[Well water pollution in the Khombole district: research on the contamination by organochlorine pesticide residues and organic substances (feces)].

The study realized in the district of Khombole (SENEGAL) has permit to estimate the contamination levels of wells waters used by the populations. The research and the dosage of the organichlorine pesticide residues, nitrites and nitrates and microbiologic analysis have been done on 19 wells chosen after a drawning of lots. The organochlorine pesticide residues which have been found prove that the wells are permanently exposed to these chemical substances which don't constitute nevertheless a major risk for the populations health. The results of our research proved also that there is a real risk of intoxication with the nitrogen oxides. In effects more than 50% of the wells have revealed nitrates contents up to the indicative value (25 mg/l). As for the nitrates, with a few exceptions (5/18), the contents are superior to the authorized norm (0.1 mg/l). By another way the bacteriologic analysis has revealed in the one hand a DBT (Total Bacterian Count) up to 10,000 germs/l for all the wells, and in the other hand the presence of Escherichia coli, Enterococcus faecalis that confirm a faecal contamination.