Abstract
ABSTRACT: Areas affected by coal mining can be recovered by revegetation with leguminous plants associated with nitrogen-fixing bacteria. This study addressed the isolation and characterization of native nitrogen-fixing bacteria from coalmine wasteland under different vegetation restoration approaches using Macroptilium atropurpureum (DC) Urb and Vicia sativa L. as trap plants. The bacteria were characterized and identified on the basis of 16S rRNA sequences. Additionally, nitrogen-fixing strains were characterized for tolerance to high heavy metal and low pH levels, as well as [...]
Highlights
Coal provides two-thirds of the non-renewable energy resources in Brazil and reserves are 20 and 75 times higher than those of oil and natural gas, respectively
Strains were obtained from all areas, but the soil with the longest restoration period (20 years re-vegetated with Acacia mearnsii + Eucalyptus sp.) had the highest number of strains
Most of the 115 nitrogen-fixing bacteria isolated from the coal mining areas are tolerant to very acidic pH (4.0), with few tolerating extremely acidic pH levels (3.0)
Summary
Coal provides two-thirds of the non-renewable energy resources in Brazil and reserves are 20 and 75 times higher than those of oil and natural gas, respectively. A total of 847.5 billion tons of coal is enough to maintain the current output for 130 years (Aneel, 2008). In Brazil, the major coal reserves are located in the region of Candiota, in the state of Rio Grande do Sul, with an estimated reserve of one billion tons, which can be extracted by open-cast mining down to a depth of 50 m (Stumpf et al, 2016). During mining and coal processing, a significant amount of sterile solid waste and sulfiderich (pyrite, marcasite, esfarelita, arseno-pyrite, galena, and chalcopyrite) tailings are produced. Due to AMD, dissolute minerals increase the solubility of some metals (As, Cd, Cu, Ni, Pb, Zn, Al, Cr, Mn, Mg etc) (Fungaro and Izidoro, 2006). As a result of this process, the contamination risk of surface and groundwater as well as of the soil increases, and the restoration of these areas become more expensive
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