Abstract
The soil in the Sangan iron-mining region in the east of Iran is contaminated with a high concentration of heavy metals, especially iron. The release of these pollutants into environment results in the transfer and accumulation of iron through the food chains, hence a reasonable solution is required to restore it. Bioaugmentation is an environmental friendly option to reduce the hazard effects of heavy metal in the contaminated soil. In this study, the consortia of two indigenous cyanobacteria isolated from soil of Sangan iron mining and used to bioremediate soil contaminated with iron, chromium, copper, lead, and nickel. The experiments were carried out by three treatment methods, including control soil, surface soil sprayed with cyanobacteria, and soil mixed with cyanobacteria for six months under laboratory condition. The scanning electron microscope showed the development of a network of filaments of the inoculated cyanobacteria (Oscillatoria sp. and Leptolyngbya sp.) with soil particles in both treatments. Bio-augmentation of the soil increased initial nitrogen content from 406 mg/kg in control to 664 mg/kg in soil mixed with cyanobacteria and 710 mg/kg in soil sprayed with cyanobacteria. Cyanobacteria inoculation decreased the available concentration of lead and nickel. The non-available heavy metal of soil in sample sprayed with cyanobacteria was in decreasing order: Cr > Fe > Ni > As > Pb > Cu. The maximum metal removal efficiency was 32%. In soil mixed with cyanobacteria increased in the root and hypocotyl lengths of radish and lettuce was observed compared to that in the control soil, indicated in the improvement of soil quality after bioremediation.
Highlights
Soil contamination with heavy metals is a global problem that poses a severe threat to ecological health, human health, and safe food production
Morphology of cyanobacteria The morphology of cyanobacteria isolated from the soil samples collected from Sangan iron ore mine (SIOM) and cultured in BG-11 was characterized based on their microscopic features
Two cyanobacteria species were recovered from the soil, which was identified as Oscillatoria sp. and Leptolyngbya sp. (Figure 2)
Summary
Soil contamination with heavy metals is a global problem that poses a severe threat to ecological health, human health, and safe food production. Nisha et al [31] investigated the effect of the inoculation of two indigenous heterocystous cyanobacteria (Nostoc ellipsosporum HH-205 and Nostoc punctiforme HH-206) on salty soil They found that the indigenous cyanobacterial species enhanced the productivity of soil and they are useful option for remediation [32] examined the impacts of cyanobacterial inoculation on dryland soil restoration. Its indigenous strains of cyanobacteria are isolated, cultured, and introduced to polluted soil to remediate it From this primary goal, three specific objectives were derived: (1) determination of soil organic carbon and nitrogen content before and after bio-augmentation treatment; (2) Evaluation of the removal efficiency of heavy metals from contaminated soil by cyanobacteria inoculation; and (3) investigation on bioremediation efficacy by planting
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