NITRITE CONTENT IN GROUNDWATER RESOURCES IN NIGER: CASE OF DISCONTINUOUS AQUIFERS OF THE DAMAGARAMMOUNIO BASEMENT

Abstract

The base of Damagaram-Mounio outcrops in the eastern part of the Zinder region. In this zone, the aquifers are discontinuous and the groundwater resources are located in fractured, fissured and / or altered horizons of granite (Older granites) and metamorphic formations of the Pan-African and young cracked granites (Younger granites) . These aquifers are mainly captured by boreholes whose failure rates, very high, can exceed 50%. In addition, the positive borehole flows are less than 2 m3 / h at more than 85% of them. Thus, the problem of water resources arises acutely. In this densely populated area, this lack of water to feed the population is aggravated by high levels of nitrites. In fact, these levels greatly exceed the standards of drinking water for human consumption hence the present study, the main objective of which is to characterize the nitrite contents in the groundwater resources of the area. The methodological approach based on the inventory of hydraulic structures capturing the boreholes in the base and the analysis of the physico-chemical parameters of the water from several boreholes, made it possible to establish that 32% of the water from the sampled boreholes has nitrite contents. , exceeding the WHO standard set at 0.1 mg / L, therefore, these waters are unfit for human consumption. This study made it possible to highlight waters with high nitrite contents which are characterized by values ​​greater than 1 mg / L. This concerns borehole water from localities such as: Bourbourwa, Midik and that of ZengonSoumagaila. The high nitrite contents observed in the groundwater in the area may be linked to an organic pollution phenomenon. Furthermore, no significant correlation was observed between the nitrite contents and the values ​​of the electrical conductivity of the groundwater in the area.