Functional diversity of microorganisms in metal- and alkali-contaminated soils of Central and North-eastern Slovakia

A field-based study and laboratory tests were undertaken to determine the functional diversity of microorganisms in metal- and alkali-contaminated soils in Central and North-eastern Slovakia where iron ore and magnesite have been mined and processed for a long time. To improve the understanding of the functional diversity of microorganisms, we examined the effects of environmental factors on the functional diversity of microorganisms in metal- and alkali-contaminated soils in the emission field of heaps and tailings impoundments of iron ore mines (Central SpiĹĄ) and magnesite factories (JelĹĄava and LubenĂ­k). Biolog® Eco Plates were used to determine and assess metabolic profiles of microbial communities. The examined area of Central SpiĹĄ showed extremely high values of Hg and Cu and the values of Zn, Cd, Pb and Cr exceeding the permissible limit were determined. Soil reaction was extremely acidic to strongly acidic. The JelĹĄava and LubenĂ­k area was characterized by alkaline contamination and the soil reaction was slightly acidic to strongly alkaline. The values of Cr, Mn, and Mg exceeding the permissible limit were measured there. The results indicate harmful and even toxic contamination. Our results showed that the diversity of microorganisms was different in the investigated areas and it was significantly influenced by environmental factors such as soil reaction, bulk density, porosity, and heavy metals Hg, Pb, Cr, Zn, Cu, Mn and Mg. Based on the results of the Shannon index, we can conclude that the diversity was low to moderate (2.5-3.3) and medium (3.3-4.0). Correlations between functional diversity of microorganisms and soil reaction, Hg, Cr, and Cu were determined. Our findings are decisive for understanding the microbial diversity in metal- and alkali-contaminated soils and they can be used to assess the quality and health of soil, as well as for scientific applications of remediation techniques.