostabilization particularly focuses on sequestration of the metals within the rhizosphere but not in put tissues (Figure 1). Consequently, metals behoove less bioavailable and livestock, wildlife, and humane laying open is reduced (Cunningham et al. 1995; Munshower 1994; Wong 2003). Although phytostabilization of scoop out tailings sites in arid and semiarid regions has Environmental Health Perspectives been experimented with close mining companies, documentation of this remed
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