groundwater contamination by heavy metals in water resources of shiraz area

lack of sewage collection systems, percolation of surface waters, and seepage of wells have raised the groundwater table in shiraz area in the south of iran. the growing population generates environmental pollution resulting in the degradation of the quality of surface and groundwaters used for agriculture. inorganic and organic pollutants have been traced in shiraz water resources. heavy metals, as+2, cd2+, cr2+, fe2+, hg2+, and pb2+ have been reported as potential pollutants of both surface and groundwaters. the safety of groundwater supplies in shiraz was studied with respect to heavy metal concentrations. from 50 semi deep wells, which supply water for agricultural production, three water samples per well were examined to determin the physical and chemical characteristics of the water. the results of the study indicated that the concentration of cd2+, cr2+, fe2+, mn2+, and pb2+ exceed permissible values for crop production. a network of gallery systems was proposed for wastewater collection and the disposal of shiraz groundwater, to increase the water table depth in urban areas. it is estimated that about 100m m3 wastewater could be drained annually through the proposed gallery system which could be used for agricultural production. it is believed that mixing the drained waters from the proposed network of galleries with the agricultural water supplies will help control concentrations of heavy metals so they do not have serious acute impacts on agricultural production. the chronic effects of the impacts of water quality on agricultural production should be monitored temporarilly.