Microbiological indicators and heavy metal concentration in ecological assessment of urban soils of Saint Petersburg, Russia

Abstract

This paper aimed to characterize urbostratozems (Urbic Technosol, WRB) of Saint Petersburg located in industrial (“Electrodepo” railway station) and residential (region Polish Garden) zones. These soils were also compared with background (natural) soddy podzol soil (Umbric Albic Gleic Podzol, WRB) sampled in recreational zone (suburban park “Oranienbaum”). Soil samples were collected from soil horizons for chemical analysis and from top of soils for microbialogical analysis in June of 2012. Chemical properties (pH, total organic carbon, mobile forms of K and P) and content of heavy metals (Pb, Cu, Zn, Ni) in soils were determined. Culturable forms of microorganisms (bacteria and fungi) were studied. Assessment of the enzymatic activity of the soil was carried out by culturing of microorganisms-producers of protease, amylase, cellulase and lipase on special media. Biotesting using cress (Lepidium sativum L.) seeds had been carried out for assessment of soil phytotoxicity. It was found that chemical properties of urban and natural soils differ greatly. Heavy metal pollution was evident in both urban soils, but maximum concentrations of heavy metals were found in the soil of the industrial zone. Phytotoxocity had been also most pronouncend in the soil of the industrial zone. The natural soil exhibited significantly higher respiration activity than urbostratozems. The greatest difference in the structure of the bacterial and fungal communities was observed between the natural soil of the recreational zone and the urbostratozem of the industrial zone. Algae had been present in the urban soils of the residential zone that was not observed in the natural podzol. The minimum number of producers of all enzymes, except for cellulase, was observed in the soddy podzol in the recreational zone. The maximum number of protease and amylase producers was found in the soil of the industrial zone. Lipolytic activity was almost the same in all samples. It was found that more sensitive biological methods are needed for environmental assessment of urban soils. The results of the article can be used by soil scientists and environmental engineers for a comprehensive environmental assessment of the condition of urban soils and for creating new urban green spaces.

Keywords

• urban soil
• heavy metal
• microbiological indicator
• enzyme activity
• soil phytotoxocity