Soil microbiological damages by overliming

Incubation studies were conducted to determine the influence of hydrophobis ed CaO added to the soil on the number of micro-organisms and their activit y. Soil that was contaminated with diesel fuel was mixed with hydrophobised CaO in a ratio of 10:1 in order to immobilise the pollutant. This procedur e is an usual method for the decontamination of polluted soils. The deliber ate lime surplus caused an increase of soil pH with a maximum value of pH 1 2.6. The high pH values decreased only very slowly within time. The treatme nt caused a decrease of the number of bacteria by about 99%. The population of actinomycetes and fungi was destroyed completely. The incubation study showed that actinomycetes and fungi were not able to recolonise the treated soil. The microbial activity reduced by the application of hydrophobised C aO recovered only incompletely.