Investigation of Arsenic Anomalies in Water Resources of Sahand Dam

In the last decades, hydro chemical investigation especially consideration of trace element pollution has changed to one of the main objectives of hydro chemical researches. Sahand Dam is one of the important dams of East Azarbaijan with 135 MCM storage located in southwest of Hashtroud city (Figure 1). Water storage of this dam supplies potable and industrial water demand of Hashtroud city. Furthermore, it is used for the irrigation of 11 hectares of the sector land. According to the importance of this water resource, the quality of dam reservoir water and the related surface water and ground water resources were monitored in recent eight years (1388-1381) by the University of Tabriz and East Azerbaijan regional water authority. The results of analyzed 308 water samples from ground and surface water resources and Dam storage of study area, which include major, minor and trace ions show arsenic anomalies (Table 1). From the hydrogeological point of view, geological formation can be divided into two main types: 1) Upper red formation deposit 2) Shand volcanic lava and tuff. Both of these formations are affected by major and minor faults. Field studies and obtained section from the geological formation of the study area show realgar and orpiment mineral (with respectively %70 and %61 of arsenic) in their joints.