Impact of pollution by the hydrocarbons on the biological activity of soils in Ouagadougou, Burkina Faso

The microbial activity estimated by respirometry test method made it possible to measure the quantity of CO2 produced per day, from four soils polluted at different degrees by hydrocarbons. These samples have been wet to 2/3 of their maximal capacity of retention and incubated at 30°C for 30 days. The quantity of CO2 released and measured shows a high value (83.97 mg/100 g of soils against 36.05 mg/100 g of soils) in soils highly polluted by hydrocarbons treated without cow dung. We get higher values (148.98 mg/100 g of polluted soils against 66.52 mg/100 g of not contaminated soils) when the cow dung is used as a ferment. The total aerobic mesophilic flora in the samples of soils has been counted on the nutritive agar. The result is that the total aerobic mesophilic flora varied from 1×104 Colony Forming Unit (CFU) to 50 × 104 CFU before treatment and from 5×104 CFU to 420×104 CFU after 30 days of treatment. During the treatment of the soils, the bacteria and molds microflora increases with time while yeasts disappear progressively. Key words: Respirometry, microorganisms, contaminated soils, hydrocarbons.