Microbiota present in a mining waste, as an option for mine tailing dams restauration

Abstract

In Mexico, mining exploitation is a very important economic activity. Unfortunately, it generates large volumes of solid wastes (jales, from the Náhuatl word xalli, that means fine sands) that are disposed in mine tailing dams (presas de jales) and cover vast extensions of land, in which there is no vegetation. Mines are responsible for 65% of the industrial wastes produced in Mexico. The composition of the particulate matter from mine tailing dams varies depending on the existing mineral deposits. This study worked with tailings from a mine rich in iron pyrite in the State of Mexico, Mexico. The physicochemical characterization of the waste indicates that it is a compact particulate material without organic matter, with small water-retaining capacity and whose pH acidizes under atmospheric conditions (weather, biological and chemical phenomena or “weathering”). The lack of organic matter is crucial to explain the absence of any visible superficial microorganism growth in tailing samples to which water was added (and was not absorbed). The sowing of tailings in a series of liquid culture media indicated the presence of native biota, which under microscope observation showed different fungi and bacteria, which were tentatively identified through bioassays. Aspergillum nidulans, Helicosporium panacheum, Humicola alopallonella, Alternaria alternata and Cladobotryum mycophilum were isolated from the initial mixed cultures. Barr culture media showed the presence of sulfate-reducing anaerobic bacteria identified in the literature as Desulfovibrio desulfuricans. The decline of pH in the tailing, subject to weathering, indicates the presence of sulfur-oxidizing bacteria, assumption confirmed in the laboratory with the oxidation of the earth ion. It is, possibly, dueto Acidithiobacillus ferrooxidans. When fragments of tailing were put on a culture of Aspergillus nidulans (native biota) it was observed that there was fungi growth on the free surface of the wastes. These results observed in laboratory scale led to the assumption that it is feasible to achieve colonization of the tailings by filamentous fungi present as native biota, if there is addition of moisture and nutrient. It is necessary, however, to confirm this statement through bioassays in a larger scale.