Ecological Risk Assessment of Sediments in the River Environment (Case Study: Karaj River)

Rivers are one of the most important sources of surface water in the world. The purpose of this research is to investigate the contamination of Karaj River sediments with heavy metals using sediment quality indices, evaluate the effects of pollution on the environment, and provide solutions to reduce pollution and its aftereffects. To achieve this goal, the sediments of the Karaj River bed were sampled at nine stations, and the total concentration of heavy elements in the samples was measured by the ICP device. Eventually, the sediment quality indicators for each of the metals were analyzed separately. The results showed that the Karaj River suffered little pollution in terms of bed sediment contamination with heavy metals, but the role of human activities in producing this amount of pollution cannot be neglected. Urban and rural activities, as a result of their effluents and sewage leaking into the river environment, construction and road construction projects in the region, land use changes in the river's boundaries and margins, and the people's lack of awareness in the region regarding the environmental effects of metal pollution. Inadequacy in proper education and culture in relation to tourism and environmental protection are among the destructive and polluting human factors in the area of Karaj River, which caused an increase in copper contamination up to 2.36 as well as the Pollution Load Index to the point of 0.76 in downstream stations.