Title : Contamination of groundwater by nitrates, nitrites, ammonium and phosphate in the guelma-bouchegouf irrigated area (Northeastern Algeria)
The Guelma-Bouchegouf irrigated area is located in the north-east of Algeria, it extends about 80 km. It was commissioned in 1996, with an irrigable area of 9250 ha, it spreads on both banks of the Seybouse Wadi and it is subdivided into five autonomous distribution sectors. In order to assess the state of groundwater quality, physico-chemical and organic analyzes were carried out during the low water period in November 2017, at the level of fourteen wells in the Guelma-Bouchegouf irrigation area.The interpretation of the results of the chemical analyzes shows that the waters of the study area belong to two dominant chemical facies: sulphated-chlorinated-calcium and Sulfated-chlorinated-sodium. The mineral quality of the groundwater in the study area shows that Ca2+, Cl- and SO42- indicate little to significant values, Na+ and Mg2+ show moderate to significant mineralization of water, closely correlated with very high conductivities. The values of the recorded conductivities vary from 1360 μs / cm (P3) to 4610 μs / cm (P10). These important values are due to dissolved salts on the one hand and the leaching of fertilizers by irrigation water on the other hand.Nitrogen compounds (NO3-, NO2-, NH4+) and phosphates (PO43-) due mainly to the presence of salt rich evaporitic formations on one hand, and intensive agricultural activities on the other. NO3- and NH4+ show little to significant pollution throughout the study area. Phosphate represents a significant pollution, with excessive values far exceeding the allowable standard. With respect to ammonium, 87% of the sampling points present a little pollution and 13 % a significant pollution. Regarding phosphates, in the form of PO43-, groundwater in the study area represents a significant pollution; all values far exceed the allowable standard. It is expected that results of this work will help decision makers to take proper actions to protect groundwater quality in the study area.
Keywords: Groundwater, organic parameters, Standards, Pollution