Investigation of parameters affecting mercury distribution and mobility in water resources and sediments of Sefid Rud river

In order to study mercury contamination and the factors controlling its distribution in Sefidrud basin, 344 sampels were collected from river sediments, surface and ground waters. Water samples were analyzed for determining Hg concentration and physicochemical parameters such as pH, TDS, temperature, DO, biological oxygen demand (BOD) and chemical oxygen demand (COD). Sediment samples also analyzed for Hg, Al, Fe and Mn concentration. The correlation coefficient showed positive and negative relationships among the parameters. An appreciable significant correlation was found among TDS, pH, DO and the amount of rainfall with mercury in surface water (river), while the most correlated parameters with mercury in groundwater, were rainfall, TDS and temperature. Using distribution map of mercury in sediment and surface waters indicated that Hg trends in sediment and surface waters (except for kiashahr station) are opposite to each other. The results also showed that, Fe, Al and Mn play an important role in reducing the concentration of mercury in water samples, while the behavior of sediments for mercury absorption is strongly depended on the physicochemical properties of water. Therefore, the distribution of mercury in the Sefid rud basin is largely influenced by parameters such as rainfall, sediment composition and physicochemical properties of water (specially TDS, pH and DO).