Microbiological assessment of the state of urban soils of the oil and gas region on the example of the territory of Kogalym

Abstract

In the course of this work, the total numbers of heterotrophic microorganisms and the numbers of microbes participating in the nitrogen cycle (ammonifying, denitrifying, nitrifying and nitrogen-fixing ones) in urban and natural (background) soils of Kogalym were estimated. A relation between the obtained results with geochemical indicators was revealed. Our microbiological analysis showed the predominance of nitrogen-fixing microorganisms in urban soils (5.0×104 – 2.0×106 CFU/g of soil), which were on average 44 less than in natural soils. In the last ones the average number of denitrifying microorganisms was 7.0×104 CFU/g of soil, exceeding 1.3 times their number in urban soils. Based on the information obtained, microbial contents in the soils of Kogalym were established as a row: nitrogen fixators > ammonifiers > heterotrophs > denitrifiers; in background samples: denitrifiers > ammonifiers > heterotrophs > nitrogen fixators. According to the data of ecological and geochemical analysis, an excess of the MPC of mobile forms of heavy metals, such as Cu, Ni and Zn, was revealed in the Eastern Industrial zone of the city. A significant inverse correlation was revealed between the number of denitrifying microorganisms in the Kogalym soil microbiocenoses and the content of mobile Ni and Cu forms, which points to a possible negative effect of these metals on the development of denitrifiers. The minimum number of ammonifying, denitrifying and nitrogen-fixing microorganisms was found in the Eastern Industrial zone, especially in the soil samples that were taken near the railway. On the whole, the absence of noticeable differences in the microorganisms` content of the studied groups in urban and natural soils indicates a low level of soil pollution in Kogalym. The obtained results represent the basis for subsequent ecological monitoring of the soils in the city and adjacent oil-producing areas, forecasting the environmental consequences of anthropogenic activities in these territories.