Deterioration of the quality of ground water in agricultural region. Case Mitidja (Algeria)

Abstract

In Algeria the plain of Mitidja, famous for the fertilization of its soil, on overuse, is exposed to pollution due particularly to fertilizers and other phytosanitary. The spatio-temporal distribution of the concentrations of major ions, namely nitrates, would explain the transfer and circulation mechanisms of these elements within groundwater .The disparity in nitrate levels shows exposure of the Mitidja aquifer to pollution over its entire extent. The geological origin of the high concentrations of nitrates in places cannot alone explain this distribution. The levels are higher during recharge and irrigation due to the leaching effect of agricultural soils. The use of highly nitrogenous chemical fertilizers in agriculture, compared to the evolution of piezometric levels, causes a significant increase in nitrate concentrations due to their transport from the surface to the aquifer. The subterranean waters of the Quaternary aquifer in the Mitidja show in certain areas concentrations greater than 250 mg / l (Hamiz region in the eastern part of the Mitidja). This high concentration results mainly from irrigation (market gardening).