Technogenic soils (Technosols) developed from mine spoils containing Fe sulphides: Microbiological activity as an indicator of soil development following land reclamation

Restoration of ecological functions by reclamation of post-mining areas stimulates soil-formation processes and initiates biological activity on the surfaces of disposal sites. The purpose of this investigation was to study the relationships between soil properties, microbiological activity and diversity in Technosols 45 years following land reclamation. The study area was located in the vicinity of the former Fe sulphide and uranium mine in Rudki village (Holy Cross Mts., Poland). The soils developed from tailings containing Fe sulphides (profile R1 and R2) and Fe sulphide and dolomite-bearing post-flotation sludge covered with loamy material (profile R3) were studied. Soil properties and enzyme (dehydrogenase, arylsulphatase, beta-glucosidase, urease) activities, respiration activity (RA) and total microbial counts (TMC) were determined, as well as molecular analyses were performed. The most important soil properties influencing enzyme activities, RA and TMC were pH and soil salinity. Biological parameters were also dependent on TOC, TN, exchangeable K and available P contents. Enzyme activity, RA and TMC were significantly lower in strongly acidic and saline profile R1 than in profiles R2 and R3, which represent areas where land reclamation was successful. Moreover, a decrease of enzyme activities, RA and TMC were observed with increasing depth of soil profiles. The lower activity of arylsulphatase, beta-glucosidase and RA in A horizon of profile R3 in comparison with similar horizon in profile R2 may reflect the pollution of R3 topsoil by trace elements. Molecular analysis revealed that Bacillus genus predominate in the studied profiles. Soil properties (particularly pH) that are a repercussion of reclamation works seem to be the main variables conditioning biodiversity at the bacterial strains and species level. The obtained results indicated that enzyme activity, RA and TMC are sensitive indicators of microbiological activity and can be a measure in the assesment of soil biological activity following land reclamation.