The relationships between indices of chemical soil pollution and the state of the microbiome of urban soils in transport, transport–industrial, and recreational zones of the city of Bishkek, as well as in the Ala-Archa Natural Park have been assessed. Using a DELTA X-ray fluorescence spectrometer, the total contents of Pb, As, Zn, Cu, Co, Mn, Cr, Cd, Hg, and Sb in the soils of the studied zones have been analized. The degree of contamination of the studied soils with heavy metals has been shown to depend on the traffic load and emissions from the thermoelectric power station. The functional diversity of soil microbiomes has been determined by multisubstrate testing, and the functional activity has been chromatographically assessed by carbon dioxide emissions. The health and stability of the microbial community have been evaluated using the shape coefficient of rank distribution of the substrate consumption rates (d), which serves as a measure of destabilization of the microbial system. A specific state of the soil microbiome characterized by a reduced number of consumed substrates, decreased metabolic activity, and destabilization of the microbial community has been revealed in the western part of the city. The studied heavy metals have been divided into groups by PCA depending on their effects on such biotic indices as microbial respiration and soil substrate consumption. The As–Pb–Cu–Co group is more strongly associated with the integrated indices of total heavy metal pollution (Zst) and most significantly inibited the substrate-induced respiration and consumption of pentose monosaccharides. The Hg–Cr–Mn group provides the most strong suppression of the consumption of amino acids and organic acids. The Cd–Zn–Sb group reduces the intensity of basal respiration and slightly increases the consumption of oligosaccharides and the entropy indices (Hk and χ2) of substrate consumption spectra. The use of the total heavy metal pollution index does not allow identification of a direct specific effect of heavy metal contamination on the soil microbiome, since in this study it did not show significant correlations with any of the investigated biotic indices. A conclusion is made that only the combined consideration of abiotic (chemical contamination) and biotic (microbiome responses) criteria should be taken into account when assessing the ecological risk of negative impacts on soils.
Aidyralieva et al. (Wed,) studied this question.