Comparison of the physical and chemical properties of the bed and suspended sediments of the Roze-Chay river

River sediments are the major component of the aquatic ecosystems and play an important role in the nutrients cycle and contaminants transformation in river systems. Sediment particles are transported in the forms of the suspended and bed sediment depending on the river flow regime and the size distribution of the particles. Sediments in the river are in equilibrium with the pore water and river flow. Therefore, the composition of sediments strongly affects water quality and the biological activities in the aquatic systems. Release of the organic and inorganic contaminants and nutrients from the sediments to the river flow is mainly influenced by the physical and chemical properties of the sediments. Thus, understanding of the basic physical and chemical properties of river sediments is essential for sustainable management of the watershed. The aim of this study was evaluate and compare the physical and chemical properties of the suspended and bed sediments of the Roze-Chay river in the Urmia region.
Total of the 19 bed sediments were collected along the river. Bed sediments were sampled from three parts of the river including up-stream (6 samples), mid-stream (6 samples), and down-stream (7 samples). In addition, six suspended sediments were sampled from the river during a flood event. Sediment samples were passed through a 2000 micron sieve and were analyzed for their basic physical and chemical properties. Hierarchical cluster analysis and principle component analysis were preformed for grouping the sediment samples and identifying the most effective properties of them.
Results indicated that the sand and silt particles are very dominant in bed and suspended sediments, respectively. The average silt and very fine sand content in bed sediments were 15.8 and 15.5 percents, while the silt and very fine sand particles content in suspended sediments were 44 and 25 percent, respectively. However, bed sediment have coarse texture due to their higher sand content in comparison with suspended sediments. The average values of organic matter and electrical conductivity of bed sediments were 1.7 and 2.5 times greater than the suspended samples. The organic matter content in up-stream bed sediments were higher than the middle and downstream parts, which may due to the discharge of the domestic sewage in this part of the watershed. Principle component and the hierarchical cluster analysis showed that the organic matter, EC, and particle size distribution are the most effective properties of the sediments.
Discharge of the domestic sewage to the river bed may has led to the accumulation of the organic matter and soluble salts in the bed sediments of the upstream part. As a result, the basic physical and chemical properties of the upstream bed sediments are different from the middle and downstream parts. Preventing the entry of the sewage into the river bed especially at the upstream part has an essential role in sustainable management of the Roze-chay river ecosystem. Multivariate analysis of the sediment samples revealed that there was a significant difference between the properties of the suspended and bed sediments.