شوري، هيدروشيمي و كيفيت آب زيرزميني در دشت رباط-خرم آباد، غرب ايران

Salinity, Chemistry, and Quality of Groundwater in Robat-Khorramabad Plain, West of Iran

منطقه روستايي رباط در شمال شهر خرم آباد (غرب ايران) واقع شده است­. منابع آب زيرزميني موجود در منطقه براي مصارف شرب و كشاورزي استفاده قرار مي­شود. واحدهاي ليتولوژي اصلي منطقه عمدتاً شامل آهك، شيل، ماسه سنگ، كنگلومرا و مارن همراه با گچ و نمك است. به‌‌منظور ارزيابي كيفيت آب­هاي زيرزميني منطقه تعداد 15 نمونه از چشمه­ها و چاه­هاي منطقه برداشت شد و براي شاخص­هاي شيميايي­، كاتيون­ها­، آنيون­ها و عناصر فرعي تجزيه شد. براساس نتايج تجزيه­اي آب­هاي منطقه در گروه آب­هاي سخت تا خيلي سخت، بي مزه، لب شور تا خيلي شور قرار مي­گيرند و داراي ماهيت قليايي هستند. فراواني يون­هاي اصلي بدين صورت است Ca>Na>Mg>K و F

Groundwater salinization in semiarid regions is a limiting factor of use with strategic importance. In this study, the sources of salinity, chemistry, and quality of groundwater in Robat (Khorramabad plain, Iran) were identified through the geochemical methods. Using data analysis, the concentration of cations and anions were recognized with the order of Ca2+>Na+ >Mg2+>K+ and HCO3 -> Cl-> SO4 2+> NO3 -> F-, respectively. The high concentration of Na+, Cl-, and EC in some places is attributed to the gypsum and salty formations. In the study area, the salinization processes are identified by natural and artificial activities. The salinization mechanisms are identified by the natural dissolution of gypsum and salt from Gachsaran formation and man-made sources including boreholes drilled through Gachsaran Formation, salt mining, and agricultural activity. Also, the high concentration of nitrate is related to agricultural fertilizers and karstification effects. It is seen that the atmospheric NO3 -. HCO3 -, Ca2+, and Mg2+ concentration exceeded the standard limit in a few samples probably due to the calcareous formation. Besides, hydrochemical facies of the groundwater are Ca- HCO3 and Na-K-HCO3. Due to the presence of calcareous and salt bearing formations, 46%, 26%, and 20% of all samples show a higher concentration of Ca2+, Na+, and Mg2+, respectively, which exceed the permissible limits. Sulfate and fluoride concentrations are less than the permissible limits. However, due to the presence of calcareous formation, salt bearing formation, and use of agricultural fertilizers, 100%, 26%, and 20% of all samples show a higher concentration of HCO3 -, Cl-, and NO3 - than the permissible limits.