en تخصصي Special Original articles <div dir="ltr" style="text-align: justify;"><strong><em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Introduction:</span></span></span></em></strong><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;"> Arsenic contamination of&nbsp; surface and groundwater has been categorizd among high profile&nbsp; environmental&nbsp; problems around the world. The matter is of most concern where unsafe water is used for drinking. Sahand region reservoir in northwest of Iran supplies water for drinking, industrial and agricultural purposes throught &nbsp;irrigation&nbsp; of 11000 hectares of lands. </span></span></span><br> <strong><em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Materials and Methods</span></span></span></em></strong><em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">:</span></span></span></em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;"> The hydrochemistry status of Sahand dam basin and arsenic plume distribution in water recourse was evaluated by analyzing 308 water samples from surface and ground water according to the standard methods. in addition, geological features information of basin were obtained based on recent site studies and field investigations.</span></span></span><br> <strong><em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Results:</span></span></span></em></strong><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Elevated concentrations of arsenic (range = 0-1440 ppb,<br> mean = 171.68 ppb) were detected in water basin and dam. According to the delineating evidences, regional geological background and volcanic activities can be considered as the main sources of the natural genesis of arsenic in the study area.</span></span></span><br> <strong><em><span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Conclusion:</span></span></span></em></strong> <span style="letter-spacing:.2pt;"><span style="font-family:times new roman,serif;"><span style="font-size:10.0pt;">Notable amounts of arsenic sulfide were recorded in seams, gaps , fractures of limestone, marl, sandstone and an overlying ferruginous conglomerate. Concentrations of arsenic varied seasonally highlithing the maximum concentration observed in autumn and early winter (December). Seasonal fluctuations can be probably attributed to changes in geochemical conditions in sediments at the bottom of reservoir.</span></span></span></div> Arsenic, Hydrology, Groundwater, Volcanic Activities, Dam, Iran. 209 220 http://jehsd.ssu.ac.ir/browse.php?a_code=A-10-1-47&slc_lang=en&sid=1 Mohammad Mosaferi No School of Health, Tabriz University of Medical Sciences, Tabriz, Iran. Sepideh Nemati No Urmia University of Medical Sciences, Urmia, Iran. Fereydoon Armanfar f_armanfar@yahoo.com Yes Regional Water Company of East Azerbaijan Province, Office of Water Resources Quality Conservation, Tabriz, Iran. Ataollah Nadiri No Department of Earth Sciences, Faculty of Science, University of Tabriz, Tabriz, Iran. Amir Mohammadi No Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.