Effect of industrial wastewater effluent containing heavy metals and phosphate on the bed soil of the zayandehrood river

 This research was conducted to determine the concentration of Zn, Cu, Pb, Ni, Cr and orthophosphates in the soil of the river bed from Zayandehrood dam to Gavkhoni wetland. 

 This cross-sectional study was conducted in the Zayandehrood river of Isfahan, central area of Iran. Seventeen points were sampled through the upstream, Zayandehrood Dam, and downstream, Gavkhooni Wetland, of the river. The samples were selected from soil of the river bed at certain locations during 6 months. Heavy metals and orthophosphates analysis was done by Atomic Absorption and Spectrophotometry methods, respectively. 

 The results indicated that concentration of heavy metals and orthophosphates increased from upstream to Choom bridge in downstream of the river and then decreased from this point to Govkhooni wetland. In the first sampling point, the concentration of Zn, Cu, Pb, Ni, Cr and orthophosphates were 29, 9, 51, 83, 49, and 570 mg/kg (dried weight). For Choom bridge it were 1413, 406, 289, 123, 86, and 104 mg/kg and in the wetland were 820, 24, 49, 68, 87, and 88 mg/kg (dried weight), respectively. 

 The metal concentration from the first point to Choom bridge has been increased and then has been decreased in the wetland. The maximum amount of Zn, Ni, Cu, and Pb in the river bed was higher than and closer to maximum allowed concentration of heavy metals in soil (mg/kg dried weight) and for Cr was within normal limits. Industrial plants located on the banks of the river, widening of the river in downstream and entering the drainages to the river are among effective factors in these changes.