Biological properties of extremely acidic cyanide-laced mining waste

With respect to acidic, cyanide-laced tailings, the data about in situ toxicity and biological activity in highly polluted environment are often lacking. The aim of this study was to assess the microbial characteristics, composition of oribatid mite species, and level of genotoxic impact on plants in the area of inactive tailings pond (Horná Ves, Kremnica region). Sampling of the tailings, soils and selected plant species was carried out in spring of 2012. Trace element analysis (inductively coupled plasma emission and mass spectrometry) showed that concentration of Pb, Zn, and Cu in the tailings is approximately in thousands of ppm (mg kg(-1)). Amount of lead exceeded 16,000 mg kg(-1), which is perceived as the biggest threat with respect to possible toxicity. The risk is accentuated by extremely acidic pH of the tailings material which approached 2. In such conditions great mobility of (divalent) heavy metal cations is expected. The total cyanide concentration in the tailings was 472 mg kg(-1). Results of performed tests and measurements suggest that microbial activity at the tailings site (and its close environment) is hampered markedly. In the sludge material we detected low abundance of soil bacteria (2.08 × 10(4) CFU) and predominance of slowly growing K-strategists. On the other hand, the content of microbial C in the sludge sample was not too low, considering its extreme acidity and high amount of risk elements. In the same sample, just one mite species, Oppiella (O.) uliginosa (Willmann 1919), was identified. Also in case of the dam site the abundance of mites was considerably lower in comparison to reference sample. Values of Oribatida abundance were in positive correlation with values of microbial biomass carbon. Results of the pollen grain abortivity test, applied in situ on chosen plant species, indicated substantial presence of genotoxicity in the environment. Total induction index of tailings pond reached 3.59(±2.4) which expresses also total load of locality, comparing to natural biotope. In case of the technogenic sediment, the value was more than three times higher.