Assessment of the content of heavy metals and potential pathogenic microorganisms in soil under illegal dumping sites

The aim of the study was the assessment of the environmental contamination of soil by heavy metals and microorganisms within the uncontrolled landfill dumps and the impact of anthropogenic sources on the activity of selected soil surface horizons. Some physicochemical properties were determined according to commonly used procedures in soil science laboratories. The total of heavy metals concentration was assessed according to Crock and Severson and forms available according to Lindsay and Norvell. The total contents and mobile forms were determined by atomic absorption spectrophotometry. As part of the microbiological tests, potentially pathogenic evidence of bacteria was found indicating fecal contamination of the soil (E. coli and other coliform bacilli, Salmonella spp., and Enterococcus spp.). Quantitative analyses were carried out based on the calculation of the most probable number of microorganisms (MPN method). The activity of selected redox and hydrolases enzymes: the activity of dehydrogenases with the Thalmann method, catalase with the Johnson and Temple method, alkaline and acid phosphatase with the method of Tabatabai and Bremner. It was concluded that depending on the composition of the dump, the physicochemical properties of the soil were changed, too. Uncontrolled landfills significantly affected the increase or decrease in the pH of the tested soil and the organic content of the tested soil. The waste stored at the site affected the contamination of the soil by heavy metals to varying degrees. The results show that the most dangerous bacteria exist in the soil under the C landfill and this is where the greatest risk of soil contamination exists. The highest amount of selected enzymes activity was observed in soils under illegal C dumping sites. In the soil sourced from A and B landfills, the enzyme inhibition occurred which was linked to the lowering of the organic carbon. The results of the principal component analysis demonstrated that the content of heavy metals and the activity of enzymes are the indicators of anthropogenic pollution, whereas granulometric composition (sand and silt) is mainly associated with the natural environment.