Spatial and temporal variations of selected indices of water and sediment quality in Zayande-rood River, Isfahan, Iran

Restoration of Zayande-Rood River which is threatened by human activities requires perpetual monitoring of water and sediment quality, on the one hand, and identification of different polluting sources, on the other. This paper reviews some essential findings of previous works about the contamination state of Zayande-rood river. Spatial and temporal variation of some quality indicators (temperature, pH, total dissolved solids, electrical conductivity, total nitrogen and phosphorous, Na, Ca, K, Cl, Cd, Fe, Ni, Pb, sulfate and bicarbonate) measured in river water are discussed. In addition, some properties of point-source pollutants are presented. Variation of total and soluble concentration of some heavy metals in polluting sources and riverbed sediments are discussed. Moreover, the different chemical forms of these heavy metals are assessed. Results show that most of polluting agents in the point-source pollutants are above thecritical levels. However, due to the low rate of swage flow, no significant effects were observed in the river quality. Among the point-source pollutants, South Isfahan Refinery is the most contaminating source. The variation of cations, anions, salinity, and total dissolved solids are highly correlated; these values increase gradually towards the eastern region of Isfahan ( Baraan and Roodasht). After the introduction saline drainage water of farmlands, these values increase sharply. High concentration of nitrogen in the lowermostside of the river witnesses the unsustainable agricultural management of the region, especially, high application of chemical fertilizers. Heavy metals concentration only increase in the lowermost side of the river; however, the absolute values of these metals are low throughout the river. In contrast, high concentration of soluble and exchangeable forms of heavy metals in riverbed sediments warns the potential hazards of river water pollution