Microbial Features Indicating the Recovery of Soil Ecosystem Strongly Affected by Mining and Ore Processing

Tailings-derived soils formed from waste materials produced during mineral processing often exhibit extremes of pH, low content of organic matter and limited nutrient availability. The success of site revitalization depends mostly on the ability to maintain natural soil functions. We analyzed technogenic sediments from four selected localities in Slovakia defined as environmental burdens: Slovinky (SLS, SLD), Markušovce (MAS, MAD), Lintich (LIS, LID), Horná Ves (HVS, HVD) in the presented research. None of these sites has long been used for its original purpose. In all localities, the concentrations of several risk elements (As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Zn) still significantly exceed the statutory limit values. Besides the content of risk elements, the amounts of organic carbon, total nitrogen, pH value and moisture level in technogenic substrates were determined. We evaluated selected microbiological parameters, including microbial biomass carbon (MBC), microbial respiration and cellulolytic activity to determine how soil organisms tolerate long-term pollution. In general, the values of microbiological parameters were not as low as one would expect. The results confirmed a negative correlation between MBC content and concentrations of several toxic metals (Co, Cr, Cu, Ni, Zn). The values of assessed microbial indicators were in several cases comparable to those in natural soils. We noticed the lowest metabolic quotient values (qCO₂) in the heavily polluted locality HVS. The microbial quotient (qMic) was low in every locality except HVS, where the substrate availability index (SAI) was highest. The soil microbial community properties have shown that, despite adverse conditions, these emerging soils allow the growth and development of microorganisms to such an extent that they can adequately use available (although limited) nutrients. The data obtained suggest that these severely impacted soil ecosystems can restore their original environmental functions in time.