ABSTRACT:Aras water basin is located in northwest of Iran. Sungun mine which is the largest open-cast copper mine of Iran is located in this region and is in the primary stages of extraction. The influence of mining activity on the quality of regional surface water has been taken in to consideration in this study. Accordingly, sampling was done from 5 local streams in the study area. In order to consider the effect of flow quantity on the amount of different parameters, sampling was done in July and November 2005 when the local streams had the minimum and maximum flow rate respectively. The concentrations of major anions and cations as well as As, Mo, Al, Cu, Cd, Cr, Fe, Mn and Zn were determined. The results showed that the concentrations of metallic ions like aluminum, chromium, copper, manganese, molybdenum and iron in samples collected in July are above USEPA (Environmental Protection Agency) limits; however, mentioned concentrations are lessened remarkably in the samples collected in November. This fact is justified considering dilution of ions concentration via more amount of water in November. The chemical characteristics of water compositions on the basis of major ion concentrations were evaluated on a Schoeller and Piper diagram. Accordingly, the dominant type of water in July and November is considered to be Ca-HCO 3 (calcium-bicarbonate type). Regarding Schoeller diagram, despite relatively high concentration of calcium, the current status of local surface water is acceptable for drinking purposes. By commencing mining excavation with designed capacity in near future, the minerals will come in to contact with air and water resulting in dissolution, especially in ponds, which, in turn, increases the concentration of heavy metals in surface water. Considering consequent uses of this water including drinking, irrigation, industrial, etc. precautions must be taken in to consideration.
