ORIGINAL ARTICLE Hydrochemical, isotopic and statistical characteristics of groundwater nitrate pollution in Damascus Oasis (Syria) Boulos Abou Zakhem • Rania Hafez Received: 31 December 2014 / Accepted: 1 March 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract A multi approach methodology using hydro- chemistry, 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 d 18 O values, clearly indicating that evaporation of irrigation water during infiltration and groundwater contamination. d 18 O–NO 3 - 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 sig- nificant PCs that explain 70 % of the variance. FI repre- sents the nitrates pollution of groundwater. FII exhibits the mineralization processes by interaction between ground- water and the host rocks. FIII and FIV indicate anthro- pogenic contamination by heavy metal. The proposed approaches have successfully illustrated and assessed the groundwater nitrate pollution. Keywords Hydrochemistry  Stable isotopes  Principal component analysis (PCA)  Shallow groundwater  Nitrate pollution Introduction Due to the scarcity of surface water in many regions around the world and the rapid increase in the population, there has been sharp increase in the potable water demand. Groundwater is becoming an important source of drinking water supply. The value of groundwater depends not only on its availability but also on its consistent good quality. Groundwater contamination is one of the most important environmental problems in the present world. Many previous studies on groundwater quality have shown that nitrate is derived from various point and non- point sources of pollution, such as agricultural, urban and industrial activities. The application of nitrogen-based fertilizers is the most extensive human source of NO 3 - in shallow groundwater systems. The amount of nitrate lea- ched from agricultural lands is strongly influenced by factors inherent in nature such as soil type, groundwater depth and climate conditions (Mikkelsen 1992). In groundwater and pore water that is strongly oxidizing, NO 3 - is the stable form of dissolved nitrogen. It moves with the groundwater and experiences no chemical trans- formation and little or no retardation. Very shallow groundwater in highly permeable sediment commonly contains considerable amounts of dissolved oxygen. It is in these hydrogeological environments that NO 3 - migrates large distances from its input areas (Shimojima and Sharma 1995). Groundwater nitrate pollution has become a widespread problem which affects all countries. It reduces the potential B. Abou Zakhem (&)  R. Hafez Geology Department, Atomic Energy Commission of Syria (AECS), Damascus, Syria e-mail: cscientific1@aec.org.sy 123 Environ Earth Sci DOI 10.1007/s12665-015-4258-1