Hydrochemical, isotopic and statistical characteristics of groundwater nitrate pollution in Damascus Oasis (Syria)

A multi approach methodology using hydrochemistry, environmental stable isotopes and multivariate statistical analysis, were carried out to identify the sources and distributions of groundwater nitrate pollution. Based on the spatial distribution of nitrate concentrations, nitrate pollution occurs mainly in the central part of the study area. Thus, the irrigated areas are likely to be the most affected by this pollution. More than 51.8 % of the sampled wells exceed the maximum contaminant level of 50 mg/L for drinking water. High nitrate levels are associated with isotopic enrichment of delta O-18 values, clearly indicating that evaporation of irrigation water during infiltration and groundwater contamination. delta O-18-NO3 (-) trends suggest isotopic distinct, non-point source origins which vary spatially and temporally, due to different degrees of evaporation, irrigation return flow and the intensive use of mineral and organic fertilizers and wastewater seepage. However, the anomalies of nitrates in the vicinities of Kabbass tannery are considered as point pollution by dumping of industrial wastewater into drainage network, without treatment. PCA showed the existence of four significant PCs that explain 70 % of the variance. FI represents the nitrates pollution of groundwater. FII exhibits the mineralization processes by interaction between groundwater and the host rocks. FIII and FIV indicate anthropogenic contamination by heavy metal. The proposed approaches have successfully illustrated and assessed the groundwater nitrate pollution.