Culture methods as indicators of the biological quality of phytostabilized heavy metal-contaminated soil

The short-term effect of aided phytostabilization of heavy metalcontaminated soil on microorganisms under outdoor field conditions was tested. Heavy metal contaminated soil from a mining site was amended with lignite, lime and two commercial fertilizers and vegetated with grass Festuca arundinacea. Results demonstrated that the amended phytostabilization approach of Pb-Cd contaminated soil gave a positive change on the native microbial populations evaluated by culturable techniques during the first 28 weeks of the experimental period. In the end of the experiment, the number of bacteria, actinomycetes and fungi increased in treated soil about 16-fold, 10-fold and 2-fold, respectively. Changes in the biodiversity of bacterial populations were evaluated by the Ecophysiological Index (EP) and the Colony Development Index (CD) for oligotrophs and copiotrophs. During the experimental period slower growing microorganisms (K-strategists) predominated. The application of amendments to the soil led to an increase of the CD index in both copiotroph and oligotroph populations after 28 weeks. EP, CD, bacteria, actinomycetes and fungi increased in the treated soil. Traditional microbiological methods based on culture techniques can be used to evaluate the biological quality of the phytostabilized heavy metal-contaminated soil.