Soil biological activities in monitoring the bioremediation of diesel oil-contaminated soil

The effects of two different biological treatments on hydrocarbon degradation and on soil biological activities were determined during a 100-d incubation period. An evaluation of soil biological activities as a monitoring instrument for the decontamination process of diesel-oil contaminated soil was made using measurements of organic carbon content, soil microbial respiration, soil ATP and dehydrogenase, beta-glucosidase, lipase enzyme activities. Five samples were used: S (control, uncontaminated soil), CS (contaminated soil), SCS (sterilized contaminated soil), CFS (contaminated soil plus N and P), CCS (contaminated soil plus compost). The relationships between soil parameters and the levels of total petroleum hydrocarbons (TPH) residues were investigated. Results showed that inorganic nutrients NP and compost stimulated hydrocarbon biodegradation but not all biological activities to a significant extent. The residual hydrocarbon trend was positively related with that of the organic C content, microbial respiration and with beta-glucosydase activity, while both soil lipase and dehydrogenase activities were negatively related with the hydrocarbon trend. Lipase activity was found to be the most useful parameter for testing hydrocarbon degradation in soil.