Background: Among a range of xenobiotics, that are introduced into the environment, especially dangerous are petroleum substances. Microorganisms participating in their decomposition, may be a good effectiveness indicator of biodegradation process.
Objective: The aim of this study was to determine the influence of soil contamination with diesel oil for changes in number of basic taxonomic groups of microorganisms, including bacteria, actinomycetes and fungi.
Material and method: The study was carried out in two soils, loamy sand and sandy clay, which, apart from granulometric composition also differed in organic matter content. Two levels of diesel contamination was used: 5% and 15% w/w of soil d.m. The soil samples, not contaminated with diesel oil, was left as a experience control objects. The number of microorganisms were evaluated by automated method with measuring impedance in media, using the analyzer BacTrac 4100.
Results: In the studied soils the largest group of microorganisms were bacteria, significantly less was fungi and actinomycetes. Based on the results of research it was found a significant effect on the quantitative composition of microflora was both contamination dose and type of soil. Diesel fuel at a concentration of 5% stimulated the number of bacteria and fungi in sandy soil. In general, increase in concentration of pollutants adversely affect the microorganisms, especially in loamy soils. Soil contamination with diesel oil resulted in a reduction in the degree of microbial growth rate (55% in loamy sand and 39% in sandy clay), and thus have an impact on their fertility. The reduction of SR index was correlated with increasing dose of pollutants.
Conclusions: Diesel oil affect the biological balance of soil and stimulates or reduces the number of different groups of microorganisms, depending on the amount of fuel. The presence of fuel decrease index of soil fertility, proportion to increase in the level of contamination.