In this study, arsenic concentration and pollution in water resources of Pangi area (Kadkan, NW Torbat Hydarieh), adjacent to Sarhang- Golbou ophiolitic zone, is investigated. Results of this study indicate high concentrations of arsenic in local water resources as arsenic concentration is 12 times greater than standard values in Golbou. Aquifer lithology, hydrological gradient, and water geochemistry of Roudeshour and adjacent areas show that the same processes control arsenic concentrations in surficial and ground water resources. As-bearing sulfide minerals especially pyrite and arsenopyrite are the main origin of arsenic in water resources. In spite of that, arsenic remaining time and mechanism of diffusion in water phase is controversial. According to geochemical studies, arsenic can be released at and close to surface of aquifer and then during geochemical reactions it can be transferred to depth. States of arsenic diffusion in aqueous phases depend on oxidation of As-bearing solid materials and displacement of antagonistic ligands. In presence of sulfides and reducing conditions, thioarsenic is dominant form of arsenic but in oxidizing conditions arsenate is dominant form. Thus, solution of Fe oxy-hydroxides together with arsenic diffusion, is the main agent of high concentration of arsenic in local water resources.

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