Abstract

Since 1990, Almaty City’s soils has been considerably polluted by heavy metals, which resulted in its’ unhealthy ecological conditions. Almaty soils are light chestnut soils with the following physical and chemical properties: packing, 1.6±0.5 g∙cm^-3; available air space, 36.1 ± 9.4%; salt composition of the soil aqueous extract, 0.12±0.04%; hygroscopity (water-absorbing quality), 17.2±1.8, quantity of exchangeable cations, mg∙ eqv∙100^- g soil- 59.1±4.2 Ca²⁺, 8.4±0.5 Mg²⁺, 0.6±0.1 K⁺, 0.3±0.04 Na⁺; humus, 1.6±0.4%; С_total, 0.9±0.2%; N_total, 0.14±0.02. The purpose of this research was to determine the degree of soil toxicity by the method of multisubstrate testing (MST) for the integral studies of Almaty city soils’ bacterial communities, polluted by heavy metals (HM). This method measures soil bacterial communities’ activity in terms of its uptake intensity of 47 different organic substrates. Their stunted condition was determined through a decreased amount of consumed substrates (“N”) and urban soils’ metabolic activity decay: total biomass (“W”), load upon ecosystem or disturbance “d” coefficient. It was found that: “d” ecoefficient equaled 1.0 for the baseline soil and “d” ratio equaled 0.6 for urban soils. Ecological soil state was assessed using MST method, looking into soil bacterial communities’ activity in terms of its uptake intensity of different organic substrates. This method was developed in the last decade of the twentieth century for the purpose of investigation of soil microbial communities’ state. Thus, urban soil samples displayed worse uptake intensity than the baseline soil. Hence, the MST method may be used as the original method of evaluation of urban soil toxicity degree.

Key words: Biological control, multisubstrate testing, bacterial communities, heavy metals, urban soils.