Methodological Approaches toward Chemico-Biological Diagnostics of the State of Soils in Technogenically Transformed Territories

The comprehensive diagnostics of the state of soils in the impact zone of thermal power station (TPS-5) in the city of Kirov was performed on the basis of the soil chemical analyses and the study of biota response to the loads at different organization levels. The chemical analyses attested to a satisfactory state of the soils. However, the use of soil cyanobacteria and bird’s-foot trefoil (Lótus corniculátus) as test objects showed the toxicity of studied soil samples. The toxicity of the samples was judged from the bioindication effects of cyanophytization and melanization of soil microbial complexes. The obtained results demonstrated that at relatively low concentrations of total and mobile heavy metal compounds in the soil samples, their amount released into the tested soil water (1: 4) extract exceeded the limit allowable for normal functioning of living organisms. For the first time, the express cyanobacterial tetrazole-topographic method of biotesting was applied in the geoecological study to estimate the toxicity of the soil samples. The results obtained with the help of traditional and express methods proved to be comparable. The express-method was sufficiently sensitive and efficient. It allowed the determination of the samples' toxicity in five hours, i.e., four to five times faster than the traditional technique. An inverse relationship between the number of viable cells of cyanobacteria (as judged from the inclusion of formazan crystals) and the concentration of lead ions in the tested soil extracts was found. This finding can be considered a prerequisite for further study and application of the express method in the practice of geoecological monitoring. Our study demonstrated the necessity of a comprehensive approach for the assessment of the real ecological state of soils in the investigated impact zone of the thermal power station.