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Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it asBacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium. [ABSTRACT FROM AUTHOR]

Sand storms have become a growing global environmental issue and there is an urgent need to explore cost-effective green technologies to stabilize the sands of desert regions. In this study, the performance of a ureolyticBacillussp. for stabilization of sands was evaluated. TheBacillussp. could efficiently consolidate sand particles by hydrolysis of urea and the subsequent production of calcite and aragonite minerals. The biostabilized sands had a high resistance to erosion by a 33 m s−1wind speed even after 12-d exposure to freeze-thaw cycles. The compressive strength of biostabilized sands was dependent on the applied cell density and concentrations of Ca2+and urea. High cell densities, urea and Ca2+concentrations reduced the compressive strength. The optimal cell density, Ca2+and urea concentrations were OD6000.4, 15 mM and 20 g L−1, respectively, when performance and cost were considered. This study shows that biostabilization of sand based on microbially induced carbonate precipitation (MICP) has potential for the prevention of sand storms and wind erosion of soil. [ABSTRACT FROM AUTHOR]