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Background and Objective: This research tries to analyze the spatial distribution and trend of arsenic level changes in the underground water resources of the Sirjan basin, and also to evaluate and analyze the factors affecting the concentration of this element in these water resources. Materials and Methods: Sampling of underground water sources in the study area was done by systematic-random method and arsenic concentration was done by ICP)MS method in the laboratory. Also, to evaluate the factors affecting the concentration of arsenic in the underground water resources of Sirjan bathe sin, the method of land systems analysis was used. Results: The results of the research show that the amount of arsenic in all samples is higher than the Guidelines provided by the World Health Organization so the amount of this element in the underground water sources of the study area varies between 30 and 390 µg/L. Samples No. 9, 13, and 16, which are located in the deepest parts of the basin, have the highest amount of arsenic. For this reason, the durability of water in this part of the basin increases. This reduces the intensity of the current. As a result, according to the cumulative effect law, this process can lead to an increase in arsenic concentration. Conclusion: The evaluation of changes in the concentration of arsenic in the underground water resources of the study area indicates that the concentration of this element had a high increasing trend. According to the results, the location of the studied area in the center of hydrothermal and geothermal processes (copper mineralization belt in Iran), the cumulative effect, and the effect of pH on the absorption and desorption of arsenic are among the most important factors affecting the increase of arsenic in the underground water resources of Sirjan Basin. [ABSTRACT FROM AUTHOR]

The Chahpalang iron occurrence is located 90 km northeast of Ardakan city in Yazd province and Central Iran structural zone. The rock units in the study area consist of meta- volcanics, recrystallized carbonates and schists. The ore body is hosted by metavolcanics and carbonate rocks. Magnetite (two types), hematite (three types) are associated with minor amount of pyrite and secondary minerals including goethite, limonite as ore minerals. The orebody exposed as disseminated, veins and rare small lenses in the study area. Disseminated, massive, corrosion, brecciated, replacement, network are the textures of mineralization and the alteration halos are chloritization, epidotization and silicification. Total iron values vary between 28 to 91 wt% in the samples studied. The low values of Cr, V as well as Ni- Co diagram confirm hydrothermal origin of Chahpalang iron occurrence. The REE total values are between 10 and 110 ppm and distribution pattern diagram of these elements indicate the decreasing trend from LREEs to HREEs, pointing to the fractionation of these elements in the hydrothermal process. Negative Ce and positive Eu anomalies and the REE calculated ratios demonstrate the similarity of Chahpalang iron index with hydrothermal deposits. [ABSTRACT FROM AUTHOR]