CARACTERISATION DES PRINCIPALES EVAPORITES DES OASIS DU KAWAR (NORD-EST DU NIGER)

Abstract

Among the biophysical resources of the oases of Niger, salt occupies an important place. In the oases of Bilma located in the north-east of Niger, the artisanal exploitation of salts is done in the relic oases of fossil lakes and in the oases with brackish and outcropping water. This work aims to characterize the main salts of the Bilma oases in order to identify their suitability for human and animal consumption. The methodology is based on the sampling of salts in the saltworks and natronières then an X-ray analysis in a laboratory in Nigeria. Socioenvironmental surveys were carried out among oasis dwellers to inquire about their production system. The results show that the modes of access to these saltworks have remained ancestral. The electrical conductivity measurements indicate that the waters of the saltworks have a high conductivity compared to those of the natron ponds. X-ray analyzes show that the composition of cooking salts from Bilma (B1) is dominated by burkeite (60%), from Fachi (F1) by Thenardite (79.62%) and from Siguidin (S1) by d analcite (83.67%). Halite (NaCl) is present in these three cooking salts (B1, F1 and S1) in a variable proportion. The lick salts of the three sites are mainly composed of Thenardite and natrons (A1 and A2) by the trôna. The mineral B3 is mainly composed of Thenardite and quartz. These salts are used in human and animal food. They are also used as soap, remedy against certain diseases such as constipation, heartburn. To valorize these salts, it is necessary to modernize the exploitation systems so that they are consumed without any danger and become competitive on the markets.