Artificial changes in the properties of a soil contaminated with hexachlorobenzene were promoted in order to study the effects on the microbial community and the degradation of this compound. The soil samples were flooded or enriched with organic material or lime under laboratory conditions. The microbial activity and density as well as the total (mineralization) or partial hexachlorobenzene degradation (transformation into metabolites) were analyzed. The mineralization of 14C-hexachlorobenzene was analyzed by adding a 14C-hexachlorobenzene solution to soil samples, capturing the 14CO2, which was then quantified by liquid scintillation counting. The production of hexachlorobenzene metabolites was studied by extracting soil samples and analyzing the extracts by gas chromatography. The microbial activity was analyzed through measurement of the microbial respiration and the microbial density by counting the colony forming units (CFU) of the soil samples. The microbial activity was higher in samples enriched with sugarcane bagasse (maximum of 310 mg CO² g-1 soil) as well as the bacteria density (maximum of 152 x 10³ CFUs g-1 soil) and fungal density (maximum of 167 x 10³ CFUs g-1 soil). Neither the addition of earthworm humus, nor lime, nor the flooding of the samples affected the microbial activity or density. No mineralization or formation of hexachlorobenzene metabolites was observed. The addition of organic material therefore stimulated the microbial community, but did not result in hexachlorobenzene degradation.
bioremediation; mineralization; microorganisms; organic matter
