Metal Pollution Assessment of Sediment and Water in Al-Ghadir River: Role of Continuously Released Organic Matter and Carbonate and Their Purification Capacity

During the discharge of metals in the aquatic environment, metals are partitioned between the sediment and the water column phases. Further partitioning of metals occurs within the sediment chemical fractions. The present study focuses on one of the middle eat rivers, Al-Ghadir which is the smallest and the most polluted and found in the most populated region in Lebanon. The aim of this study was to integrate hydrochemical and sediment data- in order to evaluate the distribution pattern of the pollution of Al-Ghadir River. Bed sediments and water were collected from five locations in one dry season (Octobre 2010) and analyzed for more than 40 parameters, including (i) those of the chemical and the physico-chemical nature and (ii) those reporting the pollution caused by the heavy metals partitioned between the sediment and the water column phases by applying a sequential chemical fractionation scheme to the <75 μm sieved sediment fraction. The quality of waters for different uses has been tested and the state of sediments pollution was evaluated by comparison with general quality standards. Data showed that the highest percentages of total metal content in sediment are for: Fe and Mn in the residual and in the Fe/Mn oxides fractions, Cu in the oxidizable fraction, Cd and Zn in the carbonate and in the Fe/Mn oxides fractions, Pb and Cr in the Fe/Mn oxides fraction. Based on the geoaccumulation indices (I geo), the river sediments are considered to be moderately polluted with the measured metals.